Preliminary Data

This is preliminary information on a new product now in development or undergoing evaluation.

Details are subject to change without notice.

Rev 1

September 2005

1/16

16

PM6685

DUAL STEP-DOWN CONTROLLER WITH AUXILARY VOLTAGES

FOR NOTEBOOK SYSTEM POWER

Features

■

CONSTANT ON TIME TOPOLOGY ALLOWS

VERY FAST LOAD TRANSIENTS

■

6V TO 28V INPUT VOLTAGE RANGE

■

FIXED 5V-3.3V OUTPUT VOLTAGES

■

5V AND 3.3V ALWAYS VOLTAGES

AVAILABLE DELIVER 100mA PEAK

CURRENT

■

1.23V

AVAILABLE

■

■

ACCURATE CURRENT SENSE WITH

■

NEGATIVE CURRENT LIMIT

■

SOFT START INTERNALLY FIXED AT 2ms

■

SOFT OFF FOR OUTPUT DISCHARGE

■

LATCHED OVP AND UVP

■

SELECTABLE PULSE SKIPPING AT LIGHT

LOADS

■

SELECTABLE MINIMUM FREQUECY

(25kHz) IN PULSE SKIP MODE

■

4 mW MAXIMUM QUIESCENT POWER

■

INDIPENDENT POWER GOOD SIGNALs

■

OUTPUT VOLTAGE RIPPLE

COMPENSATION

Description

PM6685

is

a

dual

step-down

controller

specifically designed to provide extremely high

efficiency

conversion,

with

lossless

current

sensing

technique.

The

constant

on-time

architecture assures fast load transient response

and the embedded voltage feed-forward provides

nearly constant switching frequency operation. An

embedded integrator control loop compensates

the DC voltage error due to the output ripple.

Pulse skipping technique increases efficiency at

very light load. Moreover a minimum switching

frequency of 25kHz is selectable to avoid audio

noise issues. The PM6685 provides a selectable

switching frequency, allowing either 200kHz/

300kHz,

300kHz/400Khz

or

400kHz/500kHz

operation of the 5V/3.3V switching sections...

Applications

■

NOTEBOOK COMPUTERS

■

TABLET PC OR SLATES

■

MOBILE SYSTEM POWER SUPPLY

■

3-4 CELLS Li+ BATTERY POWERED

DEVICES

VFQFPN-32 5X5

www.st.com

Order codes

Part number

Marking

Package

Packing

PM6685

PM6685

VFQFPN-32 5X5

TAPE & REEL