AN2903

AN2093 APPLICATION NOTE ST1S03 BUCK CONVERTERS FOR HDD POWER SUPPLIES 1. ABSTRACT The ST1S03 is a step down DC-DC converter optimized for powering the low-voltage digital core in HDD applications and, generally, replacing the high current linear solution when the power dissipation may cause excessive heating of the application environment. It provides up to 1.5A over an input voltage range of 3V to 16V. A high switching frequency (1.5MHz) allows the use of tiny surface-mount components, as well as the use of a resistor divider to set the output voltage value. Only an inductor, a Schottky diode and two capacitors are required. Besides, a low output ripple is guaranteed by the current mode PWM www.DataSheet4U.com topology and by the use of low E.S.R. SMD ceramic capacitors. The device is thermal protected and current limited to prevent damages due to accidental short circuit. The ST1S03 is available in DFN6 (3x3) package. Figure 1: Assembled Board 2. INTRODUCTION Purpose of this application note is to provide a brief summary of the specifications and the functionality of the application board. The ST1S03 is an adjustable current mode PWM step-down DC/DC converter with internal 1.5A power switch. It is a complete 1.5A switching regulator with an internal compensation that eliminates additional components. The constant frequency, current mode, PWM architecture and stable operation with ceramic capacitors results in a low, predictable output ripple. In order to maintain the regul...