PWR

GND

3

1

L1

GND

2

8

REGULATION

&

SHUTDOWN

CONTROL

FROM POWER

MANAGEMENT

FEEDBACK

5

SHDN

6

BOOST

CONTROL

4

SENSE

August 2000

ML4775

Adjustable Output Low Voltage

Boost Regulator with Shutdown

1

*Optional

BLOCK DIAGRAM

GENERAL DESCRIPTION

The ML4775 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 ML4775 ideal for 1 cell

applications. The ML4775 is capable of start-up with input

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

anywhere between 2.5V and 5.5V by an external resistor

divider connected to the SENSE pin.

Unlike regulators using external Schottky diodes, the

ML4775 isolates the load from the battery when the

SHDN pin is high. This is accomplished by an integrated

synchronous rectifier which 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 ML4775 requires a minimum number of

external components to build a very small regulator circuit

capable of achieving conversion efficiencies in excess of

90%.

FEATURES

s

Guaranteed start-up and operation at 1V input

s

Pulse Frequency Modulation and Internal Synchronous

Rectification for high efficiency

s

Isolates the load from the input during shutdown

s

Minimum external components

s

Low ON resistance internal switching FETs

s

Micropower operation

s

Adjustable output voltage (2.5V to 5.5V)