July 2000

3.3V Output DC–DC Step-Down Converter

1

GENERAL DESCRIPTION

The ML4866 is a high efficiency pulse width modulated

(PWM) buck regulator designed for use in 5V systems or

portable equipment that need a compact, efficienct 3.3V

supply. It has a switching frequency of 120kHz and uses

synchronous rectification to optimize power conversion

efficiency. Unlike other solutions, the ML4866 requires no

external diodes or FETs.

The ML4866 can provide up to 500mA of output current,

and operates over an input voltage range of 3.5V to 6.5V

(3 to 4 cells or a 5 VDC supply). A complete switched

mode power converter can be quickly and easily

implemented with few external components. Thanks to a

built-in autoburst mode, power conversion efficiency of

this DC–DC converter can exceed 90% over more than 2

decades of output load current.

Stability and fast loop response are provided by current

programming and a current sense circuit. The ML4866

also has a SHDN pin for use in systems which have power

management control. Undervoltage lockout and soft start

are also built in.

BLOCK DIAGRAM

FEATURES

s

High power conversion efficiency over 2 decades of

load current

s

No external FETs or diodes; minimum external

components

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3.5V to 6.5V input voltage range

s

Significantly extends battery life over linear regulator

based solutions

s

Micropower operation

s

Low shutdown mode quiescent current

VREF

VIN

5

SHDN

6

VREF

3

BURST

4

COMP

2

GND

8

VOUT

1

VL

7

–

+

REFERENCE

UVLO/

SHUTDOWN

CURRENT

SENSE

–

+

ERROR

AMPLIFIER

BUCK

CONTROL

OSC

SLOPE

COMPENSATION

BURST

(* Indicates Part is End Of Life as of July 1, 2000)