Copyright

© ANPEC Electronics Corp.

Rev. A.7 - Sep., 2010

APW7085

www.anpec.com.tw

11

Pin Description

PIN

NAME

FUNCTION

1

VIN

Power Input. VIN supplies the power (4.5V to 26V) to the control circuitry, gate driver and step-down

converter switch. Connecting a ceramic bypass capacitor and a suitably large capacitor between

VIN and GND eliminates switching noise and voltage ripple on the input to the IC.

2

EN

Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the

regulator, drive it low to turn it off. Pull up with 100k

Ω resistor for automatic startup.

3

UGND

Gate driver power ground of the P-channel Power MOSFET. A linear regulator regulates a 5.5V

voltage between VIN and UGND to supply power to P-channel MOSFET gate driver. Connect a

ceramic capacitor (1

µF typ.) between VIN and UGND for noise decoupling and stability of the linear

regulator.

4

VCC

Bias input and 4.2V linear regulator’s output. This pin supplies the bias to some control circuits. The

4.2V linear regulator converts the voltage on VIN to 4.2V to supply the bias when no external 5V

power supply is connected with VCC. Connect a ceramic capacitor (1

µF typ.) between VCC and

GND for noise decoupling and stability of the linear regulator.

5

LX

Power Switching Output. LX is the Drain of the P-channel MOSFET to supply power to the output.

Connect the pin to output LC filter.

6

COMP

Output of error amplifier. Connect a series RC network from COMP to GND to compensate the

regulation control loop. In some cases, an additional capacitor from COMP to GND is required for

noise decoupling.

7

FB

Feedback Input. The IC senses feedback voltage via FB and regulate the voltage at 0.8V.

Connecting FB with a resistor-divider from the output set the output voltage in the range from 0.8V

8

GND

Power and Signal Ground.

Block Diagram

LX

Gate

Control

V

REF

0.8V

Soft-Start

and

Fault Logic

Error

Amplifier

FB

Inhibit

70%V

REF

UVP

GND

POR

Soft-Start

4.2V Regulator

and

Power-On-Reset

VCC

VCC

Enable

Current Sense

Amplifier

EN

COMP

Oscillator

380kHz

Slope

Compensation

Current

Compartor

0.8V

UGND

VIN

Over-

Temperature

Protection

Current

Limit

VIN

FB

2.5V

ENOK

UG

Gate

Driver

Linear

Regulator