July 2000

ML4875

*

Low Voltage Boost Regulator with Shutdown

1

BLOCK DIAGRAM

+

–

PWR

GND

3

1

L1

GND

7

2

8

REGULATION

&

SHUTDOWN

CONTROL

REF

4

FROM POWER

MANAGEMENT

FEEDBACK

5

DETECT

SHDN

6

BOOST

CONTROL

RESET

5V

GENERAL DESCRIPTION

The ML4875 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 ML4875 ideal for 1 cell

applications. The ML4875 is capable of start-up with input

voltages as low as 1V and is available in 5V, 3.3V, and 3V

output versions with an output voltage accuracy of ±3%.

Unlike regulators using external Schottky diodes, the

ML4875 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 ML4875 requires only one inductor and two

capacitors to build a very small regulator circuit capable

of achieving conversion efficiencies in excess of 90%.

The circuit contains a RESET output which goes low when

the DETECT input drops below 200mV.

*Some Packages Are End Of Life Or Obsolete

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

5V, 3.3V, and 3V output versions

*Optional