1/11

October 2002

s

CONVERTS +4.0V TO + 6.2V INPUT TO -5V

OUTPUT (735S) OR +3.5V TO + 9.0V TO A

NEGATIVE ADJUSTABLE OUTPUT (735T)

s

1W GUARANTEED OUTPUT POWER

s

72% TYPICAL EFFICIENCY

s

0.8mA QUIESCENT CURRENT

s

1µA SHUTDOWN MODE

s

300KHZ FIXED FREQUENCY OSCILLATOR

s

CURRENT MODE PWM CONVERTER

s

LOW NOISE AND JITTER

s

SOFT START

s

SIMPLE APPLICATION CIRCUIT

s

UNDERVOLTAGE LOCKOUT (735S)

DESCRIPTION

The ST735S/ST735T is a Bi-CMOS, inverting

switch mode DC-DC regulator with internal Power

MOSFET that generates a fixed -5V (S version) or

a negative adjustable (T version) output voltage

from a 4V (3.5V for the 735T) to 6.2V input voltage

(9V for the 735T); is guaranteed an output current

of 200mA for inputs greater than 4.5V. The

quiescent current for this device is typically of

0.8mA and, in shutdown mode it is reduced to

1µA.

These power-conserving features, along with high

efficiency and applications circuits, thaT lend itself

to minaturization, make the ST735S/ST735T

excellent in a broad range of on-card, HDD and

portable equipment

applications. These device

employ a high performance current mode pulse

with modulation (PWM) control scheme to provide

tight output voltage regulation and low noise. The

fixed frequency oscillator is factory trimmed to

300KHz, allowing for easy noise filtering. The

regulator in production is tested to guarantee an

output accuracy within ±5% over all specified

conditions.

ST735S

ST735T

300kHz, -5V/ADJ INVERTING, NEGATIVE OUTPUT

CURRENT-MODE PWM REGULATOR

SCHEMATIC DIAGRAM

DIP-8

SO-8