July 2000

PRELIMINARY

ML4869

Medium Current Boost Regulator

with Load Disconnect

1

GENERAL DESCRIPTION

The ML4869 is a continuous conduction boost regulator

designed for DC to DC conversion in multiple cell battery

power systems. Continuous conduction allows the

regulator to maximize output current for a given inductor.

The maximum switching frequency can exceed 200kHz,

allowing the use of small, low cost inductors. The ML4869

is capable of start-up with input voltages as low as 1.8V,

and is available in 5V and 3.3V output versions with an

output voltage accuracy of ±3%.

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 current and variable

frequency operation result in high efficiency even at light

loads. The ML4869 requires only a few external

components to build a very small regulator capable of

achieving conversion efficiencies approaching 85%.

The SHDN input allows the user to stop the regulator from

switching, and provides complete isolation of the load

from the battery.

BLOCK DIAGRAM

FEATURES

s

Guaranteed full load start-up and operation at

1.8V input

s

Continuous conduction mode for high output current

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

Low supply current

s

5V and 3.3V output versions

s

Shutdown current = 1µA MAX

VL2

5

VOUT

6

+

–

SHUTDOWN

CONTROL

4

SHDN

VIN

2

2.4V

START-UP

3

GND

VL1

1

SYNCHRONOUS

RECTIFIER

CONTROL

BOOST

CONTROL

SHDN

+

–

+

–

8

PWR GND