AME 2A, 300KHz ~ 2MHz Synchronous Rectif ied Ste p-Down … · 2012. 8. 6. · AME 1 AME5282 Rev. A.02 2A, 300KHz ~ 2MHz Synchronous Rectif ied Ste p-Down Converter n Typical Application

AME

1

AME5282

Rev. A.02

2A, 300KHz ~ 2MHz SynchronousRectified Step-Down Converter

n Typical ApplicationThe AME5282 is a Synchronous Rectified Step-Down

Converter with internal power MOSFETs. It achieves 2Acontinuous output current over a wide switching frequencyrange with excellent load and line regulation.

Current mode operation provides fast transient responseand eases of loop stabilization. Internal soft-start mini-mizes the inrush supply current at startup. The circuitprotection includes cycle-by-cycle current limiting, out-put short circuit frequency protection and thermal shut-down. In shutdown mode, the regulator reduces the cur-rent less than 1µA of supply current.

This device is available in SOP-8/PP ,DFN-8 packagewith exposed pad for low thermal resistance.

n General Description

n Applications

Figure 1. 3.3V at 2A Step-Down Regulators.

Figure 2. 1V at 2A Step-Down Regulators.

l TVl Distributed Power Systemsl Pre-Regulator for Linear Regulatorsl Digital Cameras

n Features

l 2A Output Currentl Stable with Low ESR Output Ceramic

Capacitorsl Pre-Regulator for Linear Regulatorsl Up to 95% Efficiencyl Less than 1µA Shutdown Currentl Wide Switching Frequency Range from

300KHz~2MHzl Thermal Protectionl Cycle-by-Cycle Over Current Protectionl Output Adjustable from 0.8V to VINl Short Circuit Protectionl Green Products Meet RoHS Standards

AME5282

SW

RFREQ18KΩ

ONOFF

VIN5V

CIN10µF

C2Optional

C1680pF

R325KΩ

IN

EN

COMP

GNDFREQ

R175KΩ

R224KΩ

COUT22µF

FB

VOUT3.3V

L 2.2µH

AME5282

SW

RFREQ18KΩ

ONOFF

VIN2.5V~5V

CIN10µF

C2Optional

C1680pF

R38.2KΩ

IN

EN

COMP

GNDFREQ

R16KΩ

R224KΩ

COUT22µF

FB

VOUT1V

L 1.5µH

AME

2

2A, 300KHz ~ 2MHz SynchronousRectified Step-Down ConverterAME5282

Rev. A.02

n Functional Block Diagram

SOP-8/PPTop View

AME5282-AZAADJ

1. COMP

2. GND

3. EN

4. IN

5. SW

6. SW

7. FREQ

8. FB

9. GND (Exposed Pad)

* Die Attach: Conductive Epoxy

Note. Connect exposed pad (heat sink on the back) to GND.

DFN-8C(3mmx3mmx0.75mm)

Top View

AME5282-AVAADJ

1. COMP

2. GND

3. EN

4. IN

5. SW

6. SW

7. FREQ

8. FB

9. GND (Exposed Pad)

* Die Attach: Conductive Epoxy

1 32 4

AME5282

5678

9

8 7 6

1 2 3 4

AME5282

5

9

n Pin Configuration

OTP

SOFTSTART

++-

0.8VVREF

SLOPE

OSC

ENABLE UVLO

PWM

IN

SW

SW

PGND

EN

FREQ

COMP

GND

FB

-

+

EA

CURRENTSENSE

IRCMP

-+

LOGICDRIVER

CURRENTLIMIT

Short circuit

AME

3

AME5282

Rev. A.02


n Pin Description

Pin No. Pin Name Pin Description

1 COMP

Compensation Node. COMP is used to compensate the regulation control loop.Connect a series RC network from COMP to GND to compensate the regulationcontrol loop. In some cases, an additional capacitor from COMP to GND isrequired.

2 GND Ground. Connect the exposed pad to GND.

3 EN Enable. Pull EN below 0.4V to shut down the regulator.

4 INPower Input. IN supplies the power to the IC, as well as the step-down converterswitches. Bypass IN to GND with a suitable large capacitor to eliminate noise onthe input to the IC.

5, 6 SW Power Switching Output. SW is the switching node that supplies power to theoutput. Connect the output LC filter from SW to the output load.

7 FREQ Frequency Adjust Pin. Add a resistor from this pin to ground determines theswitching frequency.

8 FBFeedback Input. FB senses the output voltage to regulate that voltage. Drive FBwith a resistive voltage divider from the output voltage. The feedback referencevoltage is 0.8V.

9 GND Ground. Connect the exposed pad to GND.

AME

4


Rev. A.02

n Ordering Information

AME5282 - x x x xxx

Pin Configuration

Package Type

Number of Pins

Output Voltage

A 1. COMP Z: SOP/PP A: 8 ADJ: Adjustable(SOP-8/PP) 2. GND V: DFN(DFN-8C) 3. EN

4. IN5. SW6. SW7. FREQ8. FB9. GND

Pin Configuration Package Type Number of Pins Output Voltage

AME

5

AME5282

Rev. A.02


n Absolute Maximum Ratings

n Recommended Operating Conditions

Parameter Symbol Maximum Unit

Supply Voltage VIN 6 V

Switch Voltage VSW -0.7V to VIN+0.7V V

EN, FB, COMP, FREQ to GND -0.3V to VIN+0.3V V

HBM 2 kV

MM 200 VESD Classification

Parameter Symbol Rating Unit

Ambient Temperature Range TA -40 to +85

Junction Temperature Range TJ -40 to +125

Storage Temperature Range TSTG -65 to +150

oC

AME

6


Rev. A.02

n Thermal Information

* Measure θJC on backside center of Exposed Pad.** MIL-STD-202G 210F

Parameter Package Die Attach Symbol Maximum Unit

SOP-8/PP 15

DFN-8C 8.2

SOP-8/PP 75

DFN-8C 70

SOP-8/PP 1.333

DFN-8C 1.429

Maximum Junction Temperature 150 oC

260 oC

oC / W

W

Lead Temperature (Soldering,10Sec)**

PD

θJA

θJC

Conductive Epoxy Thermal Resistance (Junction to Ambient)

Thermal Resistance* (Junction to Case)

Internal Power Dissipation

AME

7

AME5282

Rev. A.02


n Electrical Specifications

VIN=5V, TA=25oC, unless otherwise noted.

Parameter Symbol Test Condition Min Typ Max Units

Input Voltage VIN 2.5 5.5 V

Input UVLO VUVLO 2.3 V

Quiescent Current IQVEN=5V, VFB=0.7V

(No Switching)600 µA

Shutdown Current ISHDN VEN=0V 1 µA

Feedback Voltage VFB 0.784 0.8 0.816 V

Feedback Current IFB -50 50 nA

Load Regulation REGLOAD 0A

AME

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Rev. A.02

Normal Operation

The AME5282 uses a user adjustable frequency, cur-rent mode step-down architecture with internal MOSFETswitch. During normal operation, the internal high-side(PMOS) switch is turned on each cycle when the oscilla-tor sets the SR latch, and turned off when the compara-tor resets the SR latch. The peak inductor current atwhich comparator resets the SR latch is controlled bythe output of error amplifier EA. While the high-side switchis off, the low-side switch turns on until either the induc-tor current starts to reverse or the beginning of the nextswitching cycle.

Dropout Operation

The output voltage is dropped from the input supply forthe voltage which across the high-side switch. As theinput supply voltage decreases to a value approachingthe output voltage, the duty cycle increases toward themaximum on-time. Further reduction of the supply volt-age forces the high-side switch to remain on for morethan one cycle until it reaches 100% duty cycle.

Soft-Start

The AME5282 has a built-in digital soft-start to controlthe output voltage rise and limit the current surge at thestart-up.

When the internal soft-start begins, and count 896switching cycles, soft start is complete, the converterenters steady state operation.

Hiccup Mode

During hiccup mode, the AME5282 disables the high-side MOSFET and begins a cool down period of 8320switching cycles. At the conclusion of this cool downperiod, the regulator performs an internal 896 cycle softstart identical to the soft start at turn-on.

n Detailed Description Under Voltage Protection

Under Voltage Protection will activate once the feed-back voltage falls below 0.4V, the operating frequency isswitched to 1/10 of normal switching frequency and afterfour-times hiccup mode counted, the internal high-sidepower switch will be turned off,and latched. Unless Re-start the power supply.

Over Temperature Protection

In most applications the AME5282 does not dissipatemuch heat due to high efficiency. But, in applicationswhere the AME5282 is running at high ambient tempera-ture with low supply voltage and high duty cycles, suchas in dropout, the heat dissipated may exceed the maxi-mum junction temperature of the part. If the junctiontemperature reaches approximately 160oC, the internalhigh-side power switch will be turned off and the SWswitch will become high impedance.

Inductor Selection

For most applications, the value of the inductor will fallin the range of 2.2µH to 4.7µH. Its value is chosen basedon the desired ripple current. Large value inductors lowerripple current and small value inductors result in higherripple currents. Higher V IN or VOUT also increase the ripplecurrent ∆IL:

−

×=∆

IN

OUTTOUL V

VV

LfI 1

1

AME

9

AME5282

Rev. A.02


A reasonable inductor current ripple is usually set as 1/3 to 1/5 of maximum out current. The DC current ratingof the inductor should be at least equal to the maximumload current plus half the ripple current to prevent coresaturation. For better efficiency, choose a low DCR in-ductor.

Capacitor Selection

In continuous mode, the source current of the topMOSFET is a square wave of duty cycle VOUT/VIN. Toprevent large voltage transients, a low ESR input capaci-tor sized for maximum RMS current must be used. Themaximum RMS capacitor current is given by:

CIN requires IRMS

This formula has a maximum at V IN=2V OUT ,whereIRMS=IOUT/2. For simplification, use an input capaci-tor with a RMS current rating greater than half of themaximum load current.

The selection of COUT is driven by the required effectiveseries resistance (ESR). Typically, once the ESR require-ment for COUT has been met, the RMS current rating gen-erally far exceeds the IRIPPLE(P-P) requirement. The outputripple ∆VOUT is determined by:

∆VOUT

For a fixed output voltage, the output ripple is highestatmaximum input voltage since ∆IL increases with input volt-age.

When choosing the input and output ceramic capaci-tors, choose the X5R or X7R dielectric formulations. Thesedielectrics have the best temperature and voltage char-acteristics of all the ceramics for given value and size.

Output Voltage Programming

The output voltage of the AME5282 is set by a resistivedivider according to the following formula:

Loop Compensation

The AME5282 employs peak current mode control foreasy use and fast transient response. Peak current modecontrol eliminates the double pole effect of the output LCfilter. It greatly simplifies the compensation loop design.

With peak current mode control, the buck powerstagecan be simplified to be a one-pole and one-zero sys-tem in frequency domain. The pole can be calculated by:

The zero is a ESR zero due to output capacitor and itsESR. It can be calculated by:

.21

18.0 VoltRR

VOUT

+×=

LOUTP RC

f××

=π2

11

COUTOUTZ ESRC

f××

=π2

11

+∆≅

OUTL fC

ESRI8

1

( )IN

OUTINOUTOMAX V

VVVI

−≅

AME

10


Rev. A.02

Where COUT is the output capacitor, RL is load resis-tance; ESRCOUT is the equivalent series resistance ofoutput capacitor.

The compensation design is to shape the converter closeloop transfer function to get desired gain and phase. Formost cases, a series capacitor and resistor network con-nected to the COMP pin sets the pole-zero and is ad-equate for a stable high-bandwidth control loop.

In the AME5282, FB pin and COMP pin are the invert-ing input and the output of internal transconductance er-ror amplifier (EA). A series R3 and C1 compensation net-work connected to COMP pin provides one pole and onezero: for R3

AME

11

AME5282

Rev. A.02


Other losses including CIN and COUT ESR dissipativelosses and inductor core losses generally account forless than 2% total additional loss.

Thermal Considerations

In most application the AME5282 does not dissipatemuch heat due to its high efficiency. But, in applicationswhere the AME5282 is running at high ambient tempera-ture with low supply voltage and high duty cycles, suchas in dropout, the heat dissipated may exceed the maxi-mum junction temperature of the part. If the junctiontemperature reaches approximately 160oC, both powerswitches will be turned off and the SW switch will be-come high impedance.

AME

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Rev. A.02

n Typical Operating Circuit

Table 1. Recommended Components Selectin for fsw = 2MHz

Figure 3. AME5282 Regulators Layout Diagram

VIN

COMP FB

FREQ

SW

VOUT

GND

R3

C1

CIN

R2

R1

RFREQ

L1

COUT

C IN must be placed between V IN and GND as close as possible

SW pad should beconnected together to Inductor by wide and shorttrace, keep sensitivecomponents away from this trace.

GND

1

2

3

4 5

6

7

8

VIN

GND

SW

SW

VOUT

Connect the FB pin directly to feedback resistors.

The ground area must provide adequate heat dissipating area to the thermal pad andusing multiple vias to help thermal dissipation.

Place the input and output capacitors as close to the IC as possible

EN

VOUT(V) CIN(µF) R1(KΩ) R2(KΩ) R3(KΩ) C1(pF) L(µH) COUT(µF)

3.3 10 75 24 25 680 2.2 22

2.5 10 51 24 20 680 2.2 221.8 10 30 24 15 680 1.5 22

1.5 10 21 24 13 680 1.5 22

1.2 10 12 24 11 680 1.5 22

1 10 6 24 8.2 680 1.5 22

AME5282

SW

ROSC

Chip Enable

VIN2.5V to 5V

CIN10uF

CC2Optional

CC

RC

IN

EN

COMP

GND

FREQ

R1

R2

COUT

FB

VOUTL4

3

1

2

5 , 6

8

7

GND 9( Exposed pad )

AME

13

AME5282

Rev. A.02


n Characterization Curve

Efficiency vs. Output Current Efficiency vs. Output Current

Efficiency vs. Output Current Efficiency vs. Output Current

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000

Output Current (mA)

Eff

icie

ncy

(%) VOUT=3.3V VOUT=2.5V

VOUT=1.8V

VOUT=1.2V

VOUT=1V

VIN = 5V RF = 18K

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000

Output Current (mA)

Eff

icie

ncy

(%) VOUT=3.3V

VOUT=2.5V VOUT=1.8V VOUT=1.2V

VOUT=1.0V

V IN = 5V RF = 30K

100

Output Current (mA)

Eff

icie

ncy

(%)

0

10

20

30

40

50

60

70

80

90

0 500 1000 1500 2000

VOUT=1.0VVOUT =1.2V

VOUT=1.8VVOUT=2.5V

VOUT=3.3V

VIN = 5V RF = 47K

Output Current (mA)

Eff

icie

ncy

(%)

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000

VOUT=1.0V

VOUT=1.2V

VOUT=1.8V

VOUT=2.5VVOUT=3.3V

VIN = 5V RF = NC

AME

14


Rev. A.02

n Characterization Curve (Contd.)

Load Step Load Step

VIN= 3.3V VOUT= 1.0V IL= 1A to 2A


Load Step Load Step



Time (200µSec/DIV)

IL1A/DIV

VOUT 200mV/DIV

Time (400µSec/DIV)

IL1A/DIV

VOUT 200mV/DIV

Time (200µSec/DIV)

IL1A/DIV

VOUT 100mV/DIV

Time (400µSec/DIV)

IL1A/DIV

VOUT 100mV/DIV

AME

15

AME5282

Rev. A.02


2

1

3

4

2.0mS / div


Power ON from VIN Power off from VIN

1) VIN= 5V/div2) Vsw= 5V/div3) VOUT= 1V/div4) IL= 1A/div

1) VIN= 5V/div2) Vsw= 5V/div3) VOUT= 1V/div4) IL= 1A/div

Start-Up from EN Power Off from EN

1) EN= 5V/div2) VSW= 5V/div3) VOUT= 1V/div4) IL = 1A/div

1) EN= 5V/div2) VSW= 5V/div3) VOUT= 1V/div4) IL = 1A/div

1

2

3

4

400uS / div

1

3

2

4

400uS / div

2.0mS / div

2

1

3

4

AME

16


Rev. A.02

Steady State Test Steady State Test

VIN= 5VVOUT= 1.1V IOUT = 2A

VIN= 5VVOUT= 3.3VIOUT = 2A

1) VIN= 10mV/div2) VSW= 2V/div

1) VIN= 10mV/div2) VSW= 2V/div


VFB vs. Temperature Frequency vs. Temperature

2

1

400nS / DIV

VIN= 5V VOUT= 1.1V IOUT= 2A

400nS / DIV

2

1

VIN= 5V VOUT= 3.3V IOUT= 2A

0.77

0.78

0.79

0.80

0.81

0.82

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

Temperature (°C)

VFB

(V)

150

200

250

300

350

400

450

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

Temperature (°C)

Freq

uen

cy

(KH

z)

VIN = 5V

AME

17

AME5282

Rev. A.02



Frequency vs. Supply Voltage Frequency vs. Output Current

Short Circuit TestShort Circuit Test

150

200

250

300

350

400

450

3.5 4 4.5 5 5.5

Input Voltage (V)

Freq

uenc

y (K

Hz)

VOUT = 3.3V

200

210

220

230

240

250

260

270

280

290

300

100 300 500 700 900 1100 1300 1500 1700 1900

IOUT (mA)

Freq

uenc

y (K

Hz)

VIN=5.0VVOUT = 3.3V

IOUT2A/DIV

VOUT 1V/DIV

Time (100ms/DIV)

VIN=5.0VVOUT = 1V

IOUT2A/DIV

VOUT 2V/DIV

Time (100ms/DIV)

VIN=5.0VVOUT = 3.3V

AME

18


Rev. A.02

n Tape and Reel Dimension


W

P

PIN 1

AM

E

AM

E

Carrier Tape, Number of Components Per Reel and Reel Size

SOP-8/PP

Carrier Tape, Number of Components Per Reel and Reel Size

PIN 1

W

P

AME

AM

E

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

DFN-8C(3x3x0.75mm) 12.0±0.1 mm 4.0±0.1 mm 3000pcs 330±1 mm

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

SOP-8/PP 12.0±0.1 mm 4.0±0.1 mm 2500pcs 330±1 mm

AME

19

AME5282

Rev. A.02


n Package Dimension

SOP-8/PP

b e

EE2

C

FRONT VIEW

SIDE VIEWTOP VIEWD1

E1

L1

DA

1

AA2

?

PIN 1

MIN MAX MIN MAX

A 1.350 1.750 0.053 0.069

A1 0.000 0.150 0.000 0.006

A2 1.350 1.600 0.053 0.063

C 0.100 0.250 0.004 0.010

E 3.750 4.150 0.148 0.163E1 5.700 6.300 0.224 0.248

L1 0.300 1.270 0.012 0.050

b 0.310 0.510 0.012 0.020

D 4.720 5.120 0.186 0.202

eθ 0o 8o 0o 8o

E2 2.150 2.513 0.085 0.099

D1 2.150 3.402 0.085 0.134

1.270 BSC 0.050 BSC

SYMBOLSMILLIMETERS INCHES

AME

20


Rev. A.02

n Package Dimension (Contd.)


MIN MAX MIN MAX

A 0.700 0.800 0.028 0.031

D 2.900 3.100 0.114 0.122

E 2.900 3.100 0.114 0.122

e 0.600 0.700 0.024 0.028

D1 2.200 2.400 0.087 0.094

E1 1.400 1.600 0.055 0.063

b 0.180 0.320 0.007 0.013

L 0.375 0.575 0.015 0.023

G 0.153 0.253 0.006 0.010

G1 0.000 0.050 0.000 0.002

SYMBOLSMILLIMETERS INCHES

TOP VIEW

BOTTOM VIEW

REAR VIEW

eD

E

A GG1

b

L

E1

D1

PIN 1 IDENTIFICATION

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. , JuIy 2012Document: TU003-DS5282-A.02

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

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

Documents

AME 2A, 300KHz ~ 2MHz Synchronous Rectif ied Ste p-Down … · 2012. 8. 6. · AME 1 AME5282 Rev. A.02 2A, 300KHz ~ 2MHz Synchronous Rectif ied Ste p-Down Converter n Typical Application