UD05208

Preliminary

CMOS IC

UNISONIC TECHNOLOGIES CO., LTD

4 of 5

www.unisonic.com.tw

QW-R115-028.c



DETAILED DESCRIPTION

UD05208 operates with an adaptive on-time control scheme, which is able to dynamically adjust the on-time

duration based on the input voltage and output voltage so that it can achieve relative constant frequency operation.

The device operates at typically 1.5MHz frequency pulse width modulation (PWM) at moderate to heavy load

currents.

Power Save Mode

The device integrates a Power Save Mode with PFM to improve efficiency at light load. When VOUT ≦ 2.5V,

system can enter into Power Save Mode at light load. In Power Save Mode, the device only switches when the

output voltage trips below a set threshold voltage. It ramps up the output voltage with several pulses and stops

switching when the output voltage is higher than the set threshold voltage. PFM is exited and PWM mode entered in

case the output current can no longer be supported in Power Save Mode.

Soft Start

After enabling the device, internal soft-start circuitry monotonically ramps up the output voltage which reaches

nominal output voltage during a soft-start time of 30

0 μs (typical). This avoids excessive inrush current and creates a

smooth output voltage rise slope.

Short Circuit Protection

To avoid mis-operation of the device, short circuit protection is implemented that latch output to GND when output

short.