15
Rev. 2.0 March 2019 www.aosmd.com Page 1 of 15 AOZ2262AQI-10 28V/10A Synchronous EZBuck TM Regulator General Description The AOZ2262AQI-10 is a high-efficiency, easy-to-use DC/DC synchronous buck regulator that operates up to 28V. The device is capable of supplying 10A of continuous output current with an output voltage adjustable down to 0.8V (±1.0%). A proprietary constant on-time PWM control with input feed-forward results in ultra-fast transient response while maintaining relatively constant switching frequency over the entire input voltage range. The on-time can be externally programmed up to 1.3μs. The device features multiple protection functions such as V CC under-voltage lockout, cycle-by-cycle current limit, output over-voltage protection, short-circuit protection, and thermal shutdown. The AOZ2262AQI-10 is available in a 4mm x 4mm QFN- 22L package and is rated over a -40°C to +85°C ambient temperature range. Features Wide input voltage range 4V to 28V 10A continuous output current Output voltage adjustable down to 0.8V (±1.0%) Low R DS(ON) internal NFETs 14m high-side 12m low-side Constant On-Time with input feed-forward Programmable on-time up to 1.3μs Selectable PFM light load operation Ceramic capacitor stable Adjustable soft start Ripple reduction Power Good output Integrated bootstrap diode Cycle-by-cycle current limit Short-circuit protection Thermal shutdown Thermally enhanced 4mm x 4mm QFN-22L 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

AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

  • Upload
    others

  • View
    5

  • Download
    0

Embed Size (px)

Citation preview

Page 1: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-1028V/10A Synchronous EZBuckTM Regulator

General DescriptionThe AOZ2262AQI-10 is a high-efficiency, easy-to-useDC/DC synchronous buck regulator that operates up to28V. The device is capable of supplying 10A ofcontinuous output current with an output voltageadjustable down to 0.8V (±1.0%).

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 1.3µs.

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 AOZ2262AQI-10 is available in a 4mm x 4mm QFN-22L package and is rated over a -40°C to +85°C ambienttemperature range.

Features Wide input voltage range

– 4V to 28V

10A continuous output current

Output voltage adjustable down to 0.8V (±1.0%)

Low RDS(ON) internal NFETs

– 14m high-side

– 12m low-side

Constant On-Time with input feed-forward

Programmable on-time up to 1.3µs

Selectable PFM light load operation

Ceramic capacitor stable

Adjustable soft start

Ripple reduction

Power Good output

Integrated bootstrap diode

Cycle-by-cycle current limit

Short-circuit protection

Thermal shutdown

Thermally enhanced 4mm x 4mm QFN-22L 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 March 2019 www.aosmd.com Page 1 of 15

Page 2: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

Typical Application

POWER GROUND

ANALOG GROUND

LX

C3110µF

BST

R2

R1

R3100k

OUTPUT1.05V, 10A

FB

AGND

PGND

VCC

PGOOD

EN

PFM

SS

AOZ2262AQI-10

ONOFF

POWER GOOD

C44.7µF

C50.1µF

L11µH

RTON

CSS

TON ININPUT 4V TO 28V

C222µF

5V

Rev. 2.0 March 2019 www.aosmd.com Page 2 of 15

Page 3: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

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

Pin Description

Part Number Ambient Temperature Range Package Environmental

AOZ2262AQI-10 -40°C to +85°C 22-Pin 4mm x 4mm QFN Green Product

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 for or 20% higher than the nominal regulation voltage. PGOOD is pulled low during soft-start and shut down.

2 ENEnable Input. The AOZ2262AQI-10 is enabled when EN is pulled high. The device shuts down when EN is pulled low.

3 PFMPFM Selection Input. Connect PFM pin to VCC for forced PWM operation. Connect PFM 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 IN Supply Input. IN is the regulator input. All IN pins must be connected together.

12, 13, 14, 15, 19 PGND Power Ground.

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

20 BSTBootstrap Capacitor Connection. The AOZ2262AQI-10 includes an internal bootstrap diode. Connect an external capacitor between BST and LX as shown in the Typical Application 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.

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

1

22 21 20 19 18

7 8 9 1110

2

3

4

5

PGOOD

IN IN IN LX LX

SS

VC

C

BS

T

PG

ND

LX

EN

PFM

AGND

FB

22-Pin 4mm x 4mm QFN(Top View)

17

16

15

13

12

LX

LX

PGND

PGND

PGND

PGND

LXIN14

6TON

Rev. 2.0 March 2019 www.aosmd.com Page 3 of 15

Page 4: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

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(1) -0.3V to 30V

BST to AGND -0.3V to 36V

SS, PGOOD, FB, EN, VCC, PFM 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) 4V to 28V

Output Voltage Range 0.8V 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 4 28 V

VUVLO Under-Voltage Lockout Threshold of VCCVCC risingVCC falling

4.23.9

VV

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

150 µA

IOFF Shutdown Supply Current VEN = 0V 1 20 µA

VFB Feedback VoltageTA = 25°C TA = 0°C to 85°C

0.7920.788

0.8000.800

0.8080.812

VV

Load Regulation 0.5 %

Line Regulation 1 %

IFB FB Input Bias Current 200 nA

Enable

VEN EN Input ThresholdOff thresholdOn threshold 1.6

0.5 VV

VEN_HYS EN Input Hysteresis 100 mV

PFM Control

VPFM PFM Input Threshold PFM Mode thresholdForce PWM threshold 2.5

0.5 VV

VPFMHYS PFM 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 1.3 µs

TOFF_MIN Minimum Off Time 300 ns

Rev. 2.0 March 2019 www.aosmd.com Page 4 of 15

Page 5: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

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

12085

%%

PGOOD Threshold Hysteresis 5 %

Under Voltage and Over Voltage Protection

VPL Under Voltage Threshold FB falling 70 %

TPL Under Voltage Delay Time 32 µs

VPH Over Voltage Threshold FB rising 120 %

Power Stage Output

RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m

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

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

Low-Side NFET Leakage VEN = 0V 10 µA

Over-current and Thermal Protection

ILIM Current Limit VCC = 5V 15 A

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

Rev. 2.0 March 2019 www.aosmd.com Page 5 of 15

Page 6: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

Functional Block Diagram

TONGenerator

ISENSEILIM

Error Comp

ILIM Comp

0.8V

ISENCE (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

PFM

FB

SS

EN

VCC

Light LoadThreshold

ISENSE

Light LoadComp

EN

Rev. 2.0 March 2019 www.aosmd.com Page 6 of 15

Page 7: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

Typical Performance CharacteristicsCircuit of Typical Application. TA = 25°C, VIN = 19V, VOUT = 1V, fs = 450 kHz unless otherwise specified.

Normal Operation

ILX(5A/div)

ILX (10V/div)

VO ripple (50mV/div)

5µs/div

Load Transient 0A to 10A

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)

0 2.0 4.0 6.0 8.0 10.0

Efficiency vs. Load Current

Vin = 6.5V

Vin = 12V

Vin = 19V

Vin = 24V

100

90

80

70

60

50

40

30

20

10

0

VOUT = 1V

Rev. 2.0 March 2019 www.aosmd.com Page 7 of 15

Page 8: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

Detailed DescriptionThe AOZ2262AQI-10 is a high-efficiency, easy-to-use,synchronous buck regulator optimized for notebookcomputers. The regulator is capable of supplying 10A ofcontinuous output current with an output voltageadjustable down to 0.8V. The programmable on-timefrom 100ns to 1.3µs, enables optimizing the configurationfor PCB area and efficiency.

The input voltage of AOZ2262AQI-10 can be as low as4V. The highest input voltage of AOZ2262AQI-10 can be28V. 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 with aceramic 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 AOZ2262AQI-10 is available in 22-pin 4mm x 4mmQFN package.

Enable and Soft Start

The AOZ2262AQI-10 has external soft start feature tolimit in-rush current and ensure the output voltage rampsup smoothly to regulation 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 0.8V. When VSSis higher than 0.8V, the FB voltage is regulated byinternal precise band-gap voltage (0.8V). When VSS ishigher than 3.3V, the PGOOD signal is high. The softstart time can be calculated by the following formula:

TSS(µs) = 330 x CSS(nF)

If CSS is 1nF, the soft start time will be 330µs; if CSS is10nF, the soft start time will be 3.3ms

Figure 1. Soft-Start Sequence of AOZ2262AQI-10

Constant-On-Time PWM Control with Input Feed-Forward

The control algorithm of AOZ2262AQI-10 is constant-on-time PWM Control with input feed-forward.

The simplified control schematic is shown in Figure. 2.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 internal0.8V 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 2. Simplified Control Schematic of AOZ2262AQI-10

VOUT

VSS

VEN

PGOOD

TSS

0.8VREF

VCC Level

3.3V

0.8V

FB Voltage/AC Current Information

CompProgrammableOne-Shot

IN

PWM

+

Rev. 2.0 March 2019 www.aosmd.com Page 8 of 15

Page 9: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

The constant-on-time PWM control architecture is apseudo-fixed frequency with input voltage feed-forward.The internal circuit of AOZ2262AQI-10 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.

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

Figure 3. TON vs. RTON Curves for AOZ2262AQI-10

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 cannot be used as output capacitor.

The AOZ2262AQI-10 senses the low-side MOSFETcurrent and processes it into DC 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 applicable. Thepure ceramic capacitor solution can significantly reducethe output ripple (no ESR caused overshoot andundershoot) and less board area design.

Current-Limit Protection

The AOZ2262AQI-10 uses the current-limit protection byusing RDSON of the lower MOSFET current sensing. Todetect real current information, a minimum constant-off(300ns typical) is implemented after a constant-on time. Ifthe current exceeds the current-limit threshold, the PWMcontroller is not allowed to initiate a new cycle. The actualpeak current is greater than the current-limit threshold byan amount equal to the inductor ripple current. Therefore,the exact current-limit characteristic and maximum loadcapability are a function of the inductor value as well asinput and output voltages. The current limit will keep thelow-side MOSFET ON and will not allow another high-side on-time, until the current in the low-side MOSFETreduces below the current limit.

After 64 switching cycles, the AOZ2262AQI-10 considersthis is a true failed condition and therefore, turns-off bothhigh-side and low-side MOSFETs and latches off. Onlywhen triggered, the enable can restart the AOZ2262AQI-10 again.

TONRTON

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

FSWVOUT

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

On-Time vs. On-Time Resistance(@ VIN=5V~15V)

60 74 88 102 116 130 144 158 172 186 200

11301064

998932866800734668602536470404338272206140

On-Time Resistance (KΩ)

On-

Tim

e (n

S)

VIN=5VVIN=7VVIN=9VVIN=11VVIN=13VVIN=15V

On-Time vs. On-Time Resistance(@ VIN=17V~28V)

60 74 88 102 116 130 144 158 172 186 200

315299283267251235219203187171155139123107

9175

On-Time Resistance (KΩ)

On-

Tim

e (n

S)

VIN=17VVIN=19VVIN=21VVIN=24VVIN=26VVIN=28V

FSW kHz VOUT V

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

6= (3)

Rev. 2.0 March 2019 www.aosmd.com Page 9 of 15

Page 10: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

Output Voltage Under-Voltage Protection

If the output voltage is lower than 70% by over-current orshort circuit, the AOZ2262AQI-10 will wait for 32µs(typical) and turns-off both high-side and low-sideMOSFETs and latches off. Only when triggered, theenable can restart the AOZ2262AQI-10 again.

Output Voltage Over-Voltage Protection

The threshold of OVP is set 20% higher than 0.8V. Whenthe VFB voltage exceeds the OVP threshold, the high-side MOSFET is turned-off and the low-side MOSFETs isturned-on at 1µs, 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 than the nominal regulationvoltage, the PGOOD is pulled low. When the outputvoltage is 20% higher than the nominal regulationvoltage, the PGOOD is also pulled low.

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

Application InformationThe basic AOZ2262AQI-10 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 AOZ2262AQI-10 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 AOZ2262AQI-10. 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 4. 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 4. ICIN vs. Voltage Conversion Ratio

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:

VINIO

f CIN----------------- 1

VOVIN---------–

VO

VIN---------=

ICIN_RMS IOVOVIN--------- 1

VOVIN---------–

=

VOVIN--------- m=

0

0.1

0.2

0.3

0.4

0.5

0 0.5 1m

ICIN_RMS(m)

IO

ILVOf L----------- 1

VOVIN---------–

=

ILpeak IOIL2--------+=

Rev. 2.0 March 2019 www.aosmd.com Page 10 of 15

Page 11: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

High inductance gives low inductor ripple current butrequires a 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 the inductor needs to be checkedfor thermal and efficiency requirements.

Surface mount inductors in different shapes and stylesare available from Coilcraft, Elytone and Murata.Shielded inductors are small and radiate less EMI noise,but they do cost more than unshielded inductors. Thechoice depends 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 the Equivalent 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.

Thermal Management and Layout ConsiderationIn the AOZ2262AQI-10 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 returns to the input capacitor throughground. Current flows in the first loop when the high sideswitch is on. The second loop starts from the inductor, tothe output 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 the inputcapacitor, output capacitor and PGND pin of theAOZ2262AQI-10.

In the AOZ2262AQI-10 buck regulator circuit, the majorpower dissipating components are the AOZ2262AQI-10and output inductor. The total power dissipation of theconverter circuit can be measured by input power minusoutput power.

VO IL ESRCO1

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

=

VO IL1

8 f CO-------------------------=

VO IL ESRCO=

ICO_RMSIL12----------=

Ptotal_loss VIN IIN VO IO–=

Rev. 2.0 March 2019 www.aosmd.com Page 11 of 15

Page 12: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

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

The actual junction temperature can be calculated withpower dissipation in the AOZ2262AQI-10 and thermalimpedance from junction to ambient.

The maximum junction temperature of AOZ2262AQI-10is 150ºC, which limits the maximum load currentcapability.

The thermal performance of the AOZ2262AQI-10 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.

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; Pin 19 (PGND) must beconnected to the ground plane through via.

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.

Pinductor_loss IO2 Rinductor 1.1=

Tjunction Ptotal_loss Pinductor_loss– JA TA+=

Rev. 2.0 March 2019 www.aosmd.com Page 12 of 15

PGND

PG

ND

PG

ND

PG

ND

PG

ND

Vin

Vout

Vout

Page 13: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

Rev. 2.0 March 2019 www.aosmd.com Page 13 of 15

Package Dimensions, QFN4x4-22L, EP2_S

Page 14: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

Rev. 2.0 March 2019 www.aosmd.com Page 14 of 15

AOZ2262AQI-10

Tape and Reel Dimensions, QFN4x4-22L, EP2_S

Carrier Tape

Reel

Tape Size12mm

Reel Sizeø330

Mø330.0

±2.0

Nø79.0±1.0

UNIT: mm

G

M

W1

S

K

H

N

W

V

R

Trailer Tape300mm min.

Components TapeOrientation in Pocket

Leader Tape500mm min.

Hø13.0±0.5

W12.4

+2.0/-0.0

W117.0

+2.6/-1.2

K10.5±0.2

S2.0±0.5

G—

R—

V—

Leader/Trailer and Orientation

UNIT: mm

P1

D1 P2

B0

P0D0

E2

E1

E

A0Feeding Direction

Package A0 B0 K0 E E1 E2D0 D1 P0 P1 P2 T

4.35±0.10 ±0.10

4.35±0.101.10 1.50 1.50 12.00

±0.101.75

±0.055.50

±0.108.00

±0.104.00

±0.052.00

±0.050.30

±0.30+0.10/-0Min.QFN 4x4(12mm)

T

K0

Page 15: AOZ2262AQI-10 - Alpha and Omega Semiconductor · RDS(ON) High-Side NFET On-Resistance VIN = 12V, VCC = 5V 14 m High-Side NFET Leakage VEN = 0V, VLX = 0V 10 µA RDS(ON) Low-Side NFET

AOZ2262AQI-10

Part Marking

Assembly Lot CodeYear & Week Code

ANAA

YW

AOZ2262AQI-10 (QFN4x4)

Part Number Code

LT

As used herein:

1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user.

2. A critical component in any component of a life support, device, or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.

LEGAL DISCLAIMER

Alpha and Omega Semiconductor makes no representations or warranties with respect to the accuracy orcompleteness of the information provided herein and takes no liabilities for the consequences of use of suchinformation or any product described herein. Alpha and Omega Semiconductor reserves the right to make changesto such information at any time without further notice. This document does not constitute the grant of any intellectualproperty rights or representation of non-infringement of any third party’s intellectual property rights.

LIFE SUPPORT POLICY

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

Rev. 2.0 March 2019 www.aosmd.com Page 15 of 15