AP1605

PWM/PFM Dual-mode Step-Down Switching Regulator

Anachip Corp.

www.anachip.com.tw

Rev. 1.1 Jan 18, 2005

4/6

Typical Application Circuit (Continued)

（

2） Application with Short Circuit Protection

AP 1605

+

-

CE

D1

FB

SW

1N4148 for above 5V Vin and

Schottky for below 5V Vin

0.1uF

100 uF

0.2uF

3.5M

10M

1M

100 uF

)

R

R

(1

Vref

Vo

B

A

+

×

=

=~10K

Test Circuit

A

FB

Vcc

Vss

open

open

FB

Vcc

Vss

+

-

SW

SW

PVcc

PVcc

A

FB

Vcc

Vss

+

-

+

-

V

SW

PVcc

CE

CE

CE

Function Description

PWM/PFM Control (AP1605 Series)

The AP1605 consists of DC/DC converters that employ a PWM/PFM auto-switch system.

In converters of the AP1605, the PFM mode varies in a range of duty cycle from 0% to 25%, and the PWM

mode varies in a range of duty cycle from 25% to 100% according to the load current, and yet ripple voltage

produced by the switching can easily be removed through a filter because the switching frequency remains

constant. Therefore, these converters provide a low-ripple power over broad ranges of input voltage and load

current.