ACE7215A

1.5A 2MHz 6V Synchronous Buck Converter

VER 1.1

7

UVLO and Thermal Shutdown

If VIN drops below 2.1V, the UVLO circuit inhibits switching. Once VIN rises above 2.2V, the UVLO clears,

and the soft-start sequence activates. Thermal-overload protection limits total power dissipation in the

allowing thedieto cool. The thermal sensor turns thedevice on again after the junction temperature cools by

15°C, resulting in a pulsed output during continuous overload conditions. Following a thermal-shutdown

condition, the soft-start sequence begins.

Design Procedure

Input Capacitor Selection

The input capacitor in a DC-to-DC converter reduces current peaks drawn from the battery or other input

power source and reduces switching noise in the controller. The impedance of the input capacitor at the

switching frequency should be less than that of the input source so high-frequency switching currents do not

pass through the input source. The output capacitor keeps output ripple small and ensures control-loop

stability. The output capacitor must also have low impedance at the switching frequency. Ceramic, polymer,

and tantalum capacitors are suitable, with ceramic exhibiting the lowest ESR and high-frequency

impedance. Output ripple with a ceramic output capacitor is approximately as follows:

V

If the capacitor has significant ESR, the output ripple component due to capacitor ESR is as follows:

V