aoz2261nqi-11aoz2261nqi-11 rev. 2.0 june 2019 page 2 of 18 typical application lx c3 88µf bst r2...

AOZ2261NQI-1128V/8A Synchronous EZBuckTM Regulator

General DescriptionThe AOZ2261NQI-11 is a high-efficiency, easy-to-useDC/DC synchronous buck regulator that operates up to28V. The device is capable of supplying 8A of continuousoutput current with an output voltage adjustable down to0.6V ±1%.

A proprietary constant on-time PWM control with inputfeed-forward results in ultra-fast transient response whilemaintaining relatively constant switching frequency overthe entire input voltage range. The on time can beexternally programmed up to 2.6µs.

The device features multiple protection functions such asVCC under-voltage lockout, cycle-by-cycle current limit,output over-voltage protection, short-circuit protection,and thermal shutdown.

The AOZ2261NQI-11 is available in a 4mm×4mm QFN-23L package and is rated over a -40°C to +85°C ambienttemperature range.

Features Wide input voltage range

– 2.7V to 28V

8A continuous output current

Output voltage adjustable down to 0.6V (±1.0%)

Low RDS(ON) internal NFETs

– 28m high-side

– 11m low-side

Constant On-Time with input feed-forward

Programmable on-time up to 2.6µs

Selectable PFM light-load operation

Ceramic capacitor stable

Adjustable soft start

Ripple reduction

Discharge Function

Power Good output

Integrated bootstrap diode

Adjustable cycle-by-cycle current limit

Short-circuit protection

Over-voltage protection

Thermal shutdown

Thermally enhanced 4mm x 4mm QFN-23L package

Applications Portable computers

Compact desktop PCs

Servers

Graphics cards

Set-top boxes

LCD TVs

Cable modems

Point-of-load DC/DC converters

Telecom/Networking/Datacom equipment

Rev. 2.0 June 2019 www.aosmd.com of 18

AOZ2261NQI-11

Typical Application

LX

C388µF

BST

R2

R1

R3100k

OUTPUT1.05V, 8A

FB

AGND

PGND

VCC

PGOOD

EN/DISCHG

MODE

SS

ONOFF

POWER GOOD

C44.7µF

C50.1µF

L11µH

RTON

CSS

TON ININPUT 2.7V to 28V

C222µF

5V

OCS

ROCS

AOZ2261NQI-11

POWER GROUND

ANALOG GROUND


AOZ2261NQI-11

Ordering Information

AOS Green Products use reduced levels of Halogens, and are also RoHS compliant.Please visit www.aosmd.com/media/AOSGreenPolicy.pdf for additional information.

Pin Configuration

Part Number Ambient Temperature Range Package Environmental

AOZ2261NQI-11 -40°C to +85°C 23-Pin 4mm x 4mm QFN Green Product

23-Pin 4mm x 4mm QFNTop View

1

2

3

4

5

6

PGOOD

MODE

AGND

FB

TON

7 9 10

IN IN

18192021

LX

OC

S

BST

VCCSS

16

15

13

12

LX

LX

LX

PGND

PGND

IN

23

14

PGND8

IN LX

11LX

17

PGND

EN/DISCHG

IN22


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http://www.aosmd.com/media/AOSGreenPolicy.pdf

http://www.aosmd.com/web/quality/rohs_compliant.jsp

AOZ2261NQI-11

Pin Description

Pin Number Pin Name Pin Function

1 PGOOD

Power Good Signal Output. PGOOD is an open-drain output used to indicate the status of the output voltage. It is internally pulled low when the output voltage is 15% lower than the nominal regulation voltage or 50% higher than the nominal regulation voltage. PGOOD is pulled low during soft-start and shut down.

2 EN/DISCHG

Enable Input. The AOZ2261NQI-11 is enabled when EN is pulled high. The device shuts down when EN is pulled low. Set voltage level higher/lower than discharge threshold when PGOOD pull high to enable/disable output discharge function.

3 MODEPFM Selection Input. Connect MODE pin to VCC for forced PWM operation. Connect MODE pin to ground for PFM operation to improve light load efficiency.

4 AGND Analog Ground.

5 FBFeedback Input. Adjust the output voltage with a resistive voltage-divider between the regulator’s output and AGND.

6 TON On-Time Setting Input. Connect a resistor between VIN and TON to set the on time.

7, 8, 9, 22 IN Supply Input. IN is the regulator input. All IN pins must be connected together.

12, 13, 14, 15 PGND Power Ground.

10, 11, 16, 17, 18 LX Switching Node.

19OCS

Current limitation level setting pin. Connect a resistor between OCS and GND to set over current protection level. No capacitor is allowed between OCS and AGND.

20 BSTBootstrap Capacitor Connection. The AOZ2261NQI-11 includes an internal bootstrap diode. Connect an external capacitor between BST and LX as shown in the TypicalApplication diagram.

21 VCCSupply Input for analog functions. Bypass VCC to AGND with a 4.7µF~10µF ceramic capacitor. Place the capacitor close to VCC pin.

23 SSSoft-Start Time Setting Pin. Connect a capacitor between SS and AGND to set the soft-start time.


AOZ2261NQI-11

Absolute Maximum RatingsExceeding the Absolute Maximum Ratings may damage the device.

Notes:

1. LX to PGND Transient (t<20ns) ------ -7V to VIN + 7V.

2. Devices are inherently ESD sensitive, handling precautions are required. Human body model rating: 1.5k in series with 100pF.

Maximum Operating RatingsThe device is not guaranteed to operate beyond the Maximum Operating Ratings.

Parameter Rating

IN, TON to AGND -0.3V to 30V

LX to AGND(2) -0.3V to 30V

BST to AGND -0.3V to 36V

SS, OCS, PGOOD, FB to AGND -0.3V to 6V

EN/DISCH, VCC, MODE to AGND -0.3V to 6V

PGND to AGND -0.3V to +0.3V

Junction Temperature (TJ) +150°C

Storage Temperature (TS) -65°C to +150°C

ESD Rating(2) 2kV

Parameter Rating

Supply Voltage (VIN) 2.7V to 28V

Output Voltage Range 0.6V to 0.85*VIN

Ambient Temperature (TA) -40°C to +85°C

Package Thermal Resistance (θJA)

32°C/W

Electrical CharacteristicsTA = 25°C, VIN = 12V, VCC = 5V, EN = 5V, unless otherwise specified. Specifications in BOLD indicate a temperature range of -40°C to +85°C.

Symbol Parameter Conditions Min. Typ. Max Units

VIN IN Supply Voltage 2.7 28 V

VUVLO Under-Voltage Lockout Threshold of VCCVCC risingVCC falling 3.2

4.23.9

4.5 VV

Iq Quiescent Supply Current of VCC IOUT = 0A, VEN > 2V, PFM mode 350 µA

IOFF Shutdown Supply Current VEN = 0V 1 20 µA

VFB Feedback Voltage TA = 25°C 0.594 0.600 0.606 V

Load Regulation 0.5 %

Line Regulation 1 %

IFB FB Input Bias Current 200 nA

Enable/Discharge

VEN EN Input ThresholdOff thresholdOn threshold 1.2

0.5 VV

VEN_HYS EN Input Hysteresis 100 250 mV

VDIS Discharge Threshold When PGOOD from 0 to 1 1.5 V

MODE Control

VMODE MODE Input Threshold PFM Mode thresholdForce PWM threshold 1.2

0.5 VV

VMODEHYS MODE Input Hysteresis 100 mV

Modulator

TON On Time RTON = 100k, VIN = 12V 200 ns

TON_MIN Minimum On Time 100 ns

TON_MAX Maximum On Time 2.6 µs

TOFF_MIN Minimum Off Time 300 ns


AOZ2261NQI-11

Soft-Start

ISS_OUT SS Source Current VSS = 0V CSS = 0.001µF to 0.1µF

7 11 15 µA

Power Good Signal

VPG_LOW PGOOD Low Voltage IOL = 1mA 0.5 V

PGOOD Leakage Current ±1 µA

VPGH PGOOD Threshold(Low Level to High Level)

FB rising 90 %

VPGL PGOOD Threshold(High Level to Low Level)

FB risingFB falling

15085

%%

PGOOD Threshold Hysteresis 5 %

Under Voltage and Over Voltage Protection

VPL Under Voltage Threshold FB falling 50 %

TPL Under Voltage Delay Time 32 µs

VPH Over Voltage Threshold FB rising 150 %

Power Stage Output

RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 28 m

High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA

RDS(ON) Low-Side NFET On-Resistance VLX = 12V, VCC = 5V 11 m

Low-Side NFET Leakage VEN = 0V 10 µA

Thermal Protection

Thermal Shutdown ThresholdTJ risingTJ falling

150100

°C°C

Electrical CharacteristicsTA = 25°C, VIN = 12V, VCC = 5V, EN = 5V, unless otherwise specified. Specifications in BOLD indicate a temperature range of -40°C to +85°C.

Symbol Parameter Conditions Min. Typ. Max Units


AOZ2261NQI-11

Functional Block Diagram

TONGenerator

Error Comp

ILIM Comp

0.6V

ISENSE (AC) FB

Decode

OTP

Reference& Bias

BST

PG Logic

LX

AGNDPGND

ISENSE

ISENSE (AC)

CurrentInformationProcessing

Vcc

IN PGood

UVLO

TON

TimerQ

TOFF_MIN

SR

Q

TimerQ

TON

MODE

FB

SS

EN/DIS

VCC

Light LoadThreshold

ISENSE

Light LoadComp Discharge

Pulse

ENDIS_On

OCS +

LX

DISCHARGE



AOZ2261NQI-11

Typical Performance CharacteristicsTA = 25°C, VIN = 19V, VOUT = 1V, fS = 450kHz, unless otherwise specified.

Normal Operation

VLX(10V/div)

ILX(5A/div)

VO ripple(50mV/div)

5µs/div

Load Transient 0A to 8A

ILX(5A/div)

VO ripple(50mV/div)

2ms/div

Full Load Start-up

ILX(5A/div)

VO

(500mV/div)

EN(5V/div)

VLX(20V/div)

1ms/div

Short Circuit Protection

VLX(20V/div)

ILX(10A/div)

VO

(500mV/div)

50µs/div

Eff

icie

ncy

(%

)

Output Current (A)

100

90

80

70

60

50

40

30

20

10

00 1.0 2.0 3.0 4.0 6.05.0 7.0 8.0

Efficiency vs. Load Current

Vin = 6.5V

Vin = 12V

Vin = 19V

Vin = 24V

VOUT = 1V

AOZ2261NQI-11

Detailed DescriptionThe AOZ2261NQI-11 is a high-efficiency, easy-to-use,synchronous buck regulator optimized for notebookcomputers. The regulator is capable of supplying 8A ofcontinuous output current with an output voltageadjustable down to 0.6V. The programmable on-timefrom 100ns to 2.6µs enables optimizing the configurationfor PCB area and efficiency.

The input voltage of AOZ2261NQI-11 can be as low as2.7V. The highest input voltage of AOZ2261NQI-11 canbe 28V. Constant on-time PWM with input feed-forwardcontrol scheme results in ultra-fast transient responsewhile maintaining relatively constant switching frequencyover the entire input range. True AC current mode controlscheme guarantees the regulator can be stable withceramics output capacitor. The switching frequency canbe externally programmed. Protection features includeVCC under-voltage lockout, current limit, output overvoltage and under voltage protection, short-circuitprotection, and thermal shutdown.

The AOZ2261NQI-11 is available in 23-pin 4mm×4mmQFN package.

Enable and Soft Start

The AOZ2261NQI-11 has external soft start feature tolimit in-rush current and ensure the output voltage rampsup smoothly to regulate voltage. A soft start processbegins when VCC rises to 4.5V and voltage on EN pin isHIGH. An internal current source charges the externalsoft-start capacitor; the FB voltage follows the voltage ofsoft-start pin (VSS) when it is lower than 0.6V. When VSSis higher than 0.6V, the FB voltage is regulated byinternal precise band-gap voltage (0.6V). When VSS ishigher than 1.2V, the PGOOD signal is high. The soft-start time for PGOOD can be calculated by the followingformula:

TSS(µs) = 120 x CSS(nF)

If CSS is 1nF, the soft-start time will be 120µs; if CSS is3.6nF, the soft-start time will be 432µs.

Figure 1. Soft-Start Sequence of AOZ2261NQI-11

Enable and Discharge Function

AOZ2261NQI-11 pin 2 is a multi-function pin, whichcombines enable and discharge function together.Discharge function on/off is determined by the voltagelevel on this pin at PGOOD rising edge. Figure 2illustrates how to activate discharge function. OncePGOOD signal rises up, AOZ2261NQI-11 detects thevoltage on EN/DIS pin. Discharge function will beactivated (Dis_on set to 1) only if EN/DIS pin voltage isunder discharge threshold at that moment. Dis_on keepshigh until next PGOOD rising edge and will beoverwritten. Discharge function won’t be activated(Dis_on set to 0) if EN/DIS pin voltage is over dischargethreshold at PGOOD rising edge. Dis_on keeps low untilnext PGOOD rising edge and will be overwritten.

AOZ2261NQI-11 enters discharge mode if Dis_on signalis high when EN/DIS pin voltage is lower than EN offthreshold. Discharge MOSFET is always turn-on duringdischarge mode. At the mean while, low-side MOSFETturns on and off to quickly discharge output voltage. Allprotection and COT are disabled during discharge mode.Discharge mode operation ended when FB voltage isunder 40mV.

VOUT

VSS

VEN

PGOOD

TSS

0.6VREF

VCC Level

1.2V


AOZ2261NQI-11

Figure 2. AOZ2261NQI-11 Discharge Function On/Off Setting

EN/DIS

PGOOD

Dis_on

No PGOODOne shot,DischargeMode keep disabled

Discharge mode notactivated

No PGOODOne shot,DischargeMode keepactivated

Discharge mode

activated

Discharge threshold= 1.5V

EN on threshold = 1.2V

EN off threshold = 0.9V

Constant-On-Time PWM Control with Input FeedForward

The control algorithm of AOZ2261NQI-11 is constant-on-time PWM Control with input feed-forward.

The simplified control schematic is shown in Figure. 3.The high-side switch on-time is determined solely by aone-shot whose pulse width can be programmed by oneexternal resistor and is inversely proportional to inputvoltage (IN). The one-shot is triggered when the internal0.6V is higher than the combined information of FBvoltage and the AC current information of inductor, whichis processed and obtained through the sensed lower-sideMOSFET current once it turns-on. The added AC currentinformation can help the stability of constant-on timecontrol even with pure ceramic output capacitors, whichhave very low ESR. The AC current information has noDC offset, which does not cause offset with output loadchange, which is fundamentally different from other V2

constant-on time control schemes.

Figure 3. Simplified Control Schematic of AOZ2261NQI-11

The constant-on-time PWM control architecture is apseudo-fixed frequency with input voltage feed-forward.The internal circuit of AOZ2261NQI-11 sets the on-timeof high-side switch inversely proportional to the IN.

To achieve the flux balance of inductor, the buck converter has the equation:

Once the product of VIN x TON is constant, the switchingfrequency keeps constant and is independent with inputvoltage.

0.6V

FB Voltage/AC Current Information

Comp

IN

PWM

+

–Programmable

One-Shot

TON

RTON

VIN V ------------------------- (1)

FSW

VOUT

VIN TON---------------------------= (2)


AOZ2261NQI-11

An external resistor between the IN and TON pin sets theswitching on-time according to the following curves:

Figure 4. TON vs. RTON Curves

A further simplified equation will be:

If VOUT is 1.05V, VIN is 19V, and set FS = 500kHz.According to equation 3, TON = 110ns is needed. Finally,use the TON to RTON curve, we can find out RTON is82k.

This algorithm results in a nearly constant switchingfrequency despite the lack of a fixed-frequency clockgenerator.

True Current Mode Control

The constant-on-time control scheme is intrinsicallyunstable if output capacitor’s ESR is not large enough asan effective current-sense resistor. Ceramic capacitorsusually can not be used as output capacitor.

The AOZ2261NQI-11 senses the low-side MOSFETcurrent and processes it into DC current and AC currentinformation using AOS proprietary technique. The ACcurrent information is decoded and added on the FB pinon phase. With AC current information, the stability ofconstant-on-time control is significantly improved evenwithout the help of output capacitor’s ESR; and thus thepure ceramic capacitor solution can be applied. The pureceramic capacitor solution can significantly reduce theoutput ripple (no ESR caused overshoot and undershoot)and less board area design.

Current-Limit Protection

The AOZ2261NQI-11 has the current-limit protection byusing RDS(ON) of the low-side MOSFET to be as currentsensing. To detect real current information, a minimumconstant off (300ns typical) is implemented after aconstant on time. If the current exceeds the current-limitthreshold, the PWM controller is not allowed to initiate anew cycle. The actual peak current is greater than thecurrent-limit threshold by an amount equal to the inductorripple current. Therefore, the exact current-limitcharacteristic and maximum load capability are afunction of the inductor value and input and outputvoltages. The current limit will keep the low-sideMOSFET on and will not allow another high-side on-time,until the current in the low-side MOSFET reduces belowthe current limit.

Current-Limit Setting

The current-limit threshold mentioned in last paragraphcan be set by connecting a resistor between OCS pinand ground. The value of the current limit resistor (ROCS)can be calculated according to the equation below. Acapacitor from OCS pin to ground would impact thecurrent limit accuracy and is not allowed.

As shown in Figure 5, once the magnitude of switch nodevoltage VLX is larger than VOCS, over current signal istriggered. The larger ROCS is, the higher over currentthreshold will be. Section Current-Limit Protectiondescribes the action when over current conditionhappens.

FSW kHz VOUT V

VIN V TON ns ------------------------------------------------ 10

6= (3)

IL_LIMIT A 0.909 ROCS k = (4)


AOZ2261NQI-11

Figure 5. Illustration of Current Limit Setting

Output Voltage Under-Voltage Protection

If the output voltage is lower than 50% by over-current orshort circuit, AOZ2261NQI-11 will wait for 32µs (typical)and turns-off both high-side and low-side MOSFETs andlatches off. Only when triggered, the enable can restartthe AOZ2261NQI-11 again.

Output Voltage Over-Voltage Protection

The threshold of OVP is set 50% higher than 0.6V. Whenthe VFB voltage exceeds the OVP threshold, high-sideMOSFET is turn-off and low-side MOSFETs is turn-on1µs, then latch-off.

Power Good Output

The power good (PGOOD) output, which is an opendrain output, requires the pull-up resistor. When theoutput voltage is 15% below the nominal regulationvoltage, the PGOOD is pulled low. When the outputvoltage is 50% higher than the nominal regulationvoltage, the PGOOD is also pull low.

When combined with the under-voltage-protection circuit,this current limit method is effective in almost everycircumstance.

Ripple Reduction

When switching frequency is down to half of settingduring PFM, AOZ2261NQI-11 actively reduces on-timepulse width to reduce inductor current ripple and outputvoltage ripple. Ripple reduction not only reduces half ofvoltage ripple but also decreases the chance of acousticnoise under light load.

Application InformationThe basic AOZ2261NQI-11 application circuit is shown inpage 2. Component selection is explained below.

Input Capacitor

The input capacitor must be connected to the IN pins andPGND pin of the AOZ2261NQI-11 to maintain steadyinput voltage and filter out the pulsing input current. Asmall decoupling capacitor, usually 4.7µF, should beconnected to the VCC pin and AGND pin for stableoperation of the AOZ2261NQI-11. The voltage rating ofinput capacitor must be greater than maximum inputvoltage plus ripple voltage.

The input ripple voltage can be approximated by equation below:

Since the input current is discontinuous in a buckconverter, the current stress on the input capacitor isanother concern when selecting the capacitor. For a buckcircuit, the RMS value of input capacitor current can becalculated by:

if let m equal the conversion ratio:

The relation between the input capacitor RMS currentand voltage conversion ratio is calculated and shown inFigure 6. It can be seen that when VO is half of VIN, CIN isunder the worst current stress. The worst current stresson CIN is 0.5 x IO.

Figure 6. ICIN vs. Voltage Conversion Ratio

OCL signal

LX = -IL x RDS(ON)

IREF

ROCS

OCS

GND

OCL level ROCS

VIN

IOf CIN----------------- 1

VO

VIN

---------– VO

VIN

---------= (5)

ICIN_RMS IOVO

VIN

--------- 1VO

VIN

---------–

= (6)

VO

VIN

--------- m= (7)

0

0.1

0.2

0.3

0.4

0.5

0 0.5 1m

ICIN_RMS(m)

IO


AOZ2261NQI-11


For reliable operation and best performance, the inputcapacitors must have current rating higher than ICIN-RMSat worst operating conditions. Ceramic capacitors arepreferred for input capacitors because of their low ESRand high ripple current rating. Depending on theapplication circuits, other low ESR tantalum capacitor oraluminum electrolytic capacitor may also be used. Whenselecting ceramic capacitors, X5R or X7R type dielectricceramic capacitors are preferred for their bettertemperature and voltage characteristics. Note that theripple current rating from capacitor manufactures isbased on certain amount of life time. Further de-ratingmay be necessary for practical design requirement.

Inductor

The inductor is used to supply constant current to outputwhen it is driven by a switching voltage. For given inputand output voltage, inductance and switching frequencytogether decide the inductor ripple current, which is:

The peak inductor current is:

High inductance gives low inductor ripple current butrequires larger size inductor to avoid saturation. Lowripple current reduces inductor core losses. It alsoreduces RMS current through inductor and switches,which results in less conduction loss. Usually, peak topeak ripple current on inductor is designed to be 30% to50% of output current.

When selecting the inductor, make sure it is able tohandle the peak current without saturation even at thehighest operating temperature.

The inductor takes the highest current in a buck circuit.The conduction loss on inductor needs to be checked forthermal and efficiency requirements.

Surface mount inductors in different shape and styles areavailable from Coilcraft, Elytone and Murata. Shieldedinductors are small and radiate less EMI noise. But theycost more than unshielded inductors. The choicedepends on EMI requirement, price and size.

Output Capacitor

The output capacitor is selected based on the DC outputvoltage rating, output ripple voltage specification andripple current rating.

The selected output capacitor must have a higher ratedvoltage specification than the maximum desired outputvoltage including ripple. De-rating needs to beconsidered for long term reliability.

Output ripple voltage specification is another importantfactor for selecting the output capacitor. In a buck con-verter circuit, output ripple voltage is determined byinductor value, switching frequency, output capacitorvalue, and ESR. It can be calculated by the equationbelow;

where CO is output capacitor value and ESRCO is theEquivalent Series Resistor of output capacitor.

When a low ESR ceramic capacitor is used as outputcapacitor, the impedance of the capacitor at theswitching frequency dominates. Output ripple is mainlycaused by capacitor value and inductor ripple current.The output ripple voltage calculation can be simplified to:

If the impedance of ESR at switching frequencydominates, the output ripple voltage is mainly decided bycapacitor ESR and inductor ripple current. The outputripple voltage calculation can be further simplified to:

For lower output ripple voltage across the entireoperating temperature range, X5R or X7R dielectric typeof ceramic, or other low ESR tantalum are recommendedto be used as output capacitors.

In a buck converter, output capacitor current iscontinuous. The RMS current of output capacitor isdecided by the peak to peak inductor ripple current. It can be calculated by:

Usually, the ripple current rating of the output capacitor isa smaller issue because of the low current stress. Whenthe buck inductor is selected to be very small andinductor ripple current is high, the output capacitor couldbe overstressed.

ILVO

f L----------- 1

VO

VIN---------–

= (8)

ILpeak IOIL2--------+= (9)

VO IL ESRCO1

8 f CO-------------------------+

= (10)

VO IL1

8 f CO-------------------------= (11)

VO IL ESRCO=

ICO_RMS

IL

12----------= (13)

(12)

AOZ2261NQI-11

Thermal Management and Layout ConsiderationIn the AOZ2261NQI-11 buck regulator circuit, highpulsing current flows through two circuit loops. The firstloop starts from the input capacitors, to the VIN pin, tothe LX pins, to the filter inductor, to the output capacitorand load, and then return to the input capacitor throughground. Current flows in the first loop when the high sideswitch is on. The second loop starts from inductor, to theoutput capacitors and load, to the low side switch.Current flows in the second loop when the low sideswitch is on.

In PCB layout, minimizing the two loops area reduces thenoise of this circuit and improves efficiency. A groundplane is strongly recommended to connect inputcapacitor, output capacitor, and PGND pin of theAOZ2261NQI-11.

In the AOZ2261NQI-11 buck regulator circuit, the majorpower dissipating components are the AOZ2261NQI-11and the output inductor. The total power dissipation ofconverter circuit can be measured by input power minusoutput power.

The power dissipation of inductor can be approximatelycalculated by DCR of inductor and output current.

The actual junction temperature can be calculated withpower dissipation in the AOZ2261NQI-11 and thermalimpedance from junction to ambient.

The maximum junction temperature of AOZ2261NQI-11is 150ºC, which limits the maximum load currentcapability.

The thermal performance of the AOZ2261NQI-11 isstrongly affected by the PCB layout. Extra care should betaken by users during design process to ensure that theIC will operate under the recommended environmentalconditions.

Ptotal_loss VIN IIN VO IO–= (14)

Pinductor_loss IO2 Rinductor 1.1= (15)

Tjunction Ptotal_loss Pinductor_loss– JA= +TA

(16)


AOZ2261NQI-11

Layout Considerations

Several layout tips are listed below for the best electric and thermal performance.

1. The LX pins and pad are connected to internal lowside switch drain. They are low resistance thermalconduction path and most noisy switching node.Connect a large copper plane to LX pin to helpthermal dissipation.

2. The IN pins and pad are connected to internal highside switch drain. They are also low resistancethermal conduction path. Connect a large copperplane to IN pins to help thermal dissipation.

3. Input capacitors should be connected to the IN pinand the PGND pin as close as possible to reduce theswitching spikes.

4. Decoupling capacitor CVCC should be connected toVCC and AGND as close as possible.

5. Voltage divider R1 and R2 should be placed as closeas possible to FB and AGND.

6. RTON should be connected as close as possible toPin 6 (TON pin).

7. A ground plane is preferred.

8. Keep sensitive signal traces such as feedback tracefar away from the LX pins.

9. Pour copper plane on all unused board area andconnect it to stable DC nodes, like VIN, GND orVOUT.

10. The current limit resistor (ROCS) should be connectedas close as possible to Pin 19 (OCS). Place three GNDvias to connect to inner ground layer. Keep distancebetween Rocs and Lx plane.


VOUT

PGND

123456

PGO

ODEN

MO

DE

AGNDFB

TON

7

9

10

IIN

IN

LX

OCS

BST

VCC

SS

16151312

LXLX

LX

PGN

D

PGN

D

IN14

PGND

8IN

LX

11LX

17

PGN

D

VIN

IN

GND

VOUT

GND

AGND

18

19

20

21

22

23


AOZ2261NQI-11

Package Dimensions, QFN 4x4B, 23 Lead EP2_S

D2D1

A1

E

E2

DIMENSIONS IN MILLIMETERS

MINSYMBOLS

ANOM MAX

DIMENSIONS IN INCHES

MIN NOM MAX

E1

RECOMMENDED LAND PATTERN

UNIT: mm

D3LL1

NOTE1. CONTROLLING DIMENSION IS MILLIMETER. CONVERTED INCH DIMENSIONS ARE NOT NECESSARILY EXACT.2. TOLERANCE :±0.05 UNLESS OTHERWISE SPECIFIED.3. RADIUS ON ALL CORNER ARE 0.152 MAX., UNLESS OTHERWISE SPECIFIED.4. PACKAGE WARPAGE: 0.012 MAX.5. NO ANY PLASTIC FLASH ALLOWED ON THE TOP AND BOTTOM LEAD SURFACE.6. PAD PLANARITY: ±0.1027. CRACK BETWEEN PLASTIC BODY AND LEAD IS NOT ALLOWED.

A2

eb

L2L3

E3D

L4

Option 1

Option 2


AOZ2261NQI-11

Tape and Reel Dimensions, QFN 4x4B, 23 Lead EP2_S

AOZ2261NQI-11

Part Marking

Y W L T

AOZ2261NQI-11(QFN 4x4)

A L N B

Year & Week Code Assembly Lot Code

Part Number Code

As used herein:

1. Life support devices or systems are devices orsystems which, (a) are intended for surgical implant intothe body or (b) support or sustain life, and (c) whosefailure to perform when properly used in accordancewith instructions for use provided in the labeling, can bereasonably expected to result in a significant injury ofthe user.

2. A critical component in any component of a lifesupport, device, or system whose failure to perform canbe reasonably expected to cause the failure of the lifesupport device or system, or to affect its safety oreffectiveness.

LIFE SUPPORT POLICY

ALPHA AND OMEGA SEMICONDUCTOR PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS.

LEGAL DISCLAIMER

Applications or uses as critical components in life support devices or systems are not authorized. AOS does not assume any liability arising out of such applications or uses of its products. AOS reserves the right to make changes to product specifications without notice. It is the responsibility of the customer to evaluate suitability of the product for their intended application. Customer shall comply with applicable legal requirements, including all applicable export control rules, regulations and limitations.

AOS' products are provided subject to AOS' terms and conditions of sale which are set forth at:http://www.aosmd.com/terms_and_conditions_of_sale


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