aoz2152eqi-30the aoz2152eqi-30 is a high-efficiency, easy-to-use dc/dc synchronous buck regulator...

AOZ2152EQI-3028V/6A Synchronous EZBuckTM Regulator

General DescriptionThe AOZ2152EQI-30 is a high-efficiency, easy-to-useDC/DC synchronous buck regulator that operates up to28V. The device is capable of supplying 6A of continuousoutput current with an output voltage adjustable down to0.8V ±1%.

The AOZ2152EQI-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 AOZ2152EQI-30 is available in a 3mm×3mm QFN-18L package and is rated over a -40°C to +85°C ambienttemperature range.

Features Wide input voltage range

– 6.5V to 28V

6A continuous output current

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

Low RDS(ON) internal NFETs

– 28m high-side

– 11m 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 3mm x 3mm QFN-18L 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 September 2018 www.aosmd.com of 15

Typical Application

AOZ2152EQI-30

INPUT6.5V to 28V

Output3.3V, 6A

C388µF

R1

R2

C222µFC5

0.1µF

Analog Ground

Off On

VCC

EN

SSCSS

C44.7µF

BST

LX

FB

AGND

PGND

L11.5µH

IN

5.3V

CTON

100pF

TON

RTON

Power Ground

AOZ2152EQI-30

Option Table

Recommended Start-up Sequence

Part Number

PFM / Force PWM for Light Load Operation

PFM Force PWM

AOZ2152EQI-30 V

AOZ2152EQI-31 V

VIN

EN

50µs


AOZ2152EQI-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 Environmental

AOZ2152EQI-30 -40°C to +85°C 18-Pin 3mm x 3mm QFN Green Product

Pin Number Pin Name Pin Function

1 ENEnable Input. The AOZ2152EQI-30 is enabled when EN is pulled high. The device shuts down when EN is pulled low.

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

3 AGND Analog Ground.

4, 5, 6, 7, 8 IN Supply Input. IN is the regulator input. All IN pins must be connected together.

9, 13, 14 LX Switching Node.

10, 11, 12 PGND Power Ground.

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

16 BSTBootstrap Capacitor Connection. The AOZ2152EQI-30 includes an internal bootstrap diode. Connect an external capacitor between BST and LX as shown in the Typical Application diagram.

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

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

1

2

3

4

5

6 7 8 910

11

12

13

14151617

EN

FB

AGND

IN

IN

IN IN IN LXPGND

PGND

PGND

LX

LXT

ON

BS

T

VC

CIN LX

18S

S

18-Pin 3mm x 3mm QFN(Top View)


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

www.aosmd.com/media/AOSGreenPolicy.pdf

AOZ2152EQI-30

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 MaximumOperating 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, FB, EN, VCC 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) 6.5V to 28V

Output Voltage Range 0.8V to 0.85*VIN

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

Package Thermal ResistanceJA)JC)

40°C/W6°C/W

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

Symbol Parameter Conditions Min. Typ. Max Units

VIN IN Supply Voltage 6.5 28 V

VUVLO Under-Voltage Lockout ThresholdVCC risingVCC falling 3.2

4.03.7

4.4V

Iq Quiescent Supply Current of VCC IOUT = 0, VEN > 2V, PFM 0.16 mA

IOFF 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 nA

Enable

VEN EN Input ThresholdOff thresholdOn threshold 1.6

0.5V

VEN_HYS EN Input Hysteresis 300 mV

Modulator

TON_MIN Minimum On Time 60 ns

TON_MAX Maximum On Time 2.6 s

TOFF_MIN Minimum Off Time 300 ns

Soft-Start

ISS_OUT SS Source Current VSS = 0 CSS = 0.001F to 0.1F

7 11 15 A

Under Voltage and Over Voltage Protection

VPL Under Voltage Threshold FB falling 70 %

TPL Under Voltage Delay Time 32 s

VPH Over Voltage Threshold FB rising 120 %


AOZ2152EQI-30

Power Stage Output

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

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

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

Low-Side NFET Leakage VEN = 0V 10 A

Over-current and Thermal Protection

ILIM Current Limit 9 A

Thermal Shutdown ThresholdTJ risingTJ falling

150100

°C

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

Symbol Parameter Conditions Min. Typ. Max Units


AOZ2152EQI-30

Functional Block Diagram

ISENSE

ILIM

Error Comp

ILIM Comp

0.8V

ISENSE (AC) FB

Decode

OTP

BST

AGNDPGND

ISENSECurrentInformationProcessing

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

ISENSE (AC)


AOZ2152EQI-30

Typical Performance CharacteristicsCircuit of Typical Application. TA = 25°C, VIN = 19V, VOUT = 3.3V, unless otherwise specified.

Normal Operation

VLX(20V/div)

ILX(10A/div)

VO ripple(100mV/div)

10µs/div

Load Transient 0A to 6A

ILX(10A/div)

VO ripple(200mV/div)

500µs/div

Full Load Start-up

ILX(10A/div)

VO

(2V/div)

EN(5V/div)

VLX(20V/div)

1ms/div

Short Circuit Protection

VLX(20V/div)

ILX(10A/div)

VO

(2V/div)

5µs/div

VOUT = 3.3V

Eff

icie

ncy

(%

)

Output Current (A)

100

95

90

85

80

75

700 1.0 2.0 4.03.0 5.0 6.0

Efficiency vs. Load Current

Vin = 6.5V

Vin = 12V

Vin = 19V

Vin = 24V


AOZ2152EQI-30

Detailed DescriptionThe AOZ2152EQI-30 is a high-efficiency, easy-to-use,synchronous buck regulator optimized for notebookcomputers. The regulator is capable of supplying 6A ofcontinuous output current with an output voltageadjustable down to 0.8V.

The input voltage of AOZ2152EQI-30 can be as low as6.5V. The highest input voltage of AOZ2152EQI-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 AOZ2152EQI-30 is available in 18-pin 3mm×3mmQFN package.

Input Power Architecture

The AOZ2152EQI-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 Start

The AOZ2152EQI-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 AOZ2152EQI-30

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

The control algorithm of AOZ2152EQI-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 AOZ2152EQI-30

The constant-on-time PWM control architecture is apseudo-fixed frequency with input voltage feed-forward.The internal circuit of AOZ2152EQI-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

)(

)(

VV

RT

in

tonon

onin

outsw TV

VF

*


AOZ2152EQI-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 AOZ2152EQI-30

A further simplified equation will be:

If Vo is 1V, Vin is 19V, and set Fs=400kHz. According toeq.(3), Ton=131.6nS is needed. Finally, use the Ton toRton curve, 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 AOZ2152EQI-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 AOZ2152EQI-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 AOZ2152EQI-30 considersthis is a true failed condition and thus turns-off both high-side and low-side MOSFET and shuts down. TheAOZ2152EQI-30 enters hiccup mode to periodicallyrestart the part. When the current limit protection isremoved, the AOZ2152EQI-30 exits hiccup mode.

Output Voltage Under-Voltage Protection

If the output voltage is lower than 70% by over-current orshort circuit, AOZ2152EQI-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 AOZ2152EQI-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 AOZ2152EQI-30restarts again.

(3)

TO

N (

nS

)

RTON (kOhm)

TON vs. RTON @ VIN=6.5V ~ 16V

TO

N (

nS

)

RTON (kOhm)

TON vs. RTON @ VIN=18V ~ 28V

610)()(

)()(

nSTVV

VVKHzF

onin

outsw

AOZ2152EQI-30

Application InformationThe basic AOZ2152EQI-30 application circuit is shown inthe Typical Application section. The component selectionis explained below.

Input capacitor

The input capacitor must be connected to the IN pins andPGND pin of the AOZ2152EQI-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 AOZ2152EQI-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.

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.

(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

--------+=


AOZ2152EQI-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 AOZ2152EQI-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 theAOZ2152EQI-30.

In the AOZ2152EQI-30 buck regulator circuit, the majorpower dissipating components are the AOZ2152EQI-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 AOZ2152EQI-30 and thermalimpedance from junction to ambient.

The maximum junction temperature of AOZ2152EQI-30is 150ºC, which limits the maximum load currentcapability.The thermal performance of the AOZ2152EQI-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 )( __


AOZ2152EQI-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.


VIN

PGND

VOUT

1

2

3

4

5

6 7 8 9

10

11

12

13

14

151617

EN

FB

AGND

IN

IN

IN IN IN LX

PGND

PGND

PGND

LX

LX

BS

T

VC

C

IN LX

18S

S

VOUT

CVCC

Cout

Cin

TO

N

AOZ2152EQI-30

Package Dimensions, QFN 3x3, 18 Lead EP2_S

RECOMMENDED LAND PATTERN

UNIT: mm

NOTECONTROLLING DIMENSION IS MILLIMETER.CONVERTED INCH DIMENSIONS ARE NOT NECESSARILY EXACT.

1


AOZ2152EQI-30

Tape and Reel Dimensions, QFN 3x3, 18 Lead EP2_S

Carrier Tape

Reel

Leader/Trailer & Orientation


AOZ2152EQI-30

Part Marking

Part Number Part Number Code of Marking

AOZ2152EQI-30 ACEM

AOZ2152EQI-31 ACEW

Option Code

Assembly Lot CodeYear & Week Code

YWLTPart Number Code

AOZ2152EQI-30(QFN 3x3)

A C EM

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 or completeness of the information provided herein and takes no liabilities for the consequences of use of such information or any product described herein. Alpha and Omega Semiconductor reserves the right to make changes to such information at any time without further notice. This document does not constitute the grant of any intellectual property 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.


aoz2152eqi-30the aoz2152eqi-30 is a high-efficiency, easy-to-use dc/dc synchronous buck regulator...

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