Data brief

For further information contact your local STMicroelectronics sales office.

October 2011

Doc ID 022401 Rev 1

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STEVAL-ISA044V6

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

with inhibit function based on the ST1S10 (DFN)

Features

synchronized to an external frequency

between 400 kHz and 1.2 MHz

Description

The STEVAL-ISA044V6 demonstration board is

based on the ST1S10 device assembled in a DFN

package. The ST1S10 is a step-down DC-DC

converter with the inhibit function optimized for

powering high voltages in LCD applications and

low voltages in digital-core HDD applications. It

replaces the high-current linear solution when

high power dissipation is an issue.

It provides up to 3 A over an input voltage range

of 2.5 V to 18.0 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 a 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 an external clock applied to the 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

the inhibit state.

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