aoz2255eqi-30 · 2020. 7. 13. · rev 1.2 june 2018 page 7 of 15 aoz2255eqi-30 typical performance...

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Rev 1.2 June 2018 www.aosmd.com Page 1 of 15 AOZ2255EQI-30 28V/12A Synchronous EZBuck TM Regulator General Description The AOZ2255EQI-30 is a high-efficiency, easy-to-use DC/DC synchronous buck regulator that operates up to 28V. The device is capable of supplying 12A of continuous output current with an output voltage adjustable down to 0.8V ±1%. The AOZ2255EQI-30 integrates an internal linear regulator to generate 5.3V V CC from input. If input voltage is lower than 5.3V, the linear regulator operates at low drop output mode, which allows the V CC voltage is equal to input voltage minus the drop-output voltage of the internal linear regulator. 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 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 AOZ2255EQI-30 is available in a 4mm×4mm QFN- 22L package and is rated over a -40°C to +85°C ambient temperature range. Features Wide input voltage range 6.5V to 28V 12A continuous output current Output voltage adjustable down to 0.8V (±1.0%) Low R DS(ON) internal NFETs 11m high-side 7m low-side Constant On-Time with input feed-forward Ceramic capacitor stable Adjustable soft start Integrated bootstrap diode Cycle-by-cycle current limit Short-circuit protection Thermal shutdown Thermally enhanced 4mm x 4mm QFN-22L package Applications Compact desktop PCs Graphics cards Set-top boxes LCD TVs Cable modems Point-of-load DC/DC converters Telecom/Networking/Datacom equipment Typical Application AOZ2255EQI-30 INPUT 6.5V to 28V Output 1V, 12A C3 110µF R1 R2 C2 22µF C5 0.1µF Analog Ground Power Ground Off On VCC EN SS CSS C4 4.7µF BST LX FB AGND PGND L1 1µH IN 5.3V CTON 100pF TON RTON

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  • AOZ2255EQI-3028V/12A Synchronous EZBuckTM Regulator

    General DescriptionThe AOZ2255EQI-30 is a high-efficiency, easy-to-useDC/DC synchronous buck regulator that operates up to28V. The device is capable of supplying 12A ofcontinuous output current with an output voltageadjustable down to 0.8V ±1%.

    The AOZ2255EQI-30 integrates an internal linearregulator to generate 5.3V VCC from input. If inputvoltage is lower than 5.3V, the linear regulator operatesat low drop output mode, which allows the VCC voltage isequal to input voltage minus the drop-output voltage ofthe internal linear regulator.

    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 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 AOZ2255EQI-30 is available in a 4mm×4mm QFN-22L package and is rated over a -40°C to +85°C ambienttemperature range.

    Features Wide input voltage range

    – 6.5V to 28V 12A continuous output current Output voltage adjustable down to 0.8V (±1.0%) Low RDS(ON) internal NFETs

    – 11m high-side– 7m low-side

    Constant On-Time with input feed-forward Ceramic capacitor stable Adjustable soft start Integrated bootstrap diode Cycle-by-cycle current limit Short-circuit protection Thermal shutdown Thermally enhanced 4mm x 4mm QFN-22L package

    Applications Compact desktop PCs Graphics cards Set-top boxes LCD TVs Cable modems Point-of-load DC/DC converters Telecom/Networking/Datacom equipment

    Rev 1.2 June 2018 www.aosmd.com Page 1 of 15

    Typical Application

    AOZ2255EQI-30

    INPUT6.5V to 28V

    Output1V, 12A

    C3110µF

    R1

    R2

    C222µFC5

    0.1µF

    Analog GroundPower Ground

    Off On

    VCC

    EN

    SSCSS

    C44.7µF

    BST

    LX

    FB

    AGND

    PGND

    L11µH

    IN

    5.3V

    CTON100pF

    TON

    RTON

  • AOZ2255EQI-30

    Option Table

    Recommended Start-up Sequence

    Part Number

    PFM / Force PWM for Light Load Operation

    PFM Force PWMAOZ2255EQI-30 VAOZ2255EQI-31 V

    VIN

    EN

    50µs

    Rev 1.2 June 2018 www.aosmd.com Page 2 of 15

  • AOZ2255EQI-30

    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 EnvironmentalAOZ2255EQI-30 -40°C to +85°C 22-Pin 4mm x 4mm QFN Green Product

    Pin Number Pin Name Pin Function

    1 EN Enable Input. The AOZ2255EQI-30 is enabled when EN is pulled high. The device shuts down when EN is pulled low.

    2 FB Feedback Input. Adjust the output voltage with a resistive voltage-divider between the regulator’s output and AGND.3 AGND Analog Ground.

    6 AIN Supply to internal analog function. AIN pin must be connected to IN pins. For noisy operation, it’s better to have a RC filter from IN to AIN for better noise immunity.7, 8, 9 IN Supply Input. IN is the regulator input. All IN pins must be connected together.

    10, 11, 16, 17, 18 LX Switching Node.12, 13, 14, 15 PGND Power Ground.

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

    20 BSTBootstrap Capacitor Connection. The AOZ2255EQI-30 includes an internal bootstrap diode. Connect an external capacitor between BST and LX as shown in 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 SS Soft-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

    ENIN IN IN LX LX

    SS VCC

    BST

    TON

    LX

    FB

    AGND

    NC

    NC

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

    17

    16

    15

    13

    12

    LX

    LX

    PGND

    PGND

    PGND

    PGND

    LXIN14

    6AIN

    Rev 1.2 June 2018 www.aosmd.com Page 3 of 15

    wwww.aosmd.com/web/rohs_compliant.jspwww.aosmd.com/media/AOSGreenPolicy.pdf

  • AOZ2255EQI-30

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

    Notes:1. LX to PGND Transient (t 2V, PFM 0.16 mAIOFF Shutdown Supply Current VEN = 0V 15 A

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

    0.7920.788

    0.8000.800

    0.8080.812 V

    Load Regulation 0.5 %Line Regulation 1 %

    IFB FB Input Bias Current 200 nAEnable

    VEN EN Input ThresholdOff thresholdOn threshold 1.6

    0.5 V

    VEN_HYS EN Input Hysteresis 100 mVModulatorTON_MIN Minimum On Time 60 nsTON_MAX Maximum On Time 2.6 STOFF_MIN Minimum Off Time 300 nsSoft-StartISS_OUT SS Source Current VSS = 0

    CSS = 0.001F to 0.1F7 11 15 A

    Under Voltage and Over Voltage ProtectionVPL Under Voltage Threshold FB falling 70 %TPL Under Voltage Delay Time 32 SVPH Over Voltage Threshold FB rising 120 %

    Rev 1.2 June 2018 www.aosmd.com Page 4 of 15

  • AOZ2255EQI-30

    Power Stage OutputRDS(ON) High-Side NFET On-Resistance VIN = 12V 11 m

    High-Side NFET Leakage VEN = 0V, VLX = 0V 10 ARDS(ON) Low-Side NFET On-Resistance VLX = 12V 7 m

    Low-Side NFET Leakage VEN = 0V 10 AOver-current and Thermal Protection

    ILIM Current Limit 18 A

    Thermal Shutdown Threshold TJ risingTJ falling150100 °C

    Electrical CharacteristicsTA = 25°C, VIN=12V, 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 1.2 June 2018 www.aosmd.com Page 5 of 15

  • AOZ2255EQI-30

    Rev 1.2 June 2018 www.aosmd.com Page 6 of 15

    Functional Block Diagram

    ISENSEILIM

    Error Comp

    ILIM Comp

    0.8V

    ISENSE (AC) FB

    Decode

    OTP

    BST

    AGNDPGND

    ISENSE

    ISENSE (AC)

    CurrentInformationProcessing

    Vcc

    IN

    UVLO

    LDO

    TOFF_MIN

    SR

    Q

    TimerQ

    FB

    SS

    Light LoadThreshold

    ISENSE

    Light LoadComp

    VCC

    EN

    Reference& Bias

    LX

    TON

    TimerQ

    ENTON TONGenerator

  • AOZ2255EQI-30

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

    Normal Operation

    VLX(20V/div)

    ILX (10A/div)

    VO ripple (20mV/div)

    10µs/div

    Load Transient 0A to 12A

    ILX (10A/div)

    VO ripple(100mV/div)

    500µs/div

    Full Load Start-up

    ILX(10A/div)

    (500mV/div)

    EN (5V/div)

    VLX(20V/div)

    1ms/div

    VO

    Short Circuit Protection

    VLX (20V/div)

    ILX(10A/div)

    VO(500mV/div)

    20µs/div

    Effic

    ienc

    y (%

    )

    Output Current (A)0 2.0 4.0 6.0 8.0 12.010.0

    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 1.2 June 2018 www.aosmd.com Page 7 of 15

  • AOZ2255EQI-30

    Detailed DescriptionThe AOZ2255EQI-30 is a high-efficiency, easy-to-use,synchronous buck regulator optimized for notebookcomputers. The regulator is capable of supplying 12A ofcontinuous output current with an output voltageadjustable down to 0.8V.

    The input voltage of AOZ2255EQI-30 can be as low as6.5V. The highest input voltage of AOZ2255EQI-30 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. Protection features includeVCC under-voltage lockout, cycle-by-cycle current limit,output over voltage and under voltage protection, short-circuit protection, and thermal shutdown.

    The AOZ2255EQI-30 is available in 22-pin 4mm×4mmQFN package.

    Input Power Architecture The AOZ2255EQI-30 integrates an internal linearregulator to generate 5.3V (±5%) VCC from input. If inputvoltage is lower than 5.3V, the linear regulator operatesat low drop-output mode; the VCC voltage is equal toinput voltage minus the drop-output voltage of internallinear regulator.

    Enable and Soft StartThe AOZ2255EQI-30 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 0.8V. When VSSis higher than 0.8V, the FB voltage is regulated byinternal precise band-gap voltage (0.8V). The soft-starttime for FB voltage can be calculated by the followingformula:

    TSS(s) = 80 x CSS(nF)

    If CSS is 1nF, the soft-start time will be 80µ seconds; ifCSS is 10nF, the soft-start time will be 800µ seconds.

    Figure 1. Soft Start Sequence of AOZ2255EQI-30

    Constant-On-Time PWM Control with Input Feed-ForwardThe control algorithm of AOZ2255EQI-30 is constant-on-time PWM control with input feed-forward. The simplifiedcontrol schematic is shown in Figure 2. The high-sideswitch on-time is determined solely by a one-shot whosepulse width is inversely proportional to input voltage (IN).The one-shot is triggered when the internal 0.8V is higherthan the combined information of FB voltage and the ACcurrent information of inductor, which is processed andobtained through the sensed low-side MOSFET currentonce it turns-on. The added AC current information canhelp the stability of constant-on time control even withpure ceramic output capacitors, which have very lowESR. The AC current information has no DC offset, whichdoes not cause offset with output load change, which isfundamentally different from other V2 constant-on timecontrol schemes.

    Figure 2. Simplified Control Schematic of AOZ2255EQI-30

    The constant-on-time PWM control architecture is apseudo-fixed frequency with input voltage feed-forward.The internal circuit of AOZ2255EQI-30 sets the on-timeof high-side switch inversely proportional to the IN.

    To achieve the flux balance of inductor, the buckconverter has the equation:

    (1)

    (2)

    VOUT

    VSS

    VSS = 3.3V

    VSS = 0.8V

    +

    ProgrammableOne-Shot

    IN

    Comp

    FB Voltage/AC Current Information

    0.8V

    PWM

    )()(

    VVRTin

    tonon

    onin

    outsw TV

    VF*

    Rev 1.2 June 2018 www.aosmd.com Page 8 of 15

  • AOZ2255EQI-30

    Once the product of Vin*Ton is constant, the switchingfrequency keeps constant and is independent of inputvoltage.

    An external resistor between the IN and TON pins setsthe switching on-time according to the following curves:

    Figure 3. Ton vs. Rton Curves for AOZ2255EQI-30

    A further simplified equation will be:

    If Vo is 1V, Vin is 19V, and set Fs=400kHz. According toeq.(3), Ton=131ns is needed. Finally, use the Ton to Rtoncurve, we can find out Rton is 300k. This algorithmresults in a nearly constant switching frequency despitethe lack of a fixed-frequency clock generator.

    True Current Mode Control The constant-on-time control scheme is intrinsicallyunstable if output capacitor’s ESR is not large enough as

    an effective current-sense resistor. Ceramic capacitorsusually can not be used as output capacitor.

    The AOZ2255EQI-30 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 applicant. Thepure ceramic capacitor solution can significantly reducethe output ripple (no ESR caused overshoot andundershoot) and less board area design.

    Current-Limit Protection The AOZ2255EQI-30 has the current-limit protection byusing Rdson of the low-side MOSFET to be as currentsensing. To detect real current information, a minimumconstant off time (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 a functionof the inductor value and input and output voltages. Thecurrent limit will keep the low-side MOSFET on and willnot allow another high-side on-time, until the current inthe low-side MOSFET reduces below the current limit.

    After 8 switching cycles, the AOZ2255EQI-30 considersthis is a true failed condition and thus turns-off both high-side and low-side MOSFET and shuts down. TheAOZ2255EQI-30 enters hiccup mode to periodicallyrestart the part. When the current limit protection isremoved, the AOZ2255EQI-30 exits hiccup mode.

    Output Voltage Under-Voltage ProtectionIf the output voltage is lower than 70% by over-current orshort circuit, AOZ2255EQI-30 will wait for 32µs (typical)and turns-off both high-side and low-side MOSFET andshuts down. When the output voltage under-voltageprotection is removed, the AOZ2255EQI-30 restartsagain.

    Output Voltage Over-voltage Protection The threshold of OVP is set 20% higher than 0.8V. Whenthe VFB voltage exceeds the OVP threshold, high-sideMOSFET is turned-off and low-side MOSFET is turned-on 1µs, then shuts down. When the output voltage over-voltage protection is removed, the AOZ2255EQI-30restarts again.

    (3)

    Ton vs. Rton @ Vin = 6.5V~16V

    Ton

    (ns)

    Rton (kOhm)

    1100.00

    1000.00

    900.00

    800.00

    700.00

    600.00

    500.00

    400.00

    300.00

    200.00

    100.00

    0.00200 250 300 350250 400 450 500 550 600 650 700 750 800

    Vin=6.5

    Vin=8

    Vin=10

    Vin=12

    Vin=14

    Vin=16

    Ton vs. Rton @ Vin = 18V~28V

    Ton

    (ns)

    Rton (kOhm)

    500.00

    450.00

    400.00

    350.00

    300.00

    250.00

    200.00

    150.00

    100.00

    50.00

    0.00200 250 300 350250 400 450 500 550 600 650 700 750 800

    Vin=18

    Vin=19

    Vin=21

    Vin=24

    Vin=26

    Vin=28

    610)()(

    )()(

    nSTVV

    VVKHzFonin

    outsw

    Rev 1.2 June 2018 www.aosmd.com Page 9 of 15

  • AOZ2255EQI-30

    Application InformationThe basic AOZ2255EQI-30 application circuit is shown inthe Typical Application section. The component selectionis explained below.

    Input CapacitorThe input capacitor must be connected to the IN pins andPGND pin of the AOZ2255EQI-30 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 AOZ2255EQI-30. The voltage rating ofinput capacitor must be greater than maximum inputvoltage plus ripple voltage.

    The input ripple voltage can be approximated byequation 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 itis under the worst current stress. The worst currentstress on 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.

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

    (4)

    (5)

    (6)

    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

    (7)

    (8)

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

    VOVIN---------–

    =

    ILpeak IOIL2

    --------+=

    Rev 1.2 June 2018 www.aosmd.com Page 10 of 15

  • AOZ2255EQI-30

    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 buckconverter 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 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 canbe 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, output capacitor could beoverstressed.

    Thermal Management and Layout ConsiderationIn the AOZ2255EQI-30 buck regulator circuit, highpulsing current flows through two circuit loops. The firstloop starts from the input capacitors, to the IN pin, to theLX pins, to the filter inductor, to the output capacitor andload, 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 side lowside switch 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 theAOZ2255EQI-30.

    In the AOZ2255EQI-30 buck regulator circuit, the majorpower dissipating components are the AOZ2255EQI-30and 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 output current and DCR of inductor andoutput current.

    The actual junction temperature can be calculated withpower dissipation in the AOZ2255EQI-30 and thermalimpedance from junction to ambient.

    The maximum junction temperature of AOZ2255EQI-30is 150ºC, which limits the maximum load currentcapability.

    The thermal performance of the AOZ2255EQI-30 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.

    (9)

    (10)

    (11)

    (12)

    VO IL ESRCO1

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

    =

    VO IL1

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

    VO IL ESRCO=

    ICO_RMSIL12

    ----------=

    (13)

    (14)

    (15)

    Ptotal_loss VIN IIN VO IO–=

    Pinductor_loss IO2 Rinductor 1.1=

    AJAlossinductorlosstotaljunction TPPT )( __

    Rev 1.2 June 2018 www.aosmd.com Page 11 of 15

  • AOZ2255EQI-30

    Layout ConsiderationsSeveral layout tips are listed below for the best electricand 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.Connected 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 resistance thermal conduction path. Connected 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. Keep sensitive signal traces such as feedback tracefar away from the LX pins.

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

    Rev 1.2 June 2018 www.aosmd.com Page 12 of 15

    1

    2

    3

    4

    5

    6

    EN

    FB

    AGND

    NC

    NC

    AIN

    7 9 10

    IN IN

    18192021

    16

    15

    13

    12

    LX

    LX

    LX

    PGND

    PGND

    IN

    22

    14

    PGND

    8IN LX

    11LX

    17

    PGND

    LX

    TON

    BST

    VCCSS

    VOUT

    Cout

    LCVCC Cb

    VOUT

    R1

    R2

    CinVIN

    PGND

  • AOZ2255EQI-30

    Rev 1.2 June 2018 www.aosmd.com Page 13 of 15

    Package Dimensions, QFN 4x4, 22 Lead EP2_S

    TOP VIEW

    SIDE VIEW

    BOTTOM VIEW

    Notes:1. Controlling dimensions are in millimeters. Converted inch dimensions are not necessarily exact.2. Tolerance: ± 0.05 unless otherwise specified.3. Radius on all corners is 0.152 max., unless otherwise specified.4. Package wrapage: 0.012 max.5. No plastic flash allowed on the top and bottom lead surface.6. Pad planarity: ± 0.1027. Crack between plastic body and lead is not allowed.

    RECOMMENDED LAND PATTERN Dimensions in millimeters Dimensions in inches

    UNIT: MM

    Symbols Min. Typ. Max.A

    A1A2E

    E1E2E3D

    D1D2D3L

    L1L2L3L4L5be

    0.800.00

    3.902.951.652.953.900.650.751.100.350.570.230.570.300.170.20

    0.90—

    0.2 REF4.003.051.753.054.000.750.851.200.400.620.280.620.350.270.25

    0.50 BSC

    1.000.05

    4.103.151.853.154.100.850.951.300.450.670.330.670.400.370.30

    Symbols Min. Typ. Max.A

    A1A2E

    E1E2E3D

    D1D2D3L

    L1L2L3L4L5be

    0.0310.000

    0.1530.1160.0650.1160.1530.0260.0290.0430.0140.0220.0090.0220.0120.0070.008

    0.035—

    0.008 REF0.1570.1200.0690.1200.1570.0300.0330.0470.0160.0240.0110.0240.0140.0110.010

    0.020 BSC

    0.0390.002

    0.1610.1240.0730.1240.1610.0340.0370.0510.0180.0260.0130.0260.0160.0150.012

    D2 D3L5

    L1

    L

    E3

    b

    L3

    D1D1

    L4L2

    E2E1

    e

    L5

    DPin #1 DotBy Marking

    E

    A1A

    A2

    0.60

    0.50

    0.45

    0.250.25

    0.22

    3.102.75 3.10

    3.43

    0.270.750.85

    0.250.75

    1.20

    1.00

    0.04

  • AOZ2255EQI-30

    Rev 1.2 June 2018 www.aosmd.com Page 14 of 15

    Tape and Reel Dimensions, QFN 4x4, 22 Lead 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

    A0 Feeding 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

  • AOZ2255EQI-30

    Rev 1.2 June 2018 www.aosmd.com Page 15 of 15

    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.

    Part Marking

    Part Number Part Number Code of MarkingAOZ2255EQI-30 AEEMAOZ2255EQI-31 AEEW

    AEEMOption Code

    Assembly Lot CodeYear & Week Code

    YWLT

    AOZ2255EQI-30(QFN4x4)

    Part Number Code

    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