ame · ame 5 ame5254 rev. a.01 c 1.5mhz, 2a, synchronous ste p-down dc/dc converter ie n absolute m...

AME

1

AME5254

Rev. A.01

C

1.5MHz, 2A, SynchronousStep-Down DC/DC Converter

i e

l High Efficiency: Up to 95%

l 1.5MHz Constant Switching Frequency

l Integrated Main Switches and Synchronous

Rectifier. No Schottky Diode Required.l Shutdown Current: <1µAl 2.7V to 5.5V Input Voltage Range

l Output Voltage as Low as 0.6V

l 100% Duty Cycle in Dropoutl Quiescent Current : 45µA (TYP.)l Slope Compensated Current Mode Control

for Excellent Line and Load Transient Re- sponse

l Short Circuit Protectionl Green Products Meet RoHS Standards

The AME5254 is a high efficiency monolithic synchro-nous buck regulator using a constant frequency, currentmode architecture. The device is available in an adjust-able version. Supply current with no load is 45µA anddrops to <1µA in shutdown.

The 2.7V to 5.5V input voltage range makes theAME5254 ideally suited for single Li-Ion, two to four AAbattery-powered applications. 100% duty cycle provideslow dropout operation, extending battery life in portablesystems. In power saving mode, 45µA quiescent cur-rent is very suitable for DSP/MCU in standby operation;and in PWM mode, low output ripple voltage is goodenough for noise sensitive applications. The two modescan be automatically switched according to the load cur-rent. Switching frequency is internally set at 1.5MHz,allowing the use of small surface mount inductors andcapacitors.

The internal synchronous switch increases efficiencyand eliminates the need for an external schottky diode.Low output voltages are easily supported with the 0.6Vfeedback reference voltage. The AME5254 is available ina small SOT-25 package and SOT-26 package.

n General Description n Features

n Applications

n Typical Application

l Smart Phonesl Set Top Boxl Personal Information Appliancesl Wireless and DSL Modemsl MP3 Playersl Portable Instruments

IN

EN

SW

FBGND

2.2µH

L1

COUT

10µF

CIN

4.7µF

VIN2.7V to 5.5V VOUT

C1R1

R2

AME5254

Figure 1. Typical Step-Down RegulatorCFWD:22pF~220pF

VOUT=VFB(R1+R2)/R2

AME

2

AME5254

Rev. A.01


n Function Block Diagram

Figure 2. Founction Block Diagram

EN

LX

Current Sense

Zero DetectorUVLO &

Power GoodDetector

VREF

Control Logic

VIN

Driver

RC

COMP

ErrorAmplifer

PWMComparator

GND

RS2

RS1

FB /VOUT

SlopeCompensation

OSC &Shutdown Control

CurrentLimit Detector

AME

3

AME5254

Rev. A.01

C


i e

n Pin Configuration

SOT-25Top View

AME5254-AEVxxx1. EN2. GND3. LX4. IN5. FB

Die Attach:Conductive Epoxy

1 32

5 4

AME5254

1 32

6 45

AME5254

AME5254-AEYxxx1. EN2. GND3. LX4. IN5. NC6. FB

Die Attach:Conductive Epoxy

SOT-26Top View

n Pin Description

SOT-25 SOT-26

1 1 EN

Regulator Enable control input.Drive LX above 1.25V to turn on the part. Drive LX below 0.55V toturn it off. In shutdown, all functions are disabled drawing <1�Asupply current. Do not leave LX floating.

2 2 GND Ground connection pin.

3 3 LXPower Switch Output.It is the Switch node connection to Inductor. This pin connects to thedrains of the internal P-CH and N-CH MOSFET switches.

4 4 INSupply Input Pin.Must be closely decoupled to GND, Pin 2, with a 2.2�F or greaterceramic capacitor.

NA 5 NC No connect.

5 6 FBFeedback Input Pin.Connect FB to the center point of the external resistor divider.The feedback threshold voltage is 0.6V.

PinName

Pin No.Pin Description

AME

4

AME5254

Rev. A.01


AME5254 - x x x xxx

Pin Configuration

Package Type

Number of Pins

Output Voltage

n Ordering Information

A 1. EN E: SOT-2X V: 5 ADJ: Adjustable(SOT-25) 2. GND Y: 6

3. LX4. IN5. FB

A 1. EN(SOT-26) 2. GND

3. LX4. IN5. NC6. FB

Pin Configuration Package Type Number of Pins Output Voltage

AME

5

AME5254

Rev. A.01

C


i e

n Absolute Maximum Ratings

Symbol Maximum Unit

VIN -0.3 to 6

EN, VOUT Voltages VEN, VOUT -0.3 to VIN

SW Voltage VSW -0.3 to VIN

ESD Classification

Parameter

Input Supply Voltage

B*

V

Caution:Street above the listed absolute maximum rating may cause permanent damage to the device.

* HBM B:2000V~3999V

n Recommended Operating Conditions

Parameter Symbol Rating Unit

Input Voltage VIN 2.7 to 5.5 V

Ambient Temperature Range TA -40 to +85 oC

Junction Temperature Range TJ -40 to +125 oC

Storage Temperature Range TSTG -65 to +150 oC

n Thermal Information

Parameter Package Die Attach Symbol Maximum Unit

Thermal Resistance*(Junction to Case)

θJC 81

Thermal Resistance(Junction to Ambient)

θJA 260

Internal Power Dissipation PD 400 mW

260 oC

SOT-25SOT-26

Conductive Epoxy

oC / W

Solder Iron (10Sec)**

*Measure θJC on backside center of Exposed Pad.

**MIL-STD-202G 210F

AME

6

AME5254

Rev. A.01


n Electrical Specifications

Parameter Symbol Min Typ Max Units

Input Voltage Range VIN 2.7 5.5 V

Quiescent Current IQ 45 90 �A

Shutdown Current ISD 1 �A

2.5 2.7 V

200 mV

2 2.3 V

Regulated Feedback Voltage VFB 0.588 0.6 0.612 V

FB Input Bias Current IFB 200 nA

Regulated Output VoltageAccuracy

VOUT -3 3 %

Output Voltage Range VOUT VFB VIN V

Current Limit ILIM 3 A

Output Voltage LineRegulation LNR 0.3 3 %V

Output Voltage LoadRegulation LDR -2 2 %

Oscillator Frequency fOSC 1.2 1.5 1.8 MHz

RDS(ON) of P-ChannelMOSFET

RDS(ON)_P 0.13 0.15 �

RDS(ON) of N-ChannelMOSFET

RDS(ON)_N 0.08 0.10 �

SW Leakage Current ILSW ±0.1 ±1 �A

EN High-Level Input Voltage VEN_H 1 V

EN Low-Level Input Voltage VEN_L 0.80 V

EN Leakage Current IEN -0.01 0.01 �A

Start up Time TS 500 650 �S

Over Temperature Protection TOTP 150 °C

OTP Hysteresis TOTH 30 °C

Maximum Duty Cycle ISHORT 100 %

VIN=3.6V, IOUT = 100mA

IDS = 100mA

IDS = 100mA

VBOOT-GND=30V,VPHASE=25V,VPVCC

From Enable to OutputRegulation

Test Condition

Adjustable output range

No load

VEN = 0V

No Load

VOUT = 1V

IOUT = 0 to 2A ,VIN = 2.7 to 5.5V

TA = -40°C to 85°C

VIN = 2.7V to 5.5V,IOUT = 100mA

IOUT = 1mA to 2A

UVLO Threshold VUVLO Hysteresis

VIN Falling

VIN Rising

AME

7

AME5254

Rev. A.01

C


i e

n Detailed DescriptionCurrent Mode PWM Control

Slope compensated current mode PWM control pro-vides stable switching and cycle-by-cycle current limitfor excellent load and line responses and protection ofthe internal main switch(P-Channel MOSFET) and syn-chronous rectifier (N-Channel MOSFET). During normaloperation, the internal P-Channel MOSFET is turned onfor a certain time to ramp the inductor current at eachrising edge of the internal oscillator, and switched off whenthe peak inductor current is above the error voltage. Thecurrent comparator, ICOMP, limits the peak inductor cur-rent. When the main switch is off, the synchronous recti-fier will be turned on immediately and stay on until eitherthe inductor current starts to reverse, as indicated by thecurrent reversal comparator, IZERO, or the beginning of thenext clock cycle. The OVDET comparator controls outputtransient overshoots by turning the main switch off andkeeping it off until the fault is no longer present.

Power Saving Mode Operation

At very light loads, the AME5254 automatically entersPower Saving Mode. In power saving mode at light load,a control circuit puts most of the circuit into sleep in or-der to reduce quiescent current and improve efficiency atlight load. When the output voltage drops to certain thresh-old, the control circuit turns back on the oscillator andthe PWM control loop, boosting output backup. When anupper threshold is reached, the control circuit again putsmost of circuit into sleep, reducing quiescent current.During Power Saving Mode operation, the converter posi-tions the output voltage slightly higher than the nominaloutput voltage during PWM operation, allowing additionalheadroom for voltage drop during a load transient fromlight to heavy load. While the power saving mode im-proves light load efficiency, however, with the turning onand off, the noise or ripple voltage is larger than that in thePWM Mode.

Dropout Operation

As the input supply voltage decreases to a value ap-proaching the output voltage, the duty cycle increasestoward the maximum on-time. Further reduction of thesupply voltage forces the main switch to remain on formore than one cycle until it reaches 100% duty cycle.The output voltage will then be determined by the inputvoltage minus the voltage drop across the P-ChannelMOSFET and the inductor.

AME

8

AME5254

Rev. A.01


n Application InformationInductor Selection

For a given input and output voltage, the inductor valueand operating frequency determine the ripple current.The ripple current DIL increases with higher VIN and de-creases with higher inductance.

( )( ) ��

�

��

�−=∆

IN

OUTOUTL V

VV

LfI 1

1

A reasonable starting point for setting ripple current is∆IL. The DC current rating of the inductor should be atleast equal to the maximum load current plus half theripple current to prevent core saturation. For better effi-ciency, choose a low DC-resistance inductor.

CIN and COUT Selection

The input capacitance, CIN is needed to filter the trap-ezoidal current at the source of the top MOSFET. Toprevent large voltage transients, a low ESR inputcapacitorsized for the maximum RMS current must beused. The maximum RMS capacitor current is given by:

1)( −=OUT

IN

IN

OUTMAXOUTRMS V

VV

VII

This formula has a maximum at VIN=2VOUT, whereIRMS=IOUT/2. This simple worst-case condition is com-monly used for design because even significant devia-tions do not offer much relief. Note that the capacitormanufacturer ripple current ratings are often based on2000 hours of life. This makes it advisable to furtherderate the capacitor, or choose a capacitor rated at ahigher temperature than required.

The selection of COUT is determined by the effectiveseries resistance(ESR) that is required to minimize volt-age ripple and load step transients. The output ripple,VOUT, is determined by:

��

��

�+∆≅∆

OUTLOUT fC

ESRIV8

1

Using Ceramic Input and Output Capacitors

Higher values, lower cost ceramic capacitors are nowbecoming available in smaller case sizes. Their high ripplecurrent, high voltage rating and low ESR make them idealfor switching regulator applications. However, care mustbe taken when these capacitors are used at the input andoutput. When a ceramic capacitor is used at the inputand the power is supplied by a wall adapter through longwires, a load step at the output can induce ringing at theinput, VIN. At best, this ringing can couple to the outputand be mistaken as loop instability. At worst, a suddeninrush of current through the long wires can potentiallycause a voltage spike at VIN large enough to damage thepart.

Output Voltage Programming

The output voltage is set by an external resistive divideraccording to the following equation :

��

��

�+×=

2

11RR

VV REFOUT

Where VREF equals to 0.6V typical. The resistive dividerallows the FB pin to sense a fraction of the output voltageas shown in Figure 3.

AME5254

FB

GND

R1

R2

5.5VVOUT0.6V ≤≤

Figure 3: Setting the AME5254 Output Voltage

AME

9

AME5254

Rev. A.01

C


i e

Over-Temperature Protection

Thermal protection completely disables switchingwhen internal dissipation becomes excessive. Thejunction over-temperature threshold is 150oC with30oC of hysteresis. Once an over-temperature or over-current fault conditions is removed, the output volt-age automatically recovers.

Where PD is the power dissipated by the regula-tor and θJA is the thermal resistance from the junc-tion of the die to the ambient temperature.

n Application Information

VIN

2.7V to 5.5VSW

FBGND

IN

EN150K

150K

VOUT

1.2V

AME5254

2.2µH

COUT

10µFCER

CIN

4.7µFCER

CFWD

Figure 4: 1.2V Step-Down RegulatorCFWD: 22pF~220pF

VIN

2.7V to 5.5VSW

FBGND

IN

EN150K

100K

VOUT

1.5V

AME5254

2.2µH

COUT10µFCER

CIN

4.7µFCER

CFWD


VIN

2.7V to 5.5VSW

FBGND

IN

EN150K

47.3K

VOUT

2.5V

AME5254

2.2µH

COUT

10µFCER

CIN

4.7µFCER

CFWD


CFWD

VIN

3.6V to 5.5VSW

FBGND

IN

EN150K

33.3K

VOUT

3.3V

AME5254

2.2µH

COUT10µFCER

CIN

4.7µFCER


AME

10

AME5254

Rev. A.01


PC Board Layout ChecklistWhen laying out the printed circuit board, the following checklist should be used to ensure proper operation of the

AME5254. These items are also illustrated graphically in Figure 8. Check the following in your layout:

1. The power traces, consisting of the GND trace, the SW trace and the VIN trace should be kept short, direct and wide.

2. Does the VFB pin connect directly to the feedback resistors? The resistive divider R2/R1 must be connected between the (+) plate of COUT and ground.

3. Does the (+) plate of CIN connect to VIN as closely as possible? This capacitor provides the AC current to the internal power MOSFETs.

4. Keep the switching node, SW, away from the sensitive VFB node.

5. Keep the (-) plates of CIN and COUT as close as possible.

Figure 8 : AME5254 Adjustable VoltageRegulator Layout Diagram

SW

GND

IN

EN

VOUTL1

+

+

-

-

AME5254

VIN

COUT

CIN

FB

CFWD: 22pF~220pF

CFWD

R1

R2

AME

11

AME5254

Rev. A.01

C


i e

n Characterization CurveEfficiency vs. Output Current Efficiency vs. Output Current

Efficiency vs. Output Current Efficiency vs. Output Current

Efficiency vs. Output Current Efficiency vs. Output Current

10000

Eff

icie

ncy

(%)

Output Current (mA)

100

10

20

30

40

50

60

70

80

90

00.1 1 10 100 1000

VIN = 3.6V

VOUT = 3.3V COUT = 10µF L = 2.2µH

Eff

icie

ncy

(%)

Output Current (mA)

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100 1000 10000

VIN = 4.2V


Eff

icie

ncy

(%)

Output Current (mA)

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100 1000 10000

VIN = 5.5V


Output Current (mA)E

ffic

ien

cy (%

)30

40

50

60

70

80

90

100

0.1 1 10 100 1000 10000

VIN = 3.6V


Eff

icie

ncy

(%)

Output Current (mA)

30

40

50

60

70

80

90

100

0.1 1 10 100 1000 10000

VIN = 4.2V


Output Current (mA)

Effic

ienc

y (%

)

30

40

50

60

70

80

90

100

0.1 1 10 100 1000 10000

VIN = 5.5V


AME

12

AME5254

Rev. A.01


n Characterization Curve

Reference Voltage vs. Temperature Frequency vs. Temperature

Frequency vs. Supply Voltage Output Voltage vs. Output Current

Current Limit vs. Temperature Current Limit vs. Temperature

1.31.41.51.61.71.81.92.02.12.22.32.42.52.62.72.82.93.0

-40 -25 -10 +5 +20 +35 +50 +65 +80 +95 +110 +125

Cu

rren

t Lim

it(A

)

Temperature (oC)

VIN = 3.3VVOUT = 1.2V

1.31.41.51.61.71.81.92.02.12.22.32.42.52.62.72.82.93.0

-40 -25 -10 +5 +20 +35 +50 +65 +80 +95 +110 +125

Cur

ren

t Lim

it(A

)

Temperature (oC)

VIN = 3.6VVOUT = 1.2V

Temperature (°C)

Ref

eren

ce V

olta

ge

(V)

0.580

0.585

0.590

0.595

0.600

0.605

0.610

0.615

0.620

0 25 50 75 100 125-50 -25

VIN = 3.6V

Temperature (°C)F

requ

ency

(M

Hz)

1.10

1.15

1.20

1.25

1.30

1.35

1.40

1.45

1.50

1.55

1.60

1.65

1.70

-50 -25 0 25 50 75 100 125

VIN = 3.6V

VIN (V)

Freq

uen

cy (M

Hz)

1.10

1.15

1.20

1.25

1.30

1.35

1.40

1.45

1.50

1.55

1.60

1.65

1.70

2.5 3.0 3.5 4.0 4.5 5.0 5.51.75

1.76

1.77

1.78

1.79

1.80

1.81

1.82

1.83

1.84

1.85

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Output Current (mA)

Ou

tput

Vol

tage

(V

)

VOUT = 1.8V

AME

13

AME5254

Rev. A.01

C


i e

n Characterization Curve

Power Off from EN

Load Step Load Step

VIN = 3.6VVOUT = 1.8VIOUT = 0.5A~2A~0.5A

1)VOUT = 200mV/div

2)IOUT = 1A/div

Load Step

VIN = 3.6VVOUT = 1.8VIOUT = 0A~2A~0A

1) VOUT = 200mV/div

2) IOUT = 1A/div

VIN = 3.6VVOUT = 1.8VIOUT = 0.2A~2A~0.2A

1) VOUT = 200mV/div

2) IOUT = 1A/div

VIN=3.6VVOUT=1.8VIOUT=2A

1) EN=2V/div2) VOUT=2V/div3) IL=1A/div

1

2

1

2

1

2

40µµµµµS/Div

40µµµµµS/Div 40µµµµµS/Div

1

2

3

200µµµµS/Div

AME

14

AME5254

Rev. A.01


n Tape and Reel Dimension

SOT-25

Carrier Tape, Number of Components Per Reel and Reel Size

Package Carrier Width (W) Pitch (P) Pitch (P0) Part Per Full Reel Reel Size

SOT-25 8.0±0.1 mm 4.0±0.1 mm 4.0±0.1 mm 3000pcs 180±1 mm

W

P0

AME AME

PIN 1

P

Package Carrier Width (W) Pitch (P) Pitch (P0) Part Per Full Reel Reel Size

SOT-26 8.0±0.1 mm 4.0±0.1 mm 4.0±0.1 mm 3000pcs 180±1 mm

Carrier Tape, Number of Components Per Reel and Reel Size

P

PIN 1

W

P0

AME AME

SOT-26

AME

15

AME5254

Rev. A.01

C


i e

n Package Dimension (Contd.)

SOT-25

Top View Side View

D

S1

e

EH

Front View

A1

b

A

L

��

PIN 1

n Lead Pattern

Note:

1. Lead pattern unit description:

BSC: Basic. Represents theoretical exact dimension

or dimension target.

2. Dimensions in Millimeters.

3. General tolerance +0.05mm unless otherwise specified.

0.70 BSC

1.00

BSC

0.95 BSC 0.95 BSC

1.90 BSC

2.40

BSC

AME

16

AME5254

Rev. A.01


n Package Dimension

SOT-26

Side View

L

��

Top View

S1

De

EH

Front View

b

AA

1

PIN 1

Life Support Policy:These products of AME, Inc. are not authorized for use as critical components in life-support

devices or systems, without the express written approval of the presidentof AME, Inc.

AME, Inc. reserves the right to make changes in the circuitry and specifications of its devices andadvises its customers to obtain the latest version of relevant information.

AME, Inc. , July 2017Document: A035A-DS5254-A.01

Corporate HeadquarterAME, Inc.8F, 12, WenHu St., Nei Hu Dist.Taipei, Taiwan. 114Tel: 886 2 2627-8687Fax: 886 2 2659-2989

www.ame.com.twE-Mail: [email protected]

ame · ame 5 ame5254 rev. a.01 c 1.5mhz, 2a, synchronous ste p-down dc/dc converter ie n absolute m...

Documents