This document describes a high-frequency synchronous 900 kHz step-down converter based on the ST1S10. It is suitable for powering high-voltage LCD applications and low-voltage digital core HDD applications. The converter provides up to 3 A of output current over an input voltage range of 2.5 V to 18 V. It utilizes synchronous rectification to eliminate the need for an external Schottky diode. The high internal switching frequency of 0.9 MHz allows for the use of small surface-mount components and a resistor divider to set the output voltage. Only an inductor and 3 capacitors are required. The converter operates in current PWM mode and provides stable operation with low output ripple using low E.S.R SMD ceramic capacitors. To maximize power conversion efficiency in light load conditions, the converter can automatically switch to burst mode. It can operate in PWM mode at a fixed frequency or synchronize with an external frequency. The switching frequency is 900 kHz when SYNC is connected to ground or a fixed voltage below 5.5 V, and it can be synchronized between 400 kHz and 1.2 MHz using an external clock applied to SYNC. The converter includes a thermal shutdown circuit that activates at 150 °C and cycle-by-cycle current limitation for protection against shorted outputs.
The document provides an introduction to the ST1S10, a 900 kHz step-down DC-DC converter designed for powering high-voltage LCDs and low-voltage digital cores. It highlights key features such as up to 3 A output current, synchronous rectification eliminating external Schottky diodes, and burst mode operation for light loads.
The device provides up to 3 A over an input voltage range of 2.5 V to 18 V.
The device switches at a fixed frequency of 900 kHz when SYNC is connected to ground or a fixed voltage.
The device enters a dynamic short-circuit protection shutdown mode and turns on again after a specific off time.