July 2000

ML4790

*

Adjustable Output, Low Ripple Boost Regulator

FEATURING

Extended

Commercial

Temperature

Range

–20°C

to 70°C

for Portable

Handheld

Equipment

BLOCK DIAGRAM

1

GENERAL DESCRIPTION

The ML4790 is a high efficiency, PFM (Pulse Frequency

Modulation), boost switching regulator connected in

series with an integrated LDO (Low Dropout Regulator)

that incorporates “Silent Switcher™” technology. This

technique incorporates a patented tracking scheme to

minimize the voltage drop across the LDO and increase

the total efficiency of the regulator beyond that which can

be obtained by using a discrete external LDO regulator.

The ML4790 is designed to convert single or multiple cell

battery inputs to regulated output voltages for integrated

circuits and is ideal for portable communications

equipment that cannot tolerate the output voltage ripple

normally associated with switching regulators.

An integrated synchronous rectifier eliminates the need for

an external Schottky diode and provides a lower forward

voltage drop, resulting in higher conversion efficiency.

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

FEATURES

s

Incorporates “Silent Switcher™” technology to deliver

very low output voltage ripple (typically 5mV)

s

Guaranteed full load start-up and operation at 1.0V

input and low operating quiescent current (<100

µA)

for extended battery life

s

Pulse Frequency Modulation and internal synchronous

rectification for high efficiency

s

Minimum external components

s

Low ON resistance internal switching MOSFETs

s

Adjustable output voltage (2.5V to 5.5V)

Patent Pending

*Optional

BOOST

CONTROL

4

8

2

1

6

L1

SHDN

GND

FEEDBACK

+

–

PWR

GND

FROM

POWER

MANAGEMENT

7

LDO

CONTROL

5

C2

3

SENSE