Data brief

For further information contact your local STMicroelectronics sales office.

September 2009

Doc ID 14449 Rev 2

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STEVAL-ISA044V2

3 A synchronous 900 kHz step-down DC-DC converter

with inhibit function based on the ST1S10

Features

synchronized to an external frequency

between 400 kHz and 1.2 MHz

µA in inhibit state

Description

The ST1S10 is a step-down DC-DC converter

with inhibit function optimized for powering high

voltages in LCD applications and low voltage,

digital core HDD applications. It replaces the high

current linear solution when high power

dissipation is a problem. It provides up to 3 A over

an input voltage range of 2.5 V to 18 V, and

synchronous rectification removes the need for an

external Schottky diode. A high internal switching

frequency (900 kHz) allows for the use of tiny

surface-mount components, as well as the

resistor divider to set the output voltage value.

Only an inductor and 3 capacitors are required.

The current mode PWM architecture and stable

operation with low-ESR SMD ceramic capacitors

result in low output ripple. To maximize power

conversion efficiency in light load, the regulator

can work in burst mode automatically. The device

can operate in PWM mode with a fixed frequency

or synchronized to an external frequency. It

switches at a frequency of 900 kHz when the

SYNC pin is connected to ground or a fixed

voltage (less than 5.5 V), and can synchronize the

switching frequency between 400 kHz to 1.2 MHz

from external clock that is applied to SYNC pin. A

thermal shutdown circuit is integrated and

activates at 150 °C. Cycle-by-cycle current

limitation provides protection against shorted

outputs.

The quiescent current is less than 6

µA in inhibit

state. The device is available in MLP4x4 and

SO-8 ePad packages.

STEVAL-ISA044V2

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