ANPEC APW7057KC-TU, APW7057KC-TR Datasheet

APW7057

High Power Step-Down Synchronous DC/DC Controller

Features

••

Operates from +5V Input

•

••

0.8V Internal Reference Voltage

•

••

- ±1.5% Accuracy Over Line, Load and Temp.

••

0.8V to VCC Output Range

•

••

Full Duty Cycle Range

•

••

- 0% to 100%

••

Internal Loop Compensation

•

••

Internal Soft Start

•

••

- Typical 2ms

••

• Programmable Over-Current Protection

••

- Lossless Sensing Using MOSFET R

••

• Under-Voltage Protection

••

• Drives External N-Channel MOSFETs

••

• Shutdown Control

••

• Small SOP-8 Package

••

DS (ON)

Applications

••

• Motherboard

••

• Graphics Cards

••

• Cable or DSL Modems, Set Top Boxes

••

• DSP Supplies

••

General Description

The APW7057 is a 300kHz constant frequency voltage mode synchronous switching controller that drives external N-channel MOSFETs. When the input supply drops close to output, the upper MOSFET remains on, achieving 100% duty cycle. Internal loop compensation is optimized for fast transient response, eliminating external compensation network. The precision

0.8V reference makes this part suitable for a wide variety of low voltage applications. Soft start is internally set to 2ms, limiting the input in-rush current and preventing the output from overshoot during powering up. The APW7057 has over current and short circuit protections. Over current protection is achieved by monitoring the voltage drop across the high side MOSFET, eliminating the need for a current sensing resistor and short circuit condition is detected through the FB pin. If either fault conditions occur, the APW7057 would initiate the soft start cycle. After three cycles and if the fault condition persists, the controller will be shut down. To restart the controller , either recycle the V OSCSET pin below 1.25V.

The APW7057 can be shutdown by pulling the OCSET pin below 1.25V. In shutdown, both gate drive signals

will be low. The controller is available in a small SOP8 package.

supply or momentarily pull the

CC

••

• Memory Supplies

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• 5V Input DC-DC Regulators

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• Distributed Power Supplies

••

ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and advise customers to obtain the latest version of relevant information to verify before placing orders.

Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003

Pinouts

BOOT

UGATE

GND

LGATE

1 2

3

4

SOP-8 (Top View )

8 7

6 5

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PHASE

OCSET

FB

VCC

APW7057

Ordering and Marking Information

APW 7057

APW7057 K :

Block Diagram

VCC

UnderVoltage

Lockout

UVLO

0.5V UVP

Handling Code

Temp. Range

Package Code

APW 7057 XXXXX

Soft-Start and Fault

Logic

Shutdown

OCP

Package Code K : SO P -8 Operating Junction Tem p. Range

°

C : 0 to 70 C

Handling Code

TU : Tu b e TR : Tape & Reel

XXXXX - Date Code

OC

Comparator

I

OCSET

40uA

BOOT

OCSET

PHASE

Soft-Start

FB

-

+

Error

REF

V

0.8V

Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003

Amp lif ier

Inhibit

PW M

COMP

+

-

Oscillator

.ECKH/Figure 1.

OSC

F

300kHz

UGATE

Gate

Control

VCC

LGATE

GND

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APW7057

Typical Application

R3

R4

8.2k

C7

470pF

Q3

Shutdown

Q1: APM2014N U C Q2: APM2014N U C Q3: APM2300A A C

7

6

OCSET

APW 7057

FB

C3

1uF

5

VCC

BOOT

UGATE

PHASE

U1

LGATE

GND

3

C2: 1000uF/10V, ESR = 25m

C5: 1000uF/6.3V, ESR = 25m

1

2

8

4

1N4148

.ECKH/Figure 2.

2.2

D1

C4

0.1uF

R2

2.4k

V

IN

+

C2

1000uF x2

Q1

L1

3.3uH

C1

1uF

+

Q2

R1

5.1k

C6

0.1uF

Ω

+5V

C5

1000uF x2

V

OUT

+2.5V/10A

Absolute Maximum Ratings

Symbol Parameter Rating Unit

CC

V

BOOT

VCC Supply Voltage (VCC to GND) -0.3 ~ 7 V BOO T S upply Voltage (BOOT to GN D ) -0.3 ~ 15 V PHAS E , OC S ET to GND Input Voltage -0.3 ~ 12 V FB to GN D In p u t Volta ge -0.3 ~ VCC+0.3 V Maximum Junction Tem perature 125

STG

T

SDR

T

ESD

V

Storage Temperature -65 ~ 150 Maximum Soldering Temperature, 10 Seconds 300 Minim um ESD Rating

±2

Thermal Characteristics

Symbol Parameter Value Unit

JA

θ

Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003

Junction-to-Ambient Resistance in fre e air (S OP-8) 160

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o

kV

o

C/W

C C C

APW7057

Recommended Operating Conditions

Symbol Parameter Range Unit

VCC VCC S upply Voltage 5 ± 5% V

V

Output Voltage of the Switc hing Regulator (Note) 0.8 ~ VCC V

OUT

VIN Input Voltage of the S wit c hing Regulat or (Note) 3.3 ~ VCC V

o

C

oC

Unit

P-P

A

µ

TA Am bient Temperature 0 ~ 70 TJ Junction Temperature 0 ~ 125



Note : Refer to the typical application circuit

Electrical Characteristics

Unless otherwise specified, these specifications apply over VCC=5V, VBOOT=12V and TA= 0~70 oC. Typical values are at TA=25oC.

Symbol Parameter Test Conditions

SUPP LY CURRENT

I

VCC

I

BOOT

VCC No mina l Supp l y Current

BOOT Nominal Supply Current

UGATE and LGATE Open

UGATE Open

Under Voltage Lockout(UVLO)

Risi ng V CC Threshold 4.0 4.2 4.4 V Falli ng V CC Threshold 3.8 4.0 4.2 V

OSCILLATOR

F

Free Running Frequency 250 300 340 kHz

OSC

Ramp Upper Threshol d 2.85 V Ramp Lower Threshol d 0.95 V

Ramp Amplitude 1.9 V

V

OSC

∆

REFERENCE VOLTAGE

V

Reference Voltage 0.8 V

REF

Referenc e Volt age Accuracy

-1.5 +1.5 %

ERROR AMPLIFI ER

DC Gain 75 dB FP Fi rst P ol e F requenc y 10 Hz FZ Fi rst Zero Frequency 1 kHz

UGATE Dut y Range 0 100 %

FB Input Current

Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003

APW7057

Min Typ Max

2.1 mA

0.1

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APW7057

Electrical Characteristics (Cont.)

Unless otherwise specified, these specifications apply over VCC=5V, VBOOT=12V and TA= 0~70 oC. Typical values are at TA=25oC.

Symbol Parameter Test Conditions

PWM CONTROLLER GATE DRIVERS

UGATE Source V UGATE Sink V LGATE Source LGATE Sink V

D

T

Dead Time 50 nS

UAGTE

=1V 0.6 A

UGATE

=1V 7 .3

LGATE

=1V 0.6 A

V

LGATE

=1V 1.8

PROTECTIO N

OCSET

I

UV

OCSET Sink Current V

FB

FB Under-Voltage Level FB falling 0.5 V FB Under-Voltage

Hysteresis

OCSET

=4.5V 34 40 46

15 mV

SOFT-START AND SHUTDOWN

SS

T

Soft-Start Interval 2 mS Shutdown Threshold V OCSET Shutdown

Hysteresis

OCSET

Falling 1.25 V

20 mV

APW7057

Unit

Min Typ Max

Ω

µA

Functional Pin Description

BOOT (Pin 1)

This pin provides the supply voltage to the high side MOSFET driver. A voltage no greater than 13V can be connected to this pin as a supply to the driver. For driving logic level N-channel MOSEFT, a bootstrap circuit can be use to create a suitable driver’s supply.

UGATE (Pin 2)

This pin provides gate drive for the high-side MOSFET.

GND (Pin 3)

Signal and power ground for the IC. All voltage levels are measured with respect to this pin. Tie this pin to the ground plane through the lowest impedance connection available.

Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003

LGATE (Pin 4)

This pin provides the gate drive signal for the low side MOSFET.

VCC (Pin 5)

This is the main bias supply for the controller and its low side MOSFET driver. Must be closely decoupled to GND (Pin 3). DO NOT apply a voltage greater than 5.5V to this pin.

FB (Pin 6)

This pin is the inverting input of the error amplifier and it receives the feedback voltage from an exter-

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