an54af ci linear reguladores
TRANSCRIPT
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Application Note 54
March 1993
Power Conversion from Milliamps to Amps at Ultra-High
Efficiency (Up to 95%)
and LTC are registered trademarks and LT is a trademark of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
Dimitry Goder
Randy Flatness
INTRODUCTION
High efficiency is frequently the main goal for powersupplies in portable computers and hand-held equipment.Efficient converters are necessary in these applications to
minimize power drain on the input source (batteries, etc.)and heat buildup in the power components, allowing forsmaller, lighter, and longer-lived systems. Power conver-sion efficiency must be in the 90% range in order to meetthese goals. This application note features power supplycircuits that satisfy these design requirements and attainhigh efficiency over a wide operating range.
The recent development of the LTC1142, LTC1143,LTC1147, LTC1148, and LTC1149 makes ultra-high effi-ciency conversion possible. In addition, the LTC1148,LTC1149, and LTC1142 are synchronous switching regu-
lators, achieving high efficiency conversion at outputcurrents in excess of 10A. These controllers feature a
current mode architecture that has automatic BurstModeTMoperation at low currents. This technology makes90% efficiencies possible at output currents as low as
10mA, maximizing battery life while a product is in sleepor standby mode.
These ultra-high efficiency converters also implementconstant off-time architecture, fully synchronous switch-ing and low dropout regulation. All these features makethis series of converters a really excellent choice for a vastvariety of applications.
Achieving high efficiency is one of the primary goals ofswitching regulator design. Every application circuit shownin this note includes detailed efficiency graphs. Almost all of
the magnetic parts used in the circuits are standard prod-ucts, available off-the-shelf from various manufacturers.
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Application Note 54
AN54-2
TABLE OF CONTENTS
Buck
LTC1148: (5V-14V to 5V/1A) Buck Converter with Surface Mount Technology ................................................................Figure 1 AN54-3LTC1148: (5V-14V to 5V/2A) Buck Converter .................................................................................................................. Figure 2 AN54-4LTC1148: (5V-14V to 5V/2A) High Frequency Buck Converter with Surface Mount Technology...................................... Figure 3 AN54-5LTC1148: (4V-14V to 3.3V/1A) Buck Converter with Surface Mount Technology............................................................. Figure 4 AN54-6LTC1148: (4V-14V to 3.3V/2A) Buck Converter with Surface Mount Technology............................................................. Figure 5 AN54-7LTC1148: (5V to 3.3V/5A) High Efficiency Step-Down Converter ..................................................................................... Figure 6 AN54-8LTC1148: (5V to 3.5V/3A) High Efficiency Step-Down Converter .................................................................................... Figure 7 AN54-9LTC1149: (10V-48V to 5V/2A) High Voltage Buck Converter........................................................................................... Figure 8 AN54-10LTC1149: (10V-48V to 5V/2A) High Voltage Buck Converter with Large P-Channel and N-Channel MOSFETs ................ Figure 9 AN54-11LTC1149: (10V-48V to 3.3V/2A) High Voltage Buck Converter....................................................................................... Figure 10 AN54-12LTC1149: (10V-48V to 12V/2A) High Voltage Buck Converter........................................................................................ Figure 11 AN54-13LTC1149: (16VRMSto 13.8/10A) Buck Converter ........................................................................................................... Figure 12 AN54-14LTC1149: (32VRMSto 27.6V/5A) Buck Converter ........................................................................................................... Figure 13 AN54-15LTC1147: (5V-14V to 5V/1A) Buck Converter with Surface Mount Technology .............................................................. Figure 14 AN54-16LTC1147: (4V-14V to 3.3V/1A) Buck Converter with Surface Mount Technology ...........................................................Figure 15 AN54-17
LTC1147: (4V-8V to 3.3V/1.5A) Buck Converter with Surface Mount Technology .......................................................... Figure 16 AN54-18LTC1148: (10V-14V to 5V/10A) High Current Buck Convert .......................................................................................... Figure 17 AN54-19LTC1149: (12V-36V to 5V/5A) High Current, High Voltage Buck Converter................................................................... Figure 18 AN54-20LTC1149: (12V-48V to 5V/10A) High Current, High Voltage Buck Converter................................................................. Figure 19 AN54-21LTC1149: (32V-48V to 24V/10A) High Current, High Voltage Buck Converter ............................................................... Figure 20 AN54-22LTC1143: (5.2V-14V to 3.3V/2A and 5V/2A) Dual Buck Converter ................................................................................ Figure 26 AN54-28LTC1148HV-5: (5.2V-18V to 5V/1A) High Voltage Buck Converter ................................................................................ Figure 27 AN54-29LTC1148HV-3.3 (4V-18V to 3.3V/1A) High Voltage Buck Converter .............................................................................. Figure 28 AN54-30LTC1148HV: (12.5V-18V to 12V/2A) High Voltage Buck Converter ............................................................................... Figure 29 AN54-31LTC1142: (6.5V-14V to 3.3V/2A, 5V/2A, 12V/0.15A) Triple Output Buck Converter ...................................................... Figure 30 AN54-32LTC1142HV: (6.5V-18V to 3.3V/2A, 5V/2A, 12V/0.15A) High Voltage Triple Output Buck Converter ............................ Figure 31 AN54-34Single LTC1149: Dual Output Buck Converter ............................................................................................................... Figure 35 AN54-38LTC1148: (8V-15V to 5V/2A) Constant Frequency Buck Converter ................................................................................ Figure 36 AN54-39
LTC1148: (4.5V-6.5V to 3.3V/2A) Constant Frequency Buck Converter......................................................................... Figure 37 AN54-40Buck-Boost and Inverting Topologies
LTC1148: (4V-14V to 5V/1A) SEPIC Converter .............................................................................................................. Figure 21 AN54-23LTC1148: (4V-14V to 5V/0.5A, 5V/0.5A) Split Supply Converter ................................................................................. Figure 22 AN54-24LTC1148: (4V-10V to 5V/1A) Positive-to-Negative Converter ...................................................................................... Figure 23 AN54-25LTC1148: (5V-12V to 15V/0.5A) Buck-Boost Converter .............................................................................................. Figure 24 AN54-26
Boost
LTC1148: (2V-5V to 5V/1A) Boost Converter ................................................................................................................. Figure 25 AN54-27
Battery Charging Circuits
LTC1148: High Efficiency Charger Circuit ...................................................................................................................... Figure 32 AN54-35LTC1148: High Voltage Charger Circuit ......................................................................................................................... Figure 33 AN54-36
LTC1142A: High Efficiency Power Supply Providing 3.3V/2A with Built-In Battery Charger ......................................... Figure 34 AN54-37Appendix A
Topics of Common Interest ........................................................................................................................................................... AN54-40
Appendix B
Suggested Manufacturers ............................................................................................................................................................. AN54-42
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Application Note 54
LTC1148: (5V-14V to 5V/1A) Buck Converter withSurface Mount Technology
A basic LTC1148 application is shown in Figure 1A. This isa conventional step-down converter that provides 5V out-
put at 1A maximum output current. All the componentsused are surface mounted and no heat sink is required.During Q1 on-time, inductor L1's current is sensed by R2and monitored by an internal current sensing comparator.To filter out noise from the current sense waveform, C6 isadded to the circuit. When the current ramp reaches apreset value, Q1 is turned off, and a clamp diode D1 startsconducting for a short period of time, until the internalcontrol logic senses that Q1 is completely off. ThenNDRIVEoutput goes high turning Q2 on, which shorts outD1. This provides synchronous rectification and signifi-cantly reduces conduction losses during Q1s off-time.
This regulator has a constant off-time defined by the timingcapacitor C5. To control the output, on-time is varied,
changing the operating frequency and therefore, the dutycycle. If the input voltage is reduced, frequency decreaseskeeping output voltage at the same level. Q1s on-timestretches to infinity with low input voltage, providing 100%
duty cycle and very low dropout. Under dropout condi-tions, the output voltage follows the input, less any resis-tive losses in Q1, L1 and R2.
Under conditions of light output currents, the regulatorenters Burst Mode operation to ensure high efficiency.Continuous operation is interrupted by an internal voltagesensing comparator with built-in hysteresis. in this modeboth Q1 and Q2 are turned off and the comparator monitorsdecreasing output voltage. When the output capacitordischarges below a fixed threshold, operation resumes fora short period of time bringing the output voltage back to
normal. Then the regulator shuts down again conservingquiescent current. Under Burst Mode operation the outputripple is typically 50mV as set by the hysteresis in thecomparator.
Kool Mis a registered trademark of Magnetics, Inc.
Figure 1A. LTC1148: (5V-14V to 5V/1A) Buck Converter with Surface Mount Technology
AN54 F01AC1 (Ta)
C3 AVX (Ta) TPSD226K025R0200 ESR = 0.200 IRMS= 0.775AC7 AVX (Ta) TPSE227K010R0080 ESR = 0.080 IRMS= 1.285AQ1 SILICONIX PMOS BVDSS= 20V RDSON= 0.100 CRSS = 400pF Qg= 50nCQ2 SILICONIX NMOS BVDSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 30nCD1 MOTOROLA SCHOTTKY VBR = 40V
ITH
CT
SGND PGND
LTC1148-5
VINPDRIVE
SENSE +
SENSE
NDRIVE
+
C60.01F
+
VIN5V TO 14V
C11F
R11k
C43300pFX7R
C5390pFNPO
10
4
1
8
7
14
Q1Si9430DY
Q2Si9410DY
D1MBRS140T3
C322F 225V
100H
R20.1
5V1A
C7220F 10V
3
11
12
SHUTDOWN
6
C20.1F
+
L1
1
2
4
3
R2 KRL SP-1/2-A1-0R100J Pd = 0.75W
L1 COILTRONICS CTX100-4 DCR = 0.175Kool MCORE
ALL OTHER CAPACITORS ARE CERAMIC
QUIESCENT CURRENT = 180ATRANSITION CURRENT (Burst Mode OPERATION/CONTINUOUS OPERATION) = 200mA
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Application Note 54
AN54-4
Figure 1B shows efficiency versus output current for threedifferent input voltages. Generally speaking, efficiencydrops as a function of input voltage due to gate chargelosses and LTC1148 DC bias current. The curves converge
at maximum output current as these losses become lesssignificant.
OUTPUT CURRENT (A)
0.00150
EFFICIENCY(%)
70
80
90
100
0.01 0.1 1
AN54 F01B
60
VIN= 6V
VIN= 10V
VIN= 14V
Figure 1B. LTC1148: (5V-14V to 5V/1A) Buck ConverterMeasured Efficiency
Figure 2A. LTC1148: (5V-14V to 5V/2A) Buck Converter
AN54 F02A
C1 (Ta)
C3 AVX (Ta) TPSD226K025R0200 ESR = 0.200 IRMS= 0.775A
C7 AVX (Ta) TPSE227K010R0080 ESR = 0.080 IRMS= 1.285A
Q1 SILICONIX PMOS BVDSS= 20V RDSON= 0.100 CRSS = 400pF Qg= 50nC
Q2 SILICONIX NMOS BVDSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 30nC
D1 MOTOROLA SCHOTTKY VBR = 40V
R2 KRL SL- 1-C1-0R050J Pd = 1W
L1 COILTRONICS CTX62-2-MP DCR = 0.040 MPP CORE (THROUGH HOLE)
ALL OTHER CAPACITORS ARE CERAMIC
ITH
CT
LTC1148-5
VIN
SENSE +
SENSE
+
C60.01F
+
VIN5V TO 14V C1
1F
R11k
C43300pFX7R
C5470pFNPO
10
4
1
8
7
14
Q1Si9430DY
Q2Si9410DY
D1MBRS140T3
C322F 325V
L162H
R20.05
5V2A
C7220F 2 10V
QUIESCENT CURRENT = 180A
TRANSITION CURRENT (Burst ModeOPERATION/CONTINUOUS OPERATION) = 400mA
3
11
12
SHUTDOWN
6
C20.1F
+
SGND PGND
PDRIVE
NDRIVE
LTC1148: (5V-14V to 5V/2A) Buck Converter
A step-down regulator with 2A output current capability isshown in Figure 2A. To provide higher output power levelsthe sense resistor value is decreased, thus increasing thecurrent limit. This also increases maximum allowableripple current in the inductor, so its value can be reduced.Note that timing capacitor C5 is changed to optimizeperformance for a standard inductor value. In this FigureC7 consists of two parallel capacitors ensuring minimumcapacitance requirement for all conditions. A circuit boardhas been laid out for this circuit and has subsequentlybeen thoroughly tested under full operating conditionsand optimized for mass production requirements. A Ger-ber file for the board is available upon request.
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Application Note 54
OUTPUT CURRENT (A)
0.00150
EFFICIENCY(%)
70
80
90
100
0.01 0.1 2
AN54 F02B
60
VIN= 6V
VIN= 10V
VIN= 14V
1
Figure 2B. LTC1148: (5V-14V to 5V/2A) Buck ConverterMeasured Efficiency
LTC1148: (5V-14V to 5V/2A) High Frequency BuckConverter with Surface Mount Technology
Figure 3A presents essentially the same circuit as Figure2A, but implementing changes to operate at a higher
frequency. Timing capacitor C5 is reduced to achievehigher switching rate. This approach allows the use of asmaller value inductor with surface mount technology,resulting in a more compact design.
C1 (Ta)
C3 AVX (Ta) TPSD226K025R0200 ESR = 0.200 IRMS= 0.775AC7 AVX (Ta) TPSE227K010R0080 ESR = 0.080 IRMS= 1.285AQ1 SILICONIX PMOS BVDSS= 20V RDSON= 0.100 CRSS = 400pF Qg= 50nCQ2 SILICONIX NMOS BVDSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 30nCD1 MOTOROLA SCHOTTKY VBR = 40V
R2 KRL SL-1-C1-0R050J Pd = 1W
L1 COILTRONICS CTX33-4 DCR = 0.06Kool MCORE
ALL OTHER CAPACITORS ARE CERAMIC
ITH
CT
LTC1148-5
VIN
SENSE +
SENSE
+
C60.01F
+
VIN5V TO14V
C11F
R11k
C43300pFX7R
C5220pFNPO
10
4
1
8
7
14
Q1Si9430DY
Q2Si9410DY
D1MBRS140T3
C322F 325V
33H
R20.05
5V2A
C7220F 2 10V
QUIESCENT CURRENT = 180ATRANSITION CURRENT (Burst ModeOPERATION/CONTINUOUS OPERATION) = 400mA
3
11
12
SHUTDOWN
6
C20.1F
+
L1
1
2
4
3
AN54 F03A
SGND PGND
PDRIVE
NDRIVE
Figure 3A. LTC1148: (5V-14V to 5V/2A) High Frequency Buck Converter with Surface Mount Technology
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Application Note 54
AN54-6
Figure 4A. LTC1148: (4V-14V to 3.3V/1A) Buck Converter with Surface Mount Technology
Let us compare efficiency graphs in Figures 2B and 3B.Gate charge losses are directly proportional to operatingfrequency, and as a result the efficiency of Figure 3A is
decreased. However, the effect is most noticeable at highinput voltages and low currents. At maximum load I2Rlosses dominate so that the regulator performance variesonly slightly. These two circuits illustrate the fact that best
overall efficiency is reached at moderate frequencies. Theyrepresent a nice example of compromising between regu-lator compactness and efficiency.
AN54 F04A
C1 (Ta)
C3 AVX (Ta) TPSD226K025R0200 ESR = 0.200 IRMS= 0.775AC7 AVX (Ta) TPSE227K010R0080 ESR = 0.080 IRMS= 1.285AQ1 SILICONIX PMOS BVDSS= 20V RDSON= 0.100 CRSS = 400pF Qg= 50nCQ2 SILICONIX NMOS BVDSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 30nCD1 MOTOROLA SCHOTTKY VBR = 40V
R2 KRL SP-1/2-A1-0R100J Pd = 0.75W
L1 COILTRONICS CTX100-4 DCR = 0.175Kool MCORE
ALL OTHER CAPACITORS ARE CERAMIC
ITH
CT
LTC1148-3.3
VIN
SENSE +
SENSE
+
C60.01F
+
VIN4V TO 14V C1
1F
R11k
C43300pFX7R
C5560pFNPO
10
4
1
8
7
14
Q1
Si9430DY
Q2Si9410DY
D1MBRS140T3
C322F 225V
100H
R20.1
3.3V1A
C7220F 10V
QUIESCENT CURRENT = 180ATRANSITION CURRENT (Burst ModeOPERATION/CONTINUOUS OPERATION) = 250mA
3
11
12
SHUTDOWN
6
C20.1F
+
L1
1
2
4
3
SGND PGND
PDRIVE
NDRIVE
OUTPUT CURRENT (A)
0.00150
EFFICIENCY(%)
70
80
90
100
0.01 0.1 1
AN54 F03B
60
VIN= 6V
VIN= 10V
VIN= 14V
2
Figure 3B. LTC1148: (5V-14V to 5V/2A) High FrequencyBuck Converter Measured Efficiency
LTC1148: (4V-14V to 3.3V) Buck Converters withSurface Mount Technology
Figures 4A and 5A show application circuits for theLTC1148-3.3 which provides a fixed 3.3V output. Thecircuits deliver 1A and 2A output currents, and use exactlythe same circuit configuration and component values asFigures 1A and 2A. Even though the LTC1148 can achievelow dropout, the minimum input voltage is limited to 4V tomeet requirements for power MOSFET gate drive, and toensure proper operation of the LTC1148 internal circuitry.
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Application Note 54
Low output voltage causes efficiency degradation at lightloads when the chips DC supply current and gate chargecurrent play major parts in total losses. Figures 4B and
Figure 5A. LTC1148: (4V-14V to 3.3V/2A) Buck Converter with Surface Mount Technology
5B illustrate this point as the efficiency falls off below10mA output current. High input voltage compounds theproblem.
Figure 4B. LTC1148: (4V-14V to 3.3V/1A) Buck ConverterMeasured Efficiency
OUTPUT CURRENT (A)
0.00150
EFFICIENCY(%)
70
80
90
100
0.01 0.1 1
AN54 F04B
60
VIN= 5V
VIN= 10V
VIN= 14V
OUTPUT CURRENT (A)
0.00150
EFFICIENCY(%)
70
80
90
100
0.01 0.1 2
AN54 F05B
60
1
VIN= 5V
VIN= 10V
VIN= 14V
Figure 5B. LTC1148: (4V-14V to 3.3V/2A) Buck ConverterMeasured Efficiency
AN54 F05A
C1 (Ta)C3 AVX (Ta) TPSD226K025R0200 ESR = 0.200 IRMS= 0.775A
C7 AVX (Ta) TPSE227K010R0080 ESR = 0.080 IRMS= 1.285A
Q1 SILICONIX PMOS BVDSS= 20V RDSON= 0.100 CRSS = 400pF Qg= 50nC
Q2 SILICONIX NMOS BVDSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 30nC
D1 MOTOROLA SCHOTTKY VBR = 40V
R2 KRL SL-1-C1-0R050J Pd = 1W
L1 COILTRONICS CTX50-2-MP DCR = 0.032MPP CORE (THROUGH HOLE)
ALL OTHER CAPACITORS ARE CERAMIC
ITH
CT
LTC1148-3.3
VIN
SENSE +
SENSE
+
C60.01F
+
VIN4V TO 14V C1
1F
R11k
C43300pFX7R
C5470pFNPO
10
4
1
8
7
14
Q1Si9430DY
Q2Si9410DY
D1MBRS140T3
C322F 325V
L1
50H
R2
0.05
3.3V2A
C7220F 210V
QUIESCENT CURRENT = 180A
TRANSITION CURRENT (Burst ModeOPERATION/CONTINUOUS OPERATION) = 450mA
3
11
12
SHUTDOWN
6
C20.1F
+
SGND PGND
PDRIVE
NDRIVE
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Application Note 54
AN54-8
LTC1148: (5V to 3.3V/5A) High EfficiencyStep-Down Converter
Many new microprocessor designs require 3.3V, yet theyare used in systems where 5V is the primary source of
power. A high efficiency 5V to 3.3V converter is drawn inFigure 6A. It supplies up to 5A load using only surfacemount components. Two P-channel MOSFETs are con-nected in parallel to decrease their conduction losses.Efficiency at 5V input is 90%; this means only 1.6W is lost.The lost power is distributed between RSENSE, L1 and thepower MOSFETs, thus no heat sinking is required. OUTPUT CURRENT (A)
EFFICIENCY(%)
100
90
80
700.001 0.1 1 10
AN54 F06B
0.01
Figure 6B. LTC1148: (5V to 3.3V/5A)Buck Converter Measured Efficiency
Figure 6A. LTC1148: (5V to 3.3V/5A) High Efficiency Step-Down Converter
0V = NORMAL>2V = SHUTDOWN
Q1Si9433DY
Q2Si9433DY
+C11F
C20.1F
C70.01F
L15H
R20.02
VOUT3.3V5A
+
VIN5V
C5150pFNPO
C43300pF
R1470 + C6
220F10V3
C333F6.3V2
D1MBRS140T3
AN54 F06A
Q3Si9410DY
ITH
CT
SGND PGND
LTC1148-3.3
VINPDRIVE
SENSE +
SENSE
NDRIVE
SHUTDOWN10
4
1
8
7
14
3
11
12
6
C1 TANTALUM
C3 PANASONIC ECG-COJB330
C6 AVX (Ta) TPSE227K01R0080 ESR = 0.080 IRMS= 1.285A
Q1, Q2 SILICONIX PMOS BVDSS= 12V DCRON= 0.075 Qg= 60nC
Q3 SILICONIX NMOS BVDSS= 30V DCRON= 0.050 Qg= 30nC
D1 MOTOROLA SCHOTTKY VBR = 30V
R2 KRL MP-2A-C1-0R020J Pd = 3W
L1 COILTRONICS CTX02-12483-1
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Application Note 54
LTC1148: (5V to 3.5V/3A) High EfficiencyStep-Down Converter
Some processors require 3.5V or other intermediate volt-age derived from a 5V supply. A good solution for them is
the circuit in Figure 7A. An adjustable version of theLTC1148 allows precise output voltage adjustment, whilepreserving efficiencies of 95%. The output voltage is setby resistors R3 and R4.
OUTPUT CURRENT (A)
0.001
EFFICIENCY(%)
100
95
90
85
80
75
70
65
600.01 0.1
AN54 F07B
1 4
Figure 7B. LTC1148: (5V to 3.5V/3A)Measured Efficiency
Q1Si9433DY
AN54 F07A
C6, 0.01F
C20.1F
VOUT3.5V3A
SHUTDOWN100pF
C6100F 10V3
C322F 25V2
R410k1%
L1
10H
LTC1148
+
C43300pF
X7R
1
2
3
4
5
6
7
14
13
12
11
10
9
8
PDRIVE
NC
VIN
CT
INT VCC
ITH
SENSE
NDRIVE
NC
PGND
SGND
SHUTDOWN
ADJ
SENSE+
C3 AVX (Ta) TPSD226M025R0200 ESR = 0.20 IRMS= 0.866A
C6 AVX (Ta) TPSD107M01R0100 ESR = 0.10 IRMS
= 1.225A
Q1 SILICONIX PMOS BVDSS= 12V DCRON= 0.110 Qg = 20nC
Q2 SILICONIX NMOS BVDSS= 30V DCRON= 0.05 Qg = 30nC
D1 MOTOROLA SCHOTTKY VBR = 30V
R2 KRL SL-C1-1/2-0R033J Pd = 1/2W
L1 COILTRONICS CTX10-4 DCR = 0.038 Kool MCORE
+
R318.2k1%
R20.033
D1MBRS130T3
R1510
Q2Si9410DY
VOUT= 1.25V (1 + R3/R4)
+
VIN5V+
C5180pF
NPO
Figure 7A. LTC1148: (5V to 3.5V/3A) High Efficiency Step-Down Converter
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Application Note 54
AN54-10
LTC1149: (10V-48V to 5V/2A) High VoltageBuck Converter
Previous circuits can accept inputs up to 14V. If higherinput voltage is required the LTC1149 can be used. This IC
is designed for inputs of up to 48V. A basic step-downapplication circuit is shown in Figure 8A. It operates in thesame fashion as the circuit in Figure 1A and provides5V/2A output. However, different MOSFETs are used sincethey must withstand 48V between source and drain. Highcurrent efficiency exceeds 92% over wide range of inputvoltages. Since the control and drive circuitry are powereddirectly from the input line, DC bias current and gatecharge current result in slightly lower efficiency at lightand moderate loads due to high input voltage (relative toLTC1148). This characteristic is eliminated in the circuit ofFigure 11A. A circuit board has been laid out for this circuitand has subsequently been thoroughly tested under full
operating conditions and optimized for mass productionrequirements. A Gerber file for the board is available uponrequest.
OUTPUT CURRENT (A)
0.00150
EFFICIENCY(%)
70
80
90
100
0.01 0.1 2
AN54 F08B
60
1
VIN= 12V
VIN= 48V
VIN= 36V
VIN= 24V
Figure 8B. LTC1149: (10V-48V to 5V/2A) High VoltageBuck Converter Measured Efficiency
AN54 F08A
C2 UNITED CHEMI-CON (Al) LXF63VB331M12.5 x 30 ESR = 0.170IRMS= 1.280A
C4 (Ta)C10 SANYO (OS-CON) 10SA22OM ESR = 0.035 IRMS= 2.360A
Q1 IR PMOS BVDSS= 60V RDSON= 0.280 CRSS = 65pF Qg= 19nC
Q2 IR NMOS BVDSS= 60V RDSON= 0.100 CRSS = 79pF Qg= 28nC
D1 SILICON VBR = 75V
D2 MOTOROLA SCHOTTKY VBR = 60V
R2 KRL NP-1A-C1-0R050J Pd = 1W
L1 COILTRONICS CTX62-2-MP DCR = 0.040MPP CORE
ALL OTHER CAPACITORS ARE CERAMIC
VCC
VCC
CAP
SD1
SD2
ITH
CT
LTC1149-5
PGATE
VIN
SENSE +
SENSE
NGATE
D11N4148
+
C90.01F
+
VIN10V TO 48V C1
0.1F
+C41F
C50.1F
C6
0.068FZ5U
R11k
C73300pFX7R
C8680pFNPO
3
5
16
10
15
7
6
1
4
9
8
13
C30.047F
Z5U
Q1IRFU9024
Q2IRFU024
D2MBR160
C2330F63V
L162H
R20.05
5V
2A
C10220F 210V
QUIESCENT CURRENT = 1.5mA
TRANSITION CURRENT (Burst Mode OPERATION/CONTINUOUS OPERATION) = 570mA
2
11
12
14
SGND PGND
PDRIVE
RGND
Figure 8A. LTC1149: (10V-48V to 5V/2A) High Voltage Buck Converter
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Application Note 54
LTC1149: (10V-48V to 5V/2A) High Voltage BuckConverter with Large P-Channel and N-ChannelMOSFETs
Figure 9A is similar to Figure 8A with much larger MOSFETs
(TO220 package). These transistors have lower RDS(ON)which reduces their I2R losses by roughly a factor of 2.However, the efficiency improves (compared to Figure8B) only at 2A output current with minimum input voltage.Under other conditions higher gate capacitance causesincreased gate charge current leading to higher driverloss. Also for high input voltages (roughly greater than24V), transition losses play a significant part. These lossesare proportional to the reverse transfer capacitance CRSS,maximum output current, and the square of input voltage.Larger CRSSfor the oversized P-channel MOSFET causesan efficiency drop (especially for higher input voltages).
Remember, the best MOSFET selection depends on theparticular application.
Figure 9B. LTC1149: (10V-48V to 5V/2A) Measured Efficiencywith Large P-Channel and N-Channel MOSFETs
OUTPUT CURRENT (A)
0.00150
EFFICIENCY(%)
70
80
90
100
0.01 0.1 2
AN54 F09B
60
1
VIN= 12V
VIN= 48V
VIN= 24V
VIN= 36V
AN54 F09A
C2 UNITED CHEMI-CON (Al) LXF63VB331M12.5 x 30 ESR = 0.170IRMS= 1.280A
C4 (Ta)
C10 SANYO (OS-CON) 10SA220M ESR = 0.035 IRMS= 2.360A
Q1 IR PMOS BVDSS= 60V RDSON= 0.140 CRSS = 100pF Qg= 34nC
Q2 IR NMOS BVDSS= 60V RDSON= 0.050 CRSS = 100pF Qg= 32nC
D1 SILICON VBR = 75V
D2 MOTOROLA SCHOTTKY VBR = 60V
R2 KRL NP-1A-C1-0R050J Pd = 1W
L1 COILTRONICS CTX62-2-MP DCR = 0.040MPP CORE
ALL OTHER CAPACITORS ARE CERAMIC
VCC
VCC
CAP
SD1
SD2
ITH
CT
LTC1149-5
VIN
SENSE +
SENSE
D11N4148
+
C90.01F
+
VIN10V TO 48V
C10.1F
+C41F
R11k
C73300pFX7R
C8680pFNPO
3
5
1610
15
7
6
1
4
9
8
13
C30.047FZ5U
Q1IRF9Z34
Q2IRFZ34
D2MBR160
C2330F63V
L162H
R20.05
5V
2A
C10220F 210V
QUIESCENT CURRENT = 1.5mA
TRANSITION CURRENT (Burst Mode OPERATION/CONTINUOUS OPERATION) = 560mA
2
11
12
14
PGATE
NGATESGND PGND
PDRIVE
RGND
C50.1F
C6
0.068FZ5U
Figure 9A. LTC1149: (10V-48V to 5V/2A) High Voltage Buck Converter with Large P-Channel and N-Channel MOSFETs
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Application Note 54
AN54-12
LTC1149: (10V-48V to 3.3V/2A) High VoltageBuck Converter
If 3.3V has to be generated efficiently from a high voltageinput, use the circuit of Figure 10A. It copies the configu-ration presented in Figure 8A but uses the LTC1149-3.3regulator to provide a precise 3.3V output. In spite ofthe high input and low output voltages, efficiency stillreaches 92%.
OUTPUT CURRENT (A)
0.00150
EFFICIENCY(%)
70
80
90
100
0.01 0.1 2
AN54 F10B
60
1
VIN= 48V
VIN= 12V
VIN= 36V
VIN= 24V
Figure 10B. LTC1149: (10V-48V to 3.3V/2A) High VoltageBuck Converter Measured Efficiency
Figure 10A. LTC1149: (10V-48V to 3.3V/2A) High Voltage Buck Converter
AN54 F10A
C2 UNITED CHEMI-CON (Al) LXF63VB331M12.5 30 ESR = 0.170IRMS= 1.280A
C4 (Ta)
C10 SANYO (OS-CON) 10SA220M ESR = 0.035 IRMS= 2.360A
Q1 IR PMOS BVDSS= 60V RDSON= 0.280 CRSS = 65pF Qg= 19nC
Q2 IR NMOS BVDSS= 60V RDSON= 0.100 CRSS = 79pF Qg= 28nC
D1 SILICON VBR = 75V
D2 MOTOROLA SCHOTTKY VBR = 60V
R2 KRL NP-1A-C1-0R050J Pd = 1WL1 COILTRONICS CTX50-2-MP DCR = 0.032MPP CORE
ALL OTHER CAPACITORS ARE CERAMIC
VCC
VCC
CAP
SD1
SD2
ITH
CT
LTC1149-3.3
VIN
SENSE +
SENSE
D11N4148
+
C90.01F
+
VIN10V TO 48V
C10.1F
+C41F
C50.1F
C60.068F
Z5U
R11k
C73300pFX7R
C8470pFNPO
3
5
16
10
15
7
6
1
4
9
8
13
C30.047FZ5U
Q1IRFU9024
Q2IRFU024
D2MBR160
C2330F63V
L150H
R20.05
3.3V2A
C10220F 10V
QUIESCENT CURRENT = 1.5mATRANSITION CURRENT (Burst Mode OPERATION/CONTINUOUS OPERATION) = 570mA
2
11
12
14
PGATE
NGATE
SGND PGND
PDRIVE
RGND
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Application Note 54
AN54 F11A
C2 UNITED CHEMI-CON (Al) LXF63VB331M12.5 30 ESR = 0.170IRMS= 1.280A
C4 (Ta)
C10 SANYO (OS-CON) 10SA220M ESR = 0.035 IRMS= 2.360A
Q1 IR PMOS BVDSS= 60V RDSON= 0.140 CRSS = 100pF Qg= 34nC
Q2 IR NMOS BVDSS= 60V RDSON= 0.050 CRSS = 100pF Qg= 32nC
D1 SILICON VBR = 75V
D2 MOTOROLA SCHOTTKY VBR = 60V
R2 KRL NP-1A-C1-0R050J Pd = 1W
L1 COILTRONICS CTX62-2-MP DCR = 0.040MPP CORE
ALL OTHER CAPACITORS ARE CERAMIC
VCC
VCC
CAP
SD2
ITH
CT
LTC1149
VIN
SENSE+VFB
SENSE
D11N4148
+
C90.01F
D41N4148
+
VIN10V TO 48V C1
0.1F
+ C41F
R11k
Q32N3904
Q42N3906
33k
10k 33k
D35.1V
432k1%
49.9k1%C7
3300pFX7R
C8200pFNPO
3
5
16
15
7
6
1
4
9
10
8
13
C30.047FZ5U
Q1
IRF9Z34
Q2IRFZ34
D2MBR160
C2330F63V
L162H
R20.05
VOUT12V2A
C10220F 210V
QUIESCENT CURRENT = 1.5mA
TRANSITION CURRENT (Burst Mode OPERATION/CONTINUOUS OPERATION) = 560mA
2
11
12
14
PGATE
NGATESGND PGND
PDRIVE
RGND
C50.1F
C60.068F
Z5U
10k
Figure 11A. LTC1149: (10V-48V to 12V/2A) High Voltage Buck Converter
LTC1149: (10V-48V to 12V/2A) High VoltageBuck Converter
The LTC1149 contains an internal 10V low dropout linearregulator to provide power to the control circuitry. It
actually means that the DC bias current as well as the gatecharge current come directly from the input line, causingslight efficiency degradation, especially for high inputvoltages (additional power is dissipated by the internalregulator). A solution for this problem is presented inFigure 11A. When the output level reaches about 5V, ZenerD3 starts conducting and saturates Q3, which in turnswitches Q4 on. Now VCCpins 3 and 5 are powered directlyfrom the output. Losses caused by DC current and gatecharge current are significantly reduced allowing im-proved efficiency at high input voltage.
The regulator output must be set up for an output voltageless than 14.5V to provide a margin for the LTC1149 pin5 absolute maximum rating of 16V. It should also be
observed that Q4 turns on when the output is less than 10V(the internal regulator output) and stays on or off under allconditions.
Figure 11B. LTC1149: (10V-48V to 5V/2A) MeasuredEfficiency with Large P-Channel and N-ChannelMOSFETs
OUTPUT CURRENT (A)
0.001
EFFICIENCY(%)
100
95
90
85
80
75
70
65
600.01 0.1
AN54 F11B
1 10
VIN= 15V
VIN= 48V
VIN= 36V
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Application Note 54
AN54-14
LTC1149: High Power Buck Converters
Figures 12A and 13A are examples of high power (morethan 100W) converters that use the LT1149. The regula-tors are powered from the full wave rectified output of a16VRMSto 32VRMStransformer. Input capacitance is verybulky, but it has to ensure that ripple valleys do not dipbelow the minimum regulator input requirement. Thecircuit in Figure 13A has additional gate driver circuitswhich are required to improve MOSFET switching times.Overall efficiency goes as high as 98%! Remember, atthese output current levels layout becomes extremelyimportant, and all the recommendations from the LTC1149data sheet must be closely followed.
COUT, 1500F25V, 2
PGATE
VIN
VCC
PDRIVE
VCC
CT
ITH
SENSE
CAP
SD2
RGND
NGATE
PGND
SGND
VFB
SENSE+
SHUTDOWN(NORMALLY GND)
100pF
VIN16VRMS
RECTIFIED
+
+
10F
0.33F
0.33F
R2205k
100
LTC1149
100
3300pFCT
270pF
470
RS0.0082
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
Q1RFG60P06E
Q2IRFZ44
D2MBR380
D11N4148
AN54 F12A
OUTPUTGROUNDCONNECTION
L33H
1.5F63VWIMA
1FWIMA
33k
VOUT13.8V10A
1000pF
COUTPANASONIC HFQ SERIESD2 MOTOROLA SCHOTTKYQ1 HARRIS PMOS BV DSS= 60V RDSON= 0.03
0.22F CIN
20000F35V
+
R120.5k1%
Figure 12A. LTC1149: (16VRMSto 13.8V/10A) Buck Converter
OUTPUT CURRENT (A)
0.01
EFFICIENC
Y(%)
100
95
90
85
80
75
70
650.1 1 10
AN54 F12B
Figure 12B. LTC1149: (16VRMSto 13.8V/10A)Buck Converter Measured Efficiency
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Application Note 54
COUT, 1000F35V
PGATE
VIN
VCC
PDRIVE
VCC
CT
ITH
SENSE
CAP
SD2
RGND
NGATE
PGND
SGND
VFB
SENSE+
SHUTDOWN(NORMALLY GND)
100pF
VIN32VRMS
RECTIFIED
+
+
10F
0.33F
MPSW06
MPSA56
PDRIVE
BUFFER
NDRIVE
BUFFER
0.33F
R2432k
100
LTC1149
100
3300pFCT
150pF
470
RS0.016
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
Q1SMP40P06
Q2IRFZ34
D2MBR380
AN54 F13A
OUTPUTGROUNDCONNECTION
L62H
1N4148
D11N4148
1.5F63VWIMA
1FWIMA
33k
VOUT27.6V5A
1000pF
0.22F
CIN
5000F75V
+
R120.5k1%
MPSA56
COUTPANASONIC HFQ SERIESD2 MOTOROLA SCHOTTKYQ1 SILICONIX PMOS BV DSS= 60V RDSON= 0.045
Figure 13A. LTC1149: (32VRMSto 27.6V/5A) Buck Converter
OUTPUT CURRENT (A)
0.01
EFFICIENCY(%)
100
95
90
85
80
75
70
650.1 1 10
AN54 F13B
Figure 13B. LTC1149: (32VRMSto 27.6V/5A) Buck Converter Measured Efficiency
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Application Note 54
AN54-16
LTC1147: (5V-14V to 5V/1A) Buck Converter withSurface Mount Technology
The LTC1147 (Figure 14A) is a great way to implement ahigh efficiency regulator using a minimum number ofexternal components and occupying the least board space.This regulator provides many advantages of the LTC1148including constant off-time configuration, low dropoutregulation and Bust Mode operation, comes in a smallerpackage and does not require the N-channel MOSFET. Theonly sacrifice made is synchronous rectification whichdegrades the efficiency of this circuit up to three percent-age points. Compare efficiency graphs in Figures 1B and14B! Since the clamp diode D1 conducts all the timeduring the off-time, a larger diode (MBRD330) is used forthis circuit. The LTC1147 is an excellent choice where theoutput current is less than 1A, and where the input voltageis less than twice the output voltage.
Figure 14B. LTC1147: (5V-14V to 5V/1A)Buck Converter Measured Efficiency
OUTPUT CURRENT (A)
0.00150
EFFICIENC
Y(%)
70
80
90
100
0.01 0.1 1
AN54 F14B
60
VIN= 6V
VIN= 10V
VIN= 14V
AN54 F14A
C2 AVX (Ta) TPSD226K025R0200 ESR = 0.200 IRMS= 0.775AC5 AVX (Ta) TPSE227K010R0080 ESR = 0.080 IRMS= 1.285AQ1 SILICONIX PMOS BVDSS= 20V RDSON= 0.100 CRSS = 400pF Qg= 50nCD1 MOTOROLA SCHOTTKY VBR = 30V
R2 KRL SP-1/2-A1-0R100J Pd = 0.75W
L1 COILTRONICS CTX100-4 DCR = 0.175Kool MCORE
ALL OTHER CAPACITORS ARE CERAMIC
ITH
CT
GND
LTC1147-5
VIN
SENSE +
SENSE
+
C50.001F
+
VIN5V TO 14V
R11k
C33300pFX7R
C4390pFNPO
2
8
5
4
Q1Si9430DY
D1MBRD330
C222F x 225V
100H
R20.1
5V
1A
C6220F 10V
QUIESCENT CURRENT = 190ATRANSITION CURRENT (Burst ModeOPERATION/
CONTINUOUS OPERATION) = 170mA
1
7
SHUTDOWN6
+
L1
1
2
4
3
C10.1F
3
PDRIVE
Figure 14A. LTC1147: (5V-14V to 5V/1A) Buck Converter with Surface Mount Technology
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Application Note 54
OUTPUT CURRENT (A)
0.00150
EFFICIENCY(%)
70
80
90
100
0.01 0.1 1
AN54 F15B
60
VIN= 5V
VIN= 10V
VIN= 14V
Figure 15B. LTC1147: (4V-14V to 3.3V/1A)Buck Converter Measured Efficiency
LTC1147: (4V-14V to 3.3V/1A) Buck Converter withSurface Mount Technology
Figure 15A shows another compact circuit with theLTC1147 series. It generates 3.3V/1A output using thesame configuration as in the previous example. Despitethe lack of synchronous rectification, efficiency approaches95% with 5V input.
AN54 F15A
C2 AVX (Ta) TPSD226K025R0200 ESR = 0.200 IRMS= 0.775AC6 AVX (Ta) TPSE227K010R0080 ESR = 0.080 IRMS= 1.285AQ1 SILICONIX BVDSS= 20V DCRON= 0.100 CRSS = 400pF Qg= 50nCD1 MOTOROLA
R2 KRL SP-1/2-A1-0R100 Pd = 0.75W
L1 COILTRONICS CTX100-4 DCR = 0.175Kool MCORE
ITH
CT
GND
LTC1147-3.3
VINPDRIVE
SENSE +
SENSE
+
C50.001F
+
VIN4V TO 14V
R11k
C33300pFX7R
C4560pFNPO
2
8
5
4
Q1Si9430DY
D1MBRD330
C222F 225V
100H
R20.1
3.3V1A
C6220F 10V
QUIESCENT CURRENT = 170ATRANSITION CURRENT (Burst Mode OPERATION/CONTINUOUS OPERATION) = 170mA
1
7
SHUTDOWN6
+
L1
1
2
4
3
C10.1F
3
Figure 15A. LTC1147: (4V-14V to 3.3V/1A) Buck Converter with Surface Mount Technology
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Application Note 54
AN54-18
LTC1147: (4V-8V to 3.3V/1.5A) Buck Converter withSurface Mount Technology
One more application circuit with LTC1147 is presented inFigure 16A. It is optimized for 5V to 3.3V conversion with
input voltages of 4V to 8V (limited by the P-channelMOSFET). A circuit board has been laid out for this circuitand has subsequently been thoroughly tested under fulloperating conditions and optimized for mass productionrequirements. A Gerber file for the board is available uponrequest.
AN54 F16A
C1 AVX TPSD476M016R0150 TANTALUM 47F 16V
C6 AVX TPSD107M010R0100 TANTALUM 100F 10V
D1 MOTOROLA MBRS130LT3 BVR = 30V
L1 SUMIDA CDR74B-100LC 10 H
Q1 SILICONIX PMOS Si9433
R2 IRC LRC-LR2010-01-R068-F
ALL OTHER CAPACITORS CERAMIC
ITH
CT
GND
LTC1147-3.3
VINPDRIVE
SENSE +
SENSE
+
C5
0.01F+
VIN4V TO 8V
0V = NORMAL
2V = SHUTDOWN
R11k
C33300pF
C4120pF
2
8
5
4
D1MBRS130LT3
C147F16V
R20.068
VOUT3.3V1.5A
C6100F 10V
1
7
SHUTDOWN6
L1
10H
C20.1F
3
Q1P-CH
Si9433DY
Figure 16A. LTC1147: (4V-8V to 3.3V/1.5A) Buck Converter with Surface Mount Technology
OUTPUT CURRENT (A)
0.001
EFFICIEN
CY(%)
100
95
90
85
80
75
70
65
600.01 0.1 1
AN54 F16B
LTC1147-3.3SUMIDA CDR74B
VIN= 5V
LTC1147-3.3SUMIDA CD54
VIN
= 5V
2
Figure 16B. LTC1147: (4V-8V to 3.3/1.5A)Buck Converter Measured Efficiency
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Application Note 54
LTC1148: (10V-14V to 5V/10A) High CurrentBuck Converter
Due to differences in physical structure between N- and P-channel MOSFETs, the former are usually more cost
effective, more available, and provide better internal pa-rameters for the same size. This is especially importantwhen high output currents are required. With 5A to 10Aoutput currents the use of N-channel MOSFETs in place ofP-channel is the most preferable solution. An implemen-tation of this idea is presented in Figure 17A.
A special Q4 gate drive circuit that uses a bootstrappingtechnique is added to provide required gate drive. Whenpin 1 goes high it turns Q3 on, providing a path for fast Q4gate capacitance discharge. With Q3 off, Q1 and Q2
saturate each other feeding positive voltage to Q4s gate.As a result Q4 turns on, and the positive pulse at its sourceis AC coupled through C6 supplying bootstrapped VCCforthe gate drive SCR. The external driver circuit contains
only inexpensive, readily available small-signal transis-tors, yet allows the use of all N-channel MOSFETs. Effi-ciency reaches 96% (see Figure 17B).
OUTPUT CURRENT (A)
0.150
EFFICIENCY(%)
70
80
90
100
1 10
AN54 F17B
60
VIN= 10V
VIN= 14V
Figure 17A. LTC1148: (10V-14V to 5V/10A) High Current Buck Converter
Figure 17B. LTC1148: (10V-14V to 5V/10A) High CurrentBuck Converter Measured Efficiency
Q4IRFZ44
AN54 F17A
C1 (Ta)
C7 UNITED CHEMI-CON (Al) LXF35VB272M16 X 40 ESR = 0.018 IRMS= 2.900AC8 NICHICON (Al) UPL1C222MRH ESR = 0.028 IRMS= 2.010AQ4, Q5 IR NMOS BVDSS= 60V DCRON= 0.028 CRSS = 310pF Qg= 69nCD1, D2 MOTOROLA SILICON VBR = 75V
D3 MOTOROLA SCHOTTKY VBR = 30V
ITH
CT
SGND PGND
LTC1148-5
VINPDRIVE
SENSE +
SENSE
NDRIVE
C50.001F
+
VIN10V TO 14V
C1
1F
R41k
C3
3300pFX7R
C4820pFNPO
10
4
1
8
7
14
Q5IRFZ44
D31N5818
C6
0.47F
R80.01
5V10A
C82200F 3 16V
3
11
12
SHUTDOWN
6
C2
0.1F
+
Q3VN2222LL
D11N4148
R120k
Q12N3906
Q22N2222
+ C72700F 235V
R6100
D21N4148
R3220
L1
33H
R722k
R2220
R5100
R8 KRL NP-2A-C1-0R010J Pd = 3W
L1 COILTRONICS CTX33-10-KM DCR = 0.010Kool MCORE
ALL OTHER CAPACITORS ARE CERAMIC
QUIESCENT CURRENT = 22mA
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Application Note 54
AN54-20
Two resistors are placed in series with the current sensepins. This significantly improves circuit noise immunitywhich is of great importance when switching high current.R7, connected between pin 7 and ground, disables Burst
Mode operation so that the regulator operates continuously.
LTC1149: (12V-36V to 5V/5A) High Current, HighVoltage Buck Converter
Figure 18A shows a high current, high voltage buckconverter. The LTC1149 is used to accommodate the inputvoltage requirement. As in Figure 17A the top N-channelMOSFET is driven by an external circuit which inverts thechips P-drive output and uses bootstrapping to providepositive gate-source voltage. The peak-to-peak gate volt-age is defined by the DC portion of the gate driver V CC.
Therefore, not to exceed maximum gate voltage for theMOSFET, D1s anode is connected to internal 10V regula-tor output. In this application PDRIVEpin 4 is used because
an output referenced to ground is required. PGATEpin 1provides the same drive signal referenced to VCC.
Figure 18B. LTC1149: (12V-36V to 5V/5A) High Current, HighVoltage Buck Converter Measured Efficiency
OUTPUT CURRENT (A)
0.150
EFFICIENCY(%)
70
80
90
100
1 5
AN54 F18B
60
VIN= 12V
VIN= 24V
VIN= 36V
Figure 18A. LTC1149: (12V-36V to 5V/5A) High Current, High Voltage Buck Converter
Q4MTP30N06EL
AN54 F18A
C60.001F
+
C70.22F
R70.02
5V5A
C9220F 2 10V
Q3VN2222LL
D11N4148
R210k
Q12N3906
Q2
2N2222
C81000F 63V
D21N4148
R4220
L1
50H
R3220
VCC
VCC
CAP
SD1
SD2
ITH
CT
LTC1149-5
PGATE
VIN
SENSE +
SENSE
NGATE
VIN12V TO 36V
C10.1F
+C21F
C30.1F
R11k
C43300pF
X7R
C5820pFNPO
3
5
16
10
15
7
6
4
9
8
13
2
11
12
14
SGND PGND
PDRIVE
RGND
Q5IRFZ34
D3MBR160
C2 (Ta)
C8 NICHICON (Al) UPL1J102MRH ESR = 0.027 IRMS= 2.370A
C9 SANYO (OS-CON) 10SA220M ESR = 0.035 IRMS= 2.360A
Q1 PNP BV CEO= 30V
Q2 NPN BVCEO= 40V
Q3 SILICONIX NMOS BVDSS= 60V RDSON= 5.000
Q4 MOTOROLA NMOS BVDSS= 60V RDSON= 0.050 CRSS = 100pF Qg= 40nC
R6100
R5100
+
1
Q5 IR NMOS BVDSS= 60V RDSON= 0.050 CRSS = 100pF Qg= 32nC
D1, D2 SILICON VBR = 75V
D3 MOTOROLA SCHOTTKY VBR = 60V
R7 KRL NP-2A-C1-0R020J Pd = 3W
L1 COILTRONICS CTX50-5-52 DCR = 0.021 #52 IRON POWDER CORE
ALL OTHER CAPACITORS ARE CERAMIC
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Application Note 54
LTC1149: (12V-48V to 5V/10A) High Current, HighVoltage Buck Converter
The circuit in Figure 19A uses the same configuration butis designed to provide up to 10A output current. Besidesthe usual external component changes, the circuit useshigher current MOSFETs to improve efficiency at maxi-mum power levels. Efficiency at 5A output is severalpercentage points better than in the previous example(compare Figures 18B and 19B). R7 keeps the regulator incontinuous mode causing the rapid efficiency decrease atlighter loads.
Figure 19B. LTC1149: (12V-48V to 5V/10A) High Current,High Voltage Buck Converter Measured Efficiency
OUTPUT CURRENT (A)
0.150
EFFICIENCY(%)
70
80
90
100
1 10
AN54 F19B
60
VIN= 12V
VIN= 48V
VIN= 36V
VIN= 24V
Q4IRFZ34
AN54 F19A
C60.001F
+
C70.22F
R80.01
5V10A
Q3VN2222LL
D11N4148
R220k
Q12N3906
Q22N2222
C81000F 2 63V
D21N4148
R4220
L1
33H
R3220
VCC
VCC
CAP
SD1
SD2
ITH
CT
LTC1149-5
PGATE
VIN
SENSE +
SENSE
NGATE
VIN12V TO
48V
C10.1F
+C21F
C30.1F
R11k
C43300pF
X7R
C5820pFNPO
3
5
16
10
15
7
6
1
4
9
8
13
2
11
12
14
SGND PGND
PDRIVE
RGND
Q5IRFZ44
D3MBR160
C2 (Ta)
C8 NICHICON (Al) UPL1J102MRH ESR = 0.027 IRMS= 2.370A
C9 NICHICON (Al) UPL1C222MRH ESR = 0.028 IRMS= 2.010A
Q1 PNP BVCEO= 30V
Q2 NPN BVCEO= 40V
Q3 SILICONIX NMOS BVDSS= 60V RDSON= 5.000
Q4 IR NMOS BVDSS= 60V RDSON= 0.050 CRSS = 100pF Qg= 32nC
Q5 IR NMOS BVDSS= 60V RDSON= 0.028 CRSS = 310pF Qg= 69nC
R6100
R5100
+
R722k
QUIESCENT CURRENT = 26mA
+
C9220F 3 16V
D1, D2 SILICON VBR = 75V
D3 MOTOROLA SCHOTTKY VBR = 60V
R8 KRL NP-2A-C1-0R010J Pd = 3W
L1 COILTRONICS CTX33-10-KM DCR = 0.010Kool MCORE
ALL OTHER CAPACITORS ARE CERAMIC
Figure 19A. LTC1149: (12V-48V to 5V/10A) High Current, High Voltage Buck Converter
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Application Note 54
AN54-22
Figure 20A. LTC1149: (32V-48V to 24V/10A) High Current, High Voltage Buck Converter
9
8
Q4
IRFZ44
AN54 F20A
C70.001F
C70.22F
24V10A
C101000F 3 35V
Q3VN2222LL
D1IN4148
R320k
Q12N5087
Q2MPS651
C81000F 2 63V
D21N4148
R25.1k
L1
50H
VCC
VCC
CAP
SD2
ITH
CT
LTC1149
PGATE
VIN
VFB
SENSE +
NGATE
VIN32V TO 48V
C10.1F
+ C21F
C30.1F
R11k
C43300pF
X7R
C5270pFNPO
3
5
16
15
7
6
4
10
13
2
11
12
14
SGND PGND
PDRIVE
RGND
Q5IRFZ44
C2 (Ta)C9 NICHICON (Al) UPL1J102MRH ESR = 0.027 IRMS= 2.370A
C10 NICHICON (Al) UPL1V102MRH ESR = 0.029 IRMS= 1.980A
Q4, Q5 IR NMOS BVDSS= 60V RDSON= 0.028 CRSS = 310pF Qg= 69nC
Q1 PNP BVCEO= 50V
Q2 NPN BVCEO= 60V
D1, D2, D3, D4 SILICON VBR = 75V
D5 MOTOROLA SCHOTTKY VBR = 60V
R10 KRL NP-2A-C1-0R010J Pd = 3W
L1 COILTRONICS CTX50-10-KM DCR = 0.010Kool MCORE
ALL OTHER CAPACITORS ARE CERAMIC
100
R6100
+
SENSE
1
C6100pF
R8220k1%
R5220
D31N4148
R4220
D41N4148
R912k1%
D5MBR160
R100.01
R7
VOUT= 1.25V (1 + R8/R9)
QUIESCENT CURRENT = 26mA
TRANSITION CURRENT (Burst Mode OPERATION/CONTINUOUS OPERATION) = 1.5A
+
+
R1139k
LTC1149: (32V-48V to 24V/10A) High Current, HighVoltage Buck Converter
If an output voltage other than 5V or 3.3V is required, anadjustable version of the regulator must be used. A 24V/10A example is shown in Figure 20A. The output voltageis set by resistors R8 and R9. The LTC1149 monitors VFB(pin 10) keeping it at 1.25V. Similar to the previous twocircuits, an external gate driver is added to switch theN-channel MOSFET Q2. To ensure consistent start-up ofthe bootstrapping circuitry, the driver is initially poweredby R2 and D2. (The main requirement at start-up is tosupply the driver with VCC that exceeds output targetvoltage.) After the switching starts, D1 an D3 power theexternal gate drive circuit.
OUTPUT CURRENT (mA)
1050
EFFICIEN
CY(%)
70
80
90
100
100 1A 10A
AN54 F20B
60
VIN= 32V
VIN= 45V
Figure 20B. LTC1149: (32V-48V to 24V/10A) High Current,High Voltage Buck Converter Measured Efficiency
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Application Note 54
LT1148: (4V-14V to 5V/1A) SEPIC Converter
Figure 21A provides the function of a step-up and step-down converter without using a transformer. This topol-ogy is called a SEPIC converter. The P-channel transistorand L1 are arranged similarly to a buck-boost topologyproviding the boost part of the regulator. Pulses at Q2sdrain (actually two paralleled devices) are coupled via C8to the buck portion that includes Q3 and L2. This circuitaccepts 4V to 14V input and provides a solid 5V output.Even though the schematic shows two inductors, theycarry the same current and can be wound on a single core.Such dual coils are readily available (see circuit parts list).This topology is acceptable for moderate loads only, as thecoupling capacitor C8 carries the full load current and
must be sized accordingly. When the sense resistor isplaced at ground potential, such as the case in this circuit,the off-time increases approximately 40%.
An adjustable version of the regulator is required when the
OUTPUT CURRENT (A)0.001
50
EFFICIENCY(%)
70
80
90
100
0.01 0.1 1
AN54 F21B
60
VIN= 14V
VIN= 4V
VIN= 5V
VIN= 4V
VIN= 10V
VIN= 5V
current sense resistor is placed at ground. This allows toprovide different output voltages. D2 is included for foldbackshort-circuit protection. When VOUTequals zero (output isshorted) D2 clamps pin 6 and limits the output current.
Figure 21B. LTC1148: (4V-14V to 5V/1A)Buck-Boost Converter Measured Efficiency
Figure 21A. LTC1148: (4V-14V to 5V/1A) SEPIC Converter
AN54 F21A
C60.1F
VOUT5V
1A
C10220F 10V
Q2Si9430DY x 2
C7100F20V
VIN4V TO14V C1
1F
C20.1F
R11k
C43300pF
X7R
C5390pFNPO
5
10
6
4
1
9
8
7
D2MBR0520L
14
3
11
12
D11N5818
C1 (Ta)
C7 SANYO (OS-CON) 20SA100M ESR = 0.037 IRMS= 2.250A
C8, C10 SANYO (OS-CON) 10SA220M ESR = 0.035 IRMS= 2.360A
Q2 SILICONIX PMOS BVDSS= 20V RDSON= 0.100 CRSS = 400pF Qg= 50nC
Q3 SILICONIX NMOS BVDSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 30nC
D1 MOTOROLA SCHOTTKY VBR = 30V
R2 KRL NP-1A-C1-0R082J Pd = 1W
L1 COILTRONICS CTX50-4P, CTX50-5P
ALL OTHER CAPACITORS ARE CERAMIC
+
R20.082
TO VOUT
SHUTDOWN
ITH
CT
LTC1148
PDRIVE
VIN
SENSE +
NDRIVESGND PGND
VFB
SENSE
INT VCC
C8220F10V
L150H
Q3Si9410DY
R375k1%
R425k1%
+
C9100pF
++
L250H
VOUT= 1.25V (1 + R3/R4)
QUIESCENT CURRENT = 200A
TRANSITION CURRENT (Burst Mode OPERATION/
CONTINUOUS OPERATION) = 250mA/VIN= 5V
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Application Note 54
AN54-24
OUTPUT CURRENT (A)
0.00150
EFFICIEN
CY(%)
70
80
90
100
0.01 0.1 0.5
AN54 F22B
60
VIN= 14VVIN= 4V
VIN= 10VVIN= 5V
LTC1148: (4V-14V to 5V/0.5A, 5V/0.5A)Split Supply Converter
Applications requiring a split supply can use the circuitpresented in Figure 22A. It contains the converter from
Figure 21A and adds a synchronous charge pump Q4 toprovide a 5V output. Q4 source is referenced to the 5Vline, and its gate drive is AC coupled via C11 and clampedby D3. The outputs exhibit excellent tracking with line andload changes. This is a great way to build a dual outputconverter without any transformer.
SENSE
AN54 F22A
C70.1F
C10220F 10V
Q2Si9430DY
C8100F20V
VIN4V TO14V C1
1F
C20.1F
R11k
C43300pF
X7R
C5390pFNPO
5
10
6
4
1
8
7
9
14
3
11
12
D11N5818
C1 (Ta)
C8 SANYO (OS-CON) 20SA100M ESR = 0.037 IRMS= 2.250AC9, C10, C12 SANYO (OS-CON) 10SA220M ESR = 0.035 IRMS= 2.360AQ2 SILICONIX PMOS BVDSS= 20V RDSON= 0.100 CRSS = 400pF Qg= 50nCQ3, Q4 SILICONIX NMOS BVDSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 30nCD1, D2 MOTOROLA SCHOTTKY VBR = 30V
R2 KRL NP-1A-C1-0R082J Pd = 1W
L1 COILTRONICS CTX50-4
+
R20.05
VOUT
SHUTDOWN
ITH
CT
LTC1148
PDRIVE
VIN
SENSE +
NDRIVESGND PGND
VFB
INT VCC
C9220F10V
L150H
Q3Si9410DY
R375k1%
R425k1%
C110.22F
++
L250H
VOUT= 1.25V (1 + R3/R4)
QUIESCENT CURRENT = 250A TRANSITION CURRENT (DIS/CONT) = 130mA/VIN= 5V
C6100pF
R551k
D31N4148
C12220F 10V
VOUT5V0.5A
+VOUT5V0.5A
+
+
Q4Si9410DY
D2
1N5818
D4MBR0520L
Figure 22A. LTC1148: (4V-14V to 5V/0.5A, 5V/0.5A) Split Supply Converter
Figure 22B. LTC1148: (4V-14V to 5V/0.5A, 5V/0.5A)Split Supply Converter Measured Efficiency
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Application Note 54
LTC1148: (4V-10V to 5V/1A) Positive-to-NegativeConverter
Figure 23A shows a buck-boost converter using theLTC1148. This is an inverting topology, and it can inher-ently buck or boost the input voltage. Ground pins of thechip are referenced to the output line; no additional levelshifting circuit is required to drive the N-channel FET Q3(its source is referenced to 5V as well). Now even withminimum input level, the circuit provides a solid 9V peak-to-peak MOSFET drive signal. However, so as not toexceed absolute maximum voltage at pin 3, the input lineis limited to 10V. If the circuit is required to accept a higherinput voltage, the LTC1148HV can be used instead. Q1 isadded to provide a logic level shutdown feature. If shut-down is not needed omit Q1 and R1, and short pin 10 topin 11.
Figure 23A. LTC1148: (4V-10V to 5V/1A) Positive-to-Negative Converter
OUTPUT CURRENT (A)
0.001
EFFICIEN
CY(%)
100
95
90
85
80
75
70
65
600.01 0.1
AN54 F23B
1 10
4V TO 5V/1A
10V TO 5V/1A
Figure 23B. LTC1148: (4V-10V to 5V/1A)Positive-to-Negative Converter MeasuredEfficiency
SENSE
AN54 F23A
C50.01F
C8220F 210V
Q2Si9430DY
C7150F 216V
VIN4V TO10V
C11F
C20.1F
R21k
C36800pF
X7R
C4560pFNPO
5
10
6
4
1
8
7
914
3
11
12
D11N5818
C1 (Ta)
C7 SANYO (OS-CON) 16SA150M ESR = 0.035 IRMS= 2.280AC8 SANYO (OS-CON) 10SA220M ESR = 0.035 IRMS= 2.360AQ2 SILICONIX PMOS BVDSS= 20V RDSON= 0.100 CRSS = 400pF Qg= 50nCQ3 SILICONIX NMOS BVDSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 30nCD1 MOTOROLA SCHOTTKY VBR = 30V
R2 KRL NP-1A-C1-0R050J
L1 COILTRONICS CTX50-2-MP DCR = 0.032MPP CORE
ALL OTHER CAPACITORS ARE CERAMIC
+
R20.05
Q1TP0610L
SHUTDOWN
ITH
CT
LTC1148
PDRIVE
VIN
SENSE +
NDRIVESGND PGND
VFB
INT VCC
L150H
Q3Si9410DY
R375k1%
R425k1%
+
VOUT= 1.25V (1 + R3/R4)
C6200pF
5V1A
+R11M
SHUTDOWN
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Application Note 54
AN54-26
LTC1148: (5V-12V to 15V/0.5A) Buck-BoostConverter
Figure 24A presents an inverting regulator designed toaccommodate higher output voltages. The LTC1148 can-
not accept feedback directly from a negative output. Toregulate negative outputs, the feedback must be invertedand compared against 1.25V. This function is provided bya DC level shifting amplifier consisting of Q1 and associ-ated components. Resistor R4 provides amplifier negativefeedback, effectively cancelling variations in VCC, and Q2provides temperature compensation. The output voltageis set by resistors R4 and R5. As usual, with the senseresistor at ground potential, the off-time increases roughlyby 40%.
OUTPUT CURRENT (A)
0.001
EFFICIENCY(%)
95
90
85
80
75
70
650.01 0.1 1
AN54 F24B
5V TO 15V/0.5A
12V TO 15V/0.5A
Figure 24B. LTC1148: (5V-12V to 15V/0.5A)Buck-Boost Converter Measured Efficiency
AN54 F24A
C80.01F
C947F25V
Q3Si9435DY2
C7220F10V
C6200pF
C56800pF
10
6
4
11
1
8
7
9
12
3
U1
D3MBR735
R7 DALE LVR-3 0.033WL1 COILTRONICS CTX50-5-52C7 SANYO OS-CON 105A220KC9, C10 SANYO OS-CON 255C47K
+
R70.033
Q22N5210
Q12N5210
LTC1148
VIN
SHUTDOWN
ITH
CT
SGND
PDRIVE
SENSE+
SENSE
VFB
PGND
L150H
R449.9k1%
+
+ C1047F25V
C20.1F
C31F
C11200pF
R61k
R356k
> 1.5V = SHUTDOWN
R5634k1%
VOUT15V0.5A
VIN5V TO 12V
+
Figure 24A. LTC1148: (5V-12V to 15V/0.5A) Buck-Boost Converter
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Application Note 54
LTC1148: (2V-5V to 5V/1A) Boost Converter
Even though the LTC1148 is mainly used in step-downconverters, it can also show excellent performance in theboost configuration. A boost implementation is shown in
Figure 25A. This is a two-cell to 5V converter that uses theLT1109 to provide 12V to power the main regulator chip(unfortunately, MOSFETs do not operate with only 2V at thegate). The LT1109 is a small micropower IC that requiresonly three external components and provides great effi-ciency. An N-channel transistor is used as the switch, andgeneral purpose MOSFETs Q1 and Q2 are used to form aninverting gate driver. When Q3 turns off, the voltage at itsdrain rises above VIN, and a Schottky diode D2 startsconducting. In a short period of time Q4 shorts it outproviding a synchronous rectification feature and increas-ing efficiency. If 12V is already available, the LT1109 can beomitted and the 12V line connected directly to pin 3.
Figure 25A. LTC1148: (2V-5V to 5V/1A) Boost Converter
Q1TP0610L
SENSE
AN54 F25A
C60.001F
C8220F 210V
VIN2V TO5V
C1100F10V
R21k
C46800pF
X7R
C5390pFNPO
10
6
4
1
12V
8
7
9
14
3
11
12
D21N5818
C1 SANYO (OS-CON) 10SA100M ESR = 0.045 IRMS= 1.870AC3 (Ta)
C8 SANYO (OS-CON) 10SA220M ESR = 0.035 IRMS= 2.360AQ3, Q4 SILICONIX NMOS BVDSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 30nCD1, D2 MOTOROLA SCHOTTKY VBR = 30V
SHUTDOWN
ITH
CT
LT1109
PDRIVE
VIN
SENSE +
NDRIVESGND PGND
VFB
L133H
Q2VN2222LL
R375k1%
+
C7100pF
5V1A
R10.05
VIN
SENSE
GND
S/D7
3
1
4
8
D11N5818
SHUTDOWN
C20.1F
C31F
+
Q3Si9410
L225H
R425k1%
Q4Si9410
+
SW
LTC1148
VR1
R2 KRL SL-1-C1-0R050J Pd = 1W
L1 COILTRONICS CTX33-1 DCR = 0.220Kool MCOREL2 COILTRONICS CTX25-4
VOUT= 1.25V (1 + R3/R4)
Figure 25B. LTC1148: (2V-5V to 5V/1A)Boost Converter Measured Efficiency
OUTPUT CURRENT (A)
0.001
EFFICIENC
Y(%)
100
95
90
85
80
75
70
650.01 0.1 1
AN54 F25B
4V TO 5V/1A
2V TO 5V/1A
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Application Note 54
AN54-28
LTC1143: (5.2V-14V to 3.3V/2A and 5V/2A)Dual Buck Converter
A circuit that provides dual 3.3V/5V output is shown inFigure 26A. It uses a dual LTC1143 regulator that com-
bines two LTC1147, non-synchronous switching regula-tors. The efficiency was measured with only one outputloaded which provided worse results for low output cur-rent due to the presence of the second halfs quiescentcurrent. This circuit provides very simple means to powerdual voltage logic. It occupies small amount of boardspace and is very efficient! OUTPUT CURRENT (A)
0.001
EFFICIENC
Y(%)
95
90
85
80
75
70
65
600.01 0.1
AN54 F26B
1 10
14V TO 3.3V
8V TO 5V
8V TO 3.3V
14V TO 5V
Figure 26B. LTC1143: (5.2V-14V to 3.3V/2A and 5V/2A)Dual Buck Converter Measured Efficiency
+
+ +
PDRIVE3
SENSE+ 3
SENSE 3
GND3 GND5CT3 ITH3 ITH5 CT5
SENSE 5
SENSE+ 5
PDRIVE5
VIN3 SHUTDOWN 5 VIN5
LTC1143
CT5200pF
CT3390pF
3 14 15 7 6 11
RC51k
CC33300pF
CC53300pF
RC31k
13 10 5
12
9
8
4
1
16
VOUT55V/2A
COUT5220F10V 2
RSENSE50.05
L220H
D2MBRD330
RSENSE: KRL SL-1R050J L1, L2: COILTRONICS CTX20-4
CIN3,CIN5: AVX (Ta) TPSD226K025R0200
COUT3,COUT5: AVX (Ta) TPSE227K010R0080Q1, Q2: SILICONIX PMOS Si9430DY
D1MBRD330
0V = NORMAL>1.5V = SHUTDOWN
CIN522F25V 2
CIN322F25V 2 Q1
P-CHSi9430DY
COUT3220F10V2
L120H
RSENSE30.05VOUT3
3.3V/2A
VIN5.2V TO 14V
+
Q2P-CH
Si9430DY
0.01F 0.01F
AN54 F26A
0.22F0.22F
SHUTDOWN 3
2
Figure 26A. LTC1143: (5.2V-14V to 3.3V/2A and 5V/2A) Dual Buck Converter
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Application Note 54
Figure 27B. LTC1148HV-5: (5.2V-18V to 5V/1A) HighVoltage Buck Converter Measured Efficiency
LTC1148HV-5: (5.2V-18V to 5V/1A) High VoltageBuck Converter
The standard LTC1148 input voltage is limited to 16Vabsolute maximum level, which is not sufficient in some
applications. Figure 27A shows a step-down regulatorusing the high voltage LTC1148HV. It contains the sameinternal functions but accepts up to 20V input (remember,MOSFETs gates are usually rated at 20V maximum). As abuilding block it can be used in the same manner asLTC1148. Input tantalum capacitors now have to be ratedat 35V to ensure reliable operation under maximum inputvoltage.
OUTPUT CURRENT (A)
0.001
EFFICIENCY(%)
100
95
90
85
80
75
70
65
60
550.01 0.1 1
AN54 F27B
7V TO 5V
12V TO 5V
18V TO 5V
1
2
3
4
5
6
7
14
13
12
11
10
9
8
PDRIVE
NC
VIN
CT
INT VCC
ITH
SENSE
NDRIVE
NC
PGND
SGND
SHUTDOWN
NC
SENSE+
LTC1148HV-5
+ 1F
1000pFR10.1
SHUTDOWN
L150H
Q2, Si9410DY
D1MBRS140T3
Q1Si9430DY
+ CIN10F35V2
VIN5.2V TO 18V
+
COUT220F10VAVX
VOUT5V/1A
CC3300pF
RC1k
CT220pF
CINCOUTL1
R1Q1Q2
AVX (Ta) TPSD106K035R0300AVX (Ta) TPSE227K010R0080COILTRONICS CTX50-4
KRL SP-1/2-A1-0R100SILICONIX PMOS Si9430DYSILICONIX NMOS Si9410DY
AN54 F27A
Figure 27A. LTC1148HV-5: (5.2V-18V to 5V/1A) High Voltage Buck Converter
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Application Note 54
AN54-30
OUTPUT CURRENT (A)
0.001
EFFICIENCY(%)
100
95
90
85
80
75
70
65
600.01 0.1 1
AN54 F28B
18V to 3.3V
4V to 3.3V
12V to 3.3V
Figure 28B. LTC1148HV-3.3: (4V-18V TO 3.3V/1A)High Voltage Buck Converter Measured Efficiency
LTC1148HV-3.3 (4V-18V to 3.3V/1A) High VoltageBuck Converter
Figure 28A: Here is a high voltage version of the circuitshown in Figure 4A with input voltage increased to 18V.
1
2
3
4
5
6
7
14
13
12
11
10
9
8
PDRIVE
NC
VIN
CT
INT VCC
ITH
SENSE
NDRIVE
NC
PGND
SGND
SHUTDOWN
NC
SENSE+
LTC1148HV-3.3
+ 1F
1000pF 0.1
SHUTDOWN
L150H
Q2, Si9410DY
D1MBRS140T3
Q1Si9430DY
+ CIN22F35V2
VIN4V TO 18V
+
COUT220F10V
VOUT3.3V/1A
CC3300pF
RC1k
CT270pF
CINCOUTL1R1
Q1Q2
AVX (Ta) TPSE226K035R0300AVX (Ta) TPSE227K010R0080COILTRONICS CTX50-4 Kool MCOREIRC LR2010-01-R100-G
SILICONIX PMOS Si9430DYSILICONIX NMOS Si9410DY
AN54 F28A
Figure 28A. LTC1148HV-3.3: (4V-18V to 3.3V/1A)High Voltage Buck Converter
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Application Note 54
LTC1148HV: (12.5V-18V to 12V/2A) High VoltageBuck Converter
Figure 29A is another application of the LTC1148HV whichis configured as a step-down converter to provide 12V/2A
output. With this low dropout regulator, the input can goas low as 12.5V and still produce a regulated output.Resistors R2 and R3 set the output voltage level.
OUTPUT CURRENT (A)
0.001
EFFICIENCY(%)
100
95
90
85
80
75
70
65
600.01 0.1
AN54 F29B
1 10
Figure 29B. LTC1148HV: (16V to 12V/2A) High VoltageBuck Converter Measured Efficiency
C1 (Ta)
C7 SANYO (OS-CON) 16SA150M
Q1 SILICONIX PMOS BVDSS= 20V RDSON= 0.100 CRSS = 400pF Qg= 50nCQ2 SILICONIX NMOS BVDSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 30nCD1 MOTOROLA SCHOTTKY VBR = 40V
R2 KRL SL-1-C1-0R050J Pd = 1W
L1 COILTRONICS CTX47-5P
ITH
CT
LTC1148HV
VIN
SENSE +
SENSE
+
C60.01F
100pF
+
VIN12.5V
TO 18V
C11F
R11k
C43300pFX7R
C5150pFNPO
10
4
1
8
7
9
14
Q1Si9430DY
Q2Si9410DY
D1MBRS140T3
C322F x 235V
47H
R20.05
432k
1%
12V2A
C7150F 3 16V
3
11
12
SHUTDOWN
6
C20.1F
+
AN54 F29A
SGND PGND
PDRIVE
VFB
NDRIVE
49.9k1%
Figure 29A. LTC1148HV: (12.5V-18V to 12V/2A) High Voltage Buck Converter
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Application Note 54
AN54-32
Figure
30A.
LTC1142:(6.
5V-14Vt
o
3.
3V/2A,
5V/2A,
12V/0.
15A)Triple
OutputBuckConverter
AN54
F30A
2
SHUTDOWN3
25
CT3
27
ITH3
26
INTVCC3
16
SHUTDOWN5
11
CT5
13
ITH5
12
INTVCC5
5
NC
4
PGND3
22
NC
23
PDRIVE3
7
NC
6
NDRIVE3
1
SENSE+3
28
SENSE3
9
PDRIVE5
21
NC
20
NDRIVE5
15
SENSE+5
14
SENSE5
8
NC
18
PGND5
19
NC
SGND3
SGND5
VIN5
VIN3 1
7
3
24
10
LTC1142
C4
3300pF R
8
510
C17
200pF
50V
C1
3300pF
R7
510
C16
390pF
50V
C14
1
F
50V
C15
1
F
50V
C19
1000pF
R5
18k
SHDN
4
NC4
6
NC6
7
NC7
VOUT
ADJ
21
5
VIN
GND
LT1121CS8
C10
20pF
R3649
k
1% R4294
k
1%
Q1
VN7002
1 2
3
38
C9
22
F
25V
+
Q3
Si9410DY
D2
MBRS140+
C6
22
F
25V
+
C7
22
F
25V
R2
100
R1
100
R10
0.0
40
+
C20
220
F
10V
+
C21
220
F
10V
10
9
8
7
1
2
3
4
D3
MBRS140R
622
C13
1000pF
C5
0.1
F
30
H,
2A
LPE-6562-A
026
+
C8
22
F
35V
Q5
Si9410DY
D1
MBRS14
0+
C2
22
F25V
+
C3
22
F
25V
3
2
4
1
L133
H
2ACTX
33-4
+
C11
100
F
10V
R9
0.0
50
+
C12
100
F
10V
+
+
12VENABLE
VIN
SHUTDOWN
(TTLINPUT)
SHUTDOWN
(TTLINPUT)
+VIN
6.5
VTO14V
Q4
Si9430DY
Q2
Si9430DY 4
0V=
12VOFF
>3V=
12VON
(6VMAX)
DONOTFLOAT
C18
2
200pF
T1
6 51.8
TSHUTDOWNPINS2AND16MUSTACTIVELYBEDRIVEN
EITHERHIGHORLOW
ANDNOT
ALLOWEDTOFLOAT
.
+
3.3
V/2A
12V/150mA
C2
,C3
,C6
,C7,
C9
C11
,C12
C20
,C21
L1
AVX(Ta)TPSD226M025R0
200
AVX(Ta)TPSD107K010R0100
AVX(Ta)TPSE227M010R0
100
COILTRONICSCTX33-4
R9
R10
T1
IRCLR2512-R
050
IRCLR2512-R
040
DALE
,LPE-6562-A
O26
5V/2A
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Application Note 54
LTC1142: (6.5V-14V to 3.3V/2A, 5V/2A, 12V/0.15A)Triple Output Buck Converter
LTC1142 is a dual output synchronous switching regula-tor controller. Two independent controller blocks
(LTC1148-based) simultaneously provide 3.3V and 5Voutputs. The circuit in Figure 30A shows an application ofthis IC; it generates triple output voltages with 12V forflash memory programming in addition to the usual logicpower levels. The 3.3V section is a regular buck convertercircuit, the 5V section contains an off-the-shelf trans-former T1 in place of the inductor. The secondary windingis used to boost the output level which is rectified andregulated by an LT1121 to provide a clean and stable 12Voutput. A turns ratio of 1:1.8 is used to ensure that theinput voltage to the LT1121 is high enough to keep theregulator out of dropout. With LTC1142 synchronousswitching, the auxiliary 12V output may be loaded withoutregard to the 5V primary output load as long as the loopremains in continuous operation mode. Continuous op-eration is ensured by R5 which inhibits Burst Modewhenever the 12V output is enabled (enable line goeshigh). Make sure that the enable lines are not floating andare driven by TTL level signals. A circuit board has beenlaid out for this circuit and has subsequently been thor-oughly tested under full operating conditions and opti-mized for mass production requirements. A Gerber file forthe board is available upon request.
OUTPUT CURRENT (A)
0.00160
EFFICIENCY(%)
65
100
0.01 2.5
AN54 F30B
0.1
80
1
90
70
75
85
95
LTC1142-3.3VIN= 8V
LTC1142-5VIN= 8V
Figure 30B. LTC1142:(6.5V-14V to 3.3V/2A, 5V/2A,12V/0.15A) Triple Output Buck ConverterMeasured Efficiency
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Application Note 54
AN54-34
LTC1142HV: (6.5V-18V to 3.3V/2A, 5V/2A, 12V/0.15A)High Voltage Triple Output Buck Converter
Figure 31A shows the same configuration as Figure 30Ausing the high voltage LTC1142HV. Circuit operation isidentical, but now it can accept up to 18V at the input.
OUTPUT CURRENT (A)
0.00160
EFFICIENC
Y(%)
65
100
0.01 2.5
AN54 F30B
0.1
80
1
90
70
75
85
95
LTC1142-3.3VIN= 8V
LTC1142-5VIN= 8V
Figure 31B. LTC1142HV: (6.5V-18V to 3.3V/2A, 5V/2A,12V/0.15A) Measured Efficiency
Figure 31A. LTC1142HV: (6.5V-18V to 3.3V/2A, 5V/2A, 12V/0.15A) High Voltage Triple Output Buck Converter
+
+ +
1000pF
PDRIVE3
SENSE+3
SENSE3
NDRIVE3
PGND3 SGND3 CT3 ITH3 ITH5 CT5 SGND5 PGND5
NDRIVE5
SENSE5
SENSE+5
PDRIVE5
VIN3 SHUTDOWN 3 SHUTDOWN 5 VIN5
LTC1142HV
CT5200pF
4 3 25 27 13 11 17 18
510
3300pF 3300pFCT3390pF
510
1F
224 16 10
9
15
14
20
23
1
28
6
VOUT55V/2A
C4220F
10V 2
22F35V
RSENSE50.04
1.8T30H
D2MBRS140
Q3Si9410DY
0V = NORMAL>1.5V = SHUTDOWN
1F
C222F25V 2
C122F25V 2
VIN6.5V TO18V
Q4Si9430DY
Q5Si9410DY
D1MBRS140
C3100F10V 2
L133H
RSENSE30.05VOUT3
3.3V/2A
AN54F31A
++
Q2Si9430DY
2000pF
C1, C2C3, C4L1RSENSE3RSENSE5T1
AVX (Ta) TPS226K035R0300AVX (Ta) TPSD227K010R0100COILTRONICS CTX33-4KRL SL-C1-1/2-0R050JKRL SL-C1-1/2-0R040JDALE LPE-6562-A026 PRIMARY: SECONDARY = 1:1.8
22
R1100
T1
12V ENABLE0V = 12V OFF>3V = 12V ON
(6V MAX)
1000pF
D3MBRS140
R3660k
R4300k
20pF+
22F25V
12V/150mA
LT1121
VOUT
SHUTDOWN
VIN
ADJ
R2100
Q1VN7002
R518k
+
GND
+
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Application Note 54
LTC1148: High Efficiency Charger Circuit
The LTC1148 regulator can be used as a highly efficientbattery charging device. Figure 32 shows a circuit that isprogrammable for 1.3A fast charge or 100mA tricklecharge mode. During the fast charge interval, the resistordivider network (R4 and R5) forces the LTC1148 feedbackpin below 1.25V causing the regulator to operate at themaximum output current. Sense resistor R3 controls thecurrent at approximately 1.3A. When the batteries aredisconnected, the error amplifier sets the output voltage tobe 8.1V (for proper operation this voltage should exceed
maximum possible voltage across the battery pack). Di-ode D2 prevents the batteries from discharging throughthe divider network when the charger is shut down.
Dual rate charging is controlled by Q3 which selects
between fast and trickle charge. When the transistor turnson, R1 limits error amplifier output so that the currentlimiter starts operating at 100mA. If the trickle chargecurrent needs to be altered, adjust R1. With 1.3A outputcurrent, this charger is capable of efficiency in excess of90% which minimizes power dissipated in surface mountcomponents.
C1 (Ta)
C3 AVX (Ta) TPSD226K025R0100 ESR = 0.100 I RMS= 0.775A
C8 AVX (Ta) TPSE227M010R0100 ESR = 0.100I RMS= 1.149A
Q1 SILICONIX PMOS BV DSS= 20V RDSON= 0.125 CRSS = 400pF Qg= 25nC JA= 50C/WQ2 SILICONIX NMOS BV DSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 50nC JA= 50C/WD1, D2 MOTOROLA SCHOTTKY VBR = 40V
R3 KRL SP-1/2-A1-0R100J Pd = 0.75V
L1 COILTRONICS CTX50-4 DCR = 0.175 IDC = 1.350A Kool M CORE
ALL OTHER CAPACITORS ARE CERAMIC
VOUT= 1.25V (1 + R4/R5) = 8.1V
FAST CHARGE = 130mV/R3 = 1.3A
TRICKLE CHARGE = 100mA
EFFICIENCY > 90%
ITH
CT
LTC1148
VIN
SENSE +
SENSE
+
C60.01F
C7100pF
+
VIN8V TO
15VC11F
R2
1k
R1
51
C43300pFX7R
C5200pFNPO
10
0V = NORMAL> 1.5A = SHUTDOWN
4
1
8
7
9
14
Q1Si9430DY
Q2Si9410DY
D1MBRS140T3
D2MBRS340T3
C322F 235V
R30.1
R4274k
1%
VOUT
C8220F 10V
3
11
12
Q3VN2222LL
1TRICKLECHARGE
SHUTDOWN
6
C20.1F
+
L150H
1
2
4
3
AN54 F32
SGND PGND
PDRIVE
VFB
NDRIVE
VBAT4 CELLS
R549.9k1%
Figure 32. LTC1148: High Efficiency Charger Circuit
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Application Note 54
AN54-36
LTC1148: High Voltage Charger Circuit
Figure 33 is a variation of Figure 32. It is designed tocharge 6 cells and uses the LTC1148HV for higher inputvoltages. R4 value has been changed to provide 12.3V
output when the battery is not connected.
C1 (Ta)
C3 AVX (Ta) TPSD226K035R0200 ESR = 0.200 I RMS= 0.663A
C8 AVX (Ta) TPSE107M016R0100 ESR = 0.100I RMS= 1.149A
Q1 SILICONIX PMOS BV DSS= 20V RDSON= 0.125 CRSS = 400pF Qg= 25nC JA= 50C/WQ2 SILICONIX NMOS BV DSS= 30V RDSON= 0.050 CRSS = 160pF Qg= 50nC JA= 50C/W
D1, D2 MOTOROLA SCHOTTKY VBR = 40V
R3 KRL SP-1/2-A1-0R100J Pd = 0.75V
L1 COILTRONICS CTX50-4 DCR = 0.175 IDC = 1.350A Kool M CORE
ALL OTHER CAPACITORS ARE CERAMIC
VOUT= 1.25V (1 + R4/R5) = 12.3V
FAST CHARGE = 120mV/R3 = 1.3A
TRICKLE CHARGE = 100mA
EFFICIENCY > 90%
ITH
CT
LTC1148HV
VIN
SENSE+
SENSE
+
C60.01F
C7100pF
+
VIN12V TO
18VC11F
R21k
R151
C43300pFX7R
C5200pFNPO
10
0V = NORMAL> 1.5A = SHUTDOWN
4
1
8
7
9
14
Q1Si9430DY
Q2Si9410DY
D1MBRS140T3
D2MBRS340T3
C322F 235V
R30.1
R4442k1%
VOUT
C8100F 16V2
3
11
12
Q3VN2222LL
1TRICKLECHARGE
SHUTDOWN
6
C20.1F
+
L150H
1
2
4
3
AN54 F33
SGND PGND
PDRIVE
VFB
NDRIVE
VBAT6 CELLS
R549.9k1%
Figure 33. LTC1148: High Voltage Charger Circuit
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Application Note 54
LTC1142A: High Efficiency Power Supply Providing3.3V/2A with Built-In Battery Charger
Figure 34 implements a high efficiency step-down con-verter with a built-in battery charger using a single IC. Onesection of the dual LTC1142A is used to convert 4-cells to
3.3V/2A in a regular buck configuration. The other sectionis configured in the same way as the battery charger fromFigure 32. It is powered from a wall adapter and providesthe battery with fast or trickle charging rate. When the
adapter is not connected, D3 prevents the battery fromdischarging through the R2/R1 divider network.
Figure 34. LTC1142A: High Efficiency Power Supply Providing 3.3V/2A with Built-In Battery Charger
1000pF
+
+
+
1000pF
PDRIVE1
SENSE+1
SENSE1
NDRIVE1
PGND1 SGND1 CT1 ITH1 ITH2 CT2 SGND2 PGND2
NDRIVE2
SENSE2
VFB2VFB1
SENSE+2
PDRIVE2VIN1 SHUTDOWN 1 SHUTDOWN 2 VIN2
LTC1142A
CT2330pF
5 4 25 27 13 11 18 19
RC21k
RX51
CC13300pF
CC23300pF
CT1200pF
RC11k
0.22F
324 17
100pF 100pF
10
9
15
14
16
20
23
1
28
2
6
VOUT23.3V/2A
VBATT4 CELLSNiCAD
COUT2220F10V 2
RSENSE20.05
P-CHSi9433DY
L225H
D2MBRS140T3
N-CHSi9410DY
0.22F
CIN222F25V 2
CIN122F35V 2
P-CHSi9430DY
N-CHSi9410DY
D1MBRS140T3
D3MBRS340T3
COUT1220F
10V
L150H
RSENSE10.1
R2274k
1%
R484.5k1%
R351k1%
R149.9k
1%
VIN8V TO 18V
FROM WALL ADAPTER0V = CHARGE ON
>1.5V = CHARGE OFF0V = OUTPUT ON
>1.5V = 3.3V OUTPUT OFF
L1L2RSENSE1RSENSE2
COILTRONICS CTX50-4COILTRONICS CTX25-4KRL SL-C1-1/2-1R100J KRL SL-C1-1/2-1R050J
FAST CHARGE = 130mV/RSENSE1= 1.3ATRICKLE CHARGE = 130mV/RSENSE1= 100mA AN54 F34
+
1 FOR TRICKLE CHARGE
VN2222LL
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Application Note 54
AN54-38
LTC1149: Dual Output Buck Converter
The circuit shown in Figure 35A implements the mostelegant approach for dual output regulators that provide3.3V and 5V outputs. It uses a single LTC1149. The
synchronous rectification feature of this chip is used toprovide excellent efficiency, as well as good cross regula-tion between the two outputs. Maximum output power ofthe converter is 17W, which may be drawn in any combi-nation between 3.3V and 5V outputs.
A regular buck regulator is used for producing 3.3V outputwith T1s primary in place of the buck inductor. Thesecondary of T1 forms a boost winding for 5V output. Thetransformer is wound with a simple trifilar winding toensure that the primary is closely coupled to the second-
ary. Superior cross regulation is achieved by the closeprimary-to-secondary coupling and by splitting voltagefeedback paths (resistors R1 and R2 provide feedbacksignals from both 3.3V and 5V outputs). Diodes D1, D2and capacitor C7 comprise a soft-start circuit that causesthe output voltage to increase slowly when the power isfirst applied to the circuit. This circuit prevents overshoot
at the 3.3V output. The transformer used in this exampleis a standard product (see the parts list). A circuit boardhas been laid out for this circuit and has subsequentlybeen thoroughly tested under full operating conditions
and optimized for mass production requirements. A Ger-ber file for the board is available upon request.
Figure 35A. Single LTC1149: Dual Output Buck Converter
VINS/D1/VFB
S/D2
CT
ITH
VO(REG)
VI(REG)
CAP
PGATE
PDRIVE
NGATE
SENSE+
SENSE
RGNDPGND SGND
LTC1149
10
15
6
7
3
5
16
C1256pF
C132.2F
12 14 11
1
4
13
9
8
R524.9k
1%R41k
C80.068F
C3, C4, C15, C16C5, C6, C8, C17R3T1
AVX (Ta) TPSE227M010R 49BCPAAVX (Ta) TPSE226M035R 49BCPAIRC LR512-01-R020FHURRICANE, HL-8700
C102200pF
C111000pF
2
C190.1F
D3
BAS16
C90.047F
C141000pF
D1BAS16
C710F
QP1Si9435DY
R6100
R7100
C201F
4 QP2Si9435DY
+
1
43
6
TP1
5
2
T1HL-8700
VIN
VIN6V TO
24V +C5
22F
+C6
22F
+C17
22F
+C18
22F
R1102k1%
4
R833k
D6BAS16
QN1Si9410DY
D4MBRS140
QN2Si9410DY
+C1220F +C2
220F
+C15220F +C16
220F
+C3220F
D2
BAS16
R2124k1%
+C4220F
VOUT
3.3VOUT
5VOUT
BOLD LINES INDICATE HIGH CURRENT PATHS (SHORT LEADS)
R30.02
D5MBRS140
AN54 F35A
11 T11 T
11 T
Figure 35B. LTC1149: Du