AP3409/A

Document number: DS36789 Rev. 2 - 2

3 of 11

www.diodes.com

January 2014

© Diodes Incorporated

AP3409/A

A Product Line of

Diodes Incorporated

Pin Descriptions

Pin Number

Pin Name

Function

AP3409

AP3409A

1

1

SHDN/RT

Oscillator resistor input. Connect a resistor to GND from this pin to set the

2

2

GND

Signal ground. All small-signal ground, such as the compensation

components and exposed pad should be connected to this, which in turn

connects to PGND at one point

3, 4

3, 4

SW

Internal power switch output. Connect this pin with one terminal of the

inductor

5

5

PGND

6, 7

6

PVDD

Power Input Supply. Decouple this pin to PGND with a capacitor

8

7

VDD

Signal input supply. Decouple this pin to GND with a capacitor. Normally

–

8

PGOOD

Power good indicator. This pin is open-drain logic output that is pulled to

ground when the output voltage is not within ±12.5% of regulation point

9

9

FB

Feedback voltage. This pin is the inverting input of internal error amplifier.

It senses the converter output voltage through an external resistor

divider. The internal reference voltage is 0.8V, which determines the

output voltage through the resistor divider

10

10

COMP

Compensation input. This pin is the output of internal error amplifier.

Connect external compensation elements to this pin to stabilize the

control loop

Functional Block Diagram

SD

Oscillator

SUM

CS

0.8V

EA

OCP

Control

Logic

OTP

UVLO

0.4V

SHDN/RT

PVDD

SW

GND

PGND

VDD

FB

COMP

1

2

10

3, 4

5

6, 7

8

9

PWM

Clamp

SS

DC

Functional Block Diagram of AP3409