July 2000

Adjustable Output Low Voltage Boost Regulator

BLOCK DIAGRAM

GENERAL DESCRIPTION

The ML4761 is a boost regulator designed for DC to DC

conversion in 1 to 3 cell battery powered systems. The

combination of BiCMOS process technology, internal

synchronous rectification, variable frequency operation,

and low supply current make the ML4761 ideal for 1 cell

applications. The ML4761 is capable of start-up with input

voltages as low as 1V, and the output voltage can be set

anywhere between 2.5V and 6V by an external resistor

divider connected to the SENSE pin.

An integrated synchronous rectifier eliminates the need for

an external Schottky diode and provides a lower forward

voltage drop, resulting in higher conversion efficiency. In

addition, low quiescent battery current and variable

frequency operation result in high efficiency even at light

loads. The ML4761 requires a minimum number of

external components to build a very small adjustable

regulator circuit capable of achieving conversion

efficiencies in excess of 90%.

The circuit also contains a RESET output which goes low

when the IC can no longer function due to low input

voltage (UVLO).

FEATURES

s

Guaranteed full load start-up and operation at 1V input

s

Pulse Frequency Modulation and Internal Synchronous

Rectification for high efficiency

s

Minimum external components

s

Low ON resistance internal switching FETs

s

Micropower operation

s

Adjustable output voltage (2.5V to 6V)

1

+

–

+

5

8

3

1

2

6

L1

VREF

SENSE

GND

UVLO

RESET

+

–

PWR

GND

*OPTIONAL

TO MICROPROCESSOR

7

–

R1

R2

4

BOOST

CONTROL

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