user guide for ir3891 evaluation board
TRANSCRIPT
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
06-18-2013 1
USER GUIDE FOR IR3891 EVALUATION BOARD
DESCRIPTION
The IR3891 is a dual synchronous buck
converter, providing a compact, high
performance and flexible solution in a small
5mm X 6mm Power QFN package.
Key features offered by the IR3891 include
internal Digital Soft Start, precision 0.5V
reference voltage, Power Good, thermal
protection, programmable switching
frequency, Enable input, input under-voltage
lockout for proper start-up, enhanced line/
load regulation with feed forward, external
frequency synchronization with smooth
clocking, internal LDO, pre-bias start-up,
output over voltage protection as well as openfeedback line protection.
Output over-current protection function isimplemented by sensing the voltage developedacross the on-resistance of the synchronousrectifier MOSFET for optimum cost andperformance and the current limit is thermallycompensated.
This user guide contains the schematic and billof materials for the IR3891 22.6mmx11.6mmevaluation board. The guide describesoperation and use of the evaluation board itself.Detailed application information for IR3891 isavailable in the IR3891 data sheet.
BOARD FEATURES
• Vin = +12.0V
• Fs = 600kHz
• Vout1 = +1.5V @ 3A (100LFM)
• Vout2 = +3.3V @ 3A (100LFM)
• L1 = 2.2uH
• L2 = 4.7uH
• Cin= 2x10uF (ceramic 1206)
• Cout1 = Cout2 = 2x47uF (ceramic 0805)
SupIRBuckTM
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
06-18-20132
A well regulated +12V input supply should be connected to VIN+ and GND. A maximum of 3A load shouldbe connected to Vout1+/GND and Vout2+/GND . The inputs and output connections of the board are listedin Table I.
CONNECTIONS and OPERATING INSTRUCTIONS
LAYOUT
The PCB is a compact 22.6mmx11.6mm, 4-layer board using FR4 material. All layers use 2 Oz. copper.The PCB thickness is 0.062”.
Power supply decoupling capacitors, the bootstrap capacitor and feedback components are locatedclose to IR3891. The feedback resistors are connected to the output at the point of regulation and are
located close to the SupIRBuck IC. To improve efficiency, the circuit board is designed to minimize the
length of the on-board power ground current path.
Table I. Connections
Connection Signal Name
VIN+ Vin (+12V)
Vout1+ Vout1(+1.5V)
Vout2+ Vout2(+3.3V)
Gnd Power Ground
En1 Enable 1
En2 Enable 2
Trim1Vout adjustment for channel 1
Trim2Vout adjustment for channel 2
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
3
Fig. 2: Board Bottom Layer Picture
11.6mm
Fig. 1: Board Top Layer Picture
22.6mm
Trim2 En2 Trim1En1Vin GndGndVout2 Vout1
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
06-18-20134
Fig. 3: Board Layout-Top Layer
Fig. 4: Board Layout-Bottom LayerSingle point connection
between AGnd and PGnd
11.6mm
22.6mm
Trim2 En2 Trim1En1Vin GndGndVout2 Vout1
3.3mm
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
06-18-20135
Fig. 6: Board Layout-Mid Layer 2
Fig. 5: Board Layout-Mid Layer 1
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
06-18-20136
Fig
.7:
Sch
emat
ico
fth
eIR
3891
eval
uat
ion
bo
ard
R5
49.9
k
R6
7.5
k
J1
CO
N9
123456789
VIN
Vou
t2Tr
im2
R13
2.8
7k
Vin
R14
143
R12
5.7
6k
R15
10
C13
2200
pF
C10
0.1u
F
C11
4.7n
F
R16
N/S
R26
N/S
R9
39.2
k
GN
D
GN
D
R11
5.4
9k
U1
IR3
89
1 PVin215
PVin214
EN
28
PGood212R
t/S
ync
7
Vin
3
Seq
6Comp2
11
PGND216
Vsn
s11
Vcc
/LD
O4
FB210
Boot213
GN
D5
Vsn
s29
EN
12
PGND217
PGND218
SW
219
SW
220
SW
121
SW
122
PGND123
PGND124
PGND125
PVin126
Boot128
PGood129
PVin127
Comp130
FB131
C12
2
47uF
C20
0.1u
F
C8
2.2u
F
Trim
1
Single Point Connection between AGND and PGND
L2
4.7
uH
C24
0.1u
F
C14
0.1u
F
C21
1
10uF
C21
2
N/S
EN
2
EN
1
R23
1.2
1k
R24
143
R22
6.8
1k
R25
10
C23
2200
pF
L1
2.2
uH
C11
2
N/S
C6
1.0u
F
Vin
Vou
t1
C11
1
10uF
C12
68pF
C21
4.7n
F
R21
6.0
4k
C22
68pF
R3
49.9
k
R4
7.5
k
C12
3
47uF
C22
3
47uF
Vin
C22
2
47uF
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
06-18-20137
Bill of Materials
Item Qty Part Reference Value Description Manufacturer Part Number
1 2 C111 C211 10uF 1206, 25V, X5R, 20% TDK C3216X5R1E106M
2 2 C13 C23 2200pF 0402, 50V, X5R, 10% TDK C1005X5R1H222K050BA
3 4C10 C20C14 C24
0.1uF 0402, 50V, X5R, 10% TDK C1005X5R1H104K050BB
4 2 C11 C21 4.7nF 0402, 25V, X7R, 10% Murata GRM155R71E472KA01D
5 2 C12 C22 68pF 0402, 50V, NP0, 5% Murata GRM1555C1H680JA01D
6 1 C6 1.0uF 0402, 16V, X5R, 10% TDK C1005X5R1C105K050BC
7 1 C8 2.2uF 0402, 10V, X5R, 10% TDK C1005X5R1A225K050BC
8 4C122 C123 C222
C22347uF 0805, 6.3V, X5R, 20% Murata GRM21BR60J476ME15
9 2 R15 R25 10Ω Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF10R0X
10 2 R14 R24 143Ω Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF1430X
11 1 R12 5.76kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF5761X
12 1 R22 6.81kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF6811X
13 1 R13 2.87kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF2871X
14 1 R23 1.21kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF1211X
15 1 R11 5.49kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF5491X
16 1 R21 6.04kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF6041X
17 2 R3 R5 49.9kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF4992X
18 2 R4 R6 7.5kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF7501X
19 1 R9 39.2kΩ Thick film, 0402, 1/10W, 1% Panasonic ERJ-2RKF3922X
20 1 L1 2.2uH7.1mm x 6.5mmx3.0mm,
DCR=17.3mΩTDK SPM6530T-2R2M
21 1 L2 4.7uH7.1mm x 6.5mmx3.0mm,
DCR=35.8mΩTDK SPM6530T-4R7M
22 1 U1 IR3891 5mm x 6 mm QFNInternational
RectifierIR3891MTRPBF
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
10/16/20138
Fig. 11: Vout1 voltage ripple, 3A loadCh2: Vout1
Fig. 12: Vout2 voltage ripple, 3A loadCh2: Vout2
Fig. 9: Vout1 start up with 0.4V pre bias , 0A Ch2:Vout1
Fig. 8: Start up with Iout1=Iout2=3ACh1:Vin, Ch2:Vout1, Ch4:Vout2
Fig. 10: Vout2 start up with 2.2V pre bias , 0A Ch2:Vout2
Fig. 13: Inductor node of Vout1Ch3: SW node 1
TYPICAL OPERATING WAVEFORMSVin=12.0V, Vout1=1.5V, Vout2=3.3V, Iout1=Iout2=0-3A, Room temperature, 100LFM
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
10/16/20139
Fig. 17: Vout1 transient response to a load step from 1.5A to 3.0ACh2: Vout1, Ch4: Iout1
Fig. 18: Vout2 transient response to a load step from 1.5A to 3.0A
Ch2: Vout2, Ch4: Iout2
Fig. 15: Vout1 short circuit (hiccup) recoveryCh2:Vout1
Fig. 14: Inductor node of Vout2Ch3: SW node 2
Fig. 16: Vout2 short circuit (hiccup) recoveryCh2:Vout2
TYPICAL OPERATING WAVEFORMSVin=12.0V, Vout1=1.5V, Vout2=3.3V, Iout1=Iout2=0-3A, Room temperature, 100LFM
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
06-18-201310
Fig. 19: Bode plot of Vout1 at 3A load shows a bandwidth of 120.54kHz and phase margin of 55.48 degrees
TYPICAL OPERATING WAVEFORMSVin=12.0V, Vout1=1.5V, Vout2=3.3V, Iout1=Iout2=0-3A, Room temperature, 100LFM
-60
-40
-20
0
20
40
60
-200
-150
-100
-50
0
50
100
150
200
103 104 105
TR
1/d
B TR
2/°
f/HzTR1: Mag(Gain) TR2: Unwrapped Phase(Gain)
Fig. 20: Bode plot of Vout2 at 3A load shows a bandwidth of 111.89kHz and phase margin of 53.34 degrees
-60
-40
-20
0
20
40
60
-200
-150
-100
-50
0
50
100
150
200
103 104 105
TR
1/d
B TR
2/°
f/HzTR1: Mag(Gain) TR2: Unwrapped Phase(Gain)
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
06-18-201311
Fig. 22: Power loss versus load current
Fig. 21 : Efficiency versus load current
TYPICAL OPERATING WAVEFORMSVin=12.0V, Vout1=1.5V, Vout2=3.3V, Iout1=Iout2=0-3A, Room temperature, 100LFM
IRDC3891-P1V5/P3V3
Preliminary
This evaluation board is a preliminary version meant for the engineering evaluation of the IR3891. Based on the results of the continuing evaluation, this board can evolve and change without notice
06-18-201312
Fig. 23: Thermal Image of the board with Iout1=Iout2=3A IR3891: 76.08oC Ambient: 26.04oC
TYPICAL OPERATING WAVEFORMSVin=12.0V, Vout1=1.5V, Vout2=3.3V, Iout1=Iout2=0-3A, Room temperature, 100LFM