UD05124

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LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

5 of 9

www.unisonic.com.tw

QW-R115-038.c

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FUNCTION DESCRIPTION

The UD05124 is a high efficiency, internal compensation and constant frequency current mode step-down

synchronous DC/DC converter. It has integrated high-side (340mΩ, typ.) and low-side (210mΩ, typ.) power switches,

and provides 1.2A continuous load current. It regulates input voltage from 2.5V to 6V, and down to an output voltage

as low as 0.6V.

Enable

The UD05124 EN pin provides digital control to turn on/off the regulator. When the voltage of EN exceeds the

threshold voltage, the regulator will start the soft start function. If the EN pin voltage is below the shutdown threshold

voltage, the regulator will turn into the shutdown mode and the shutdown current will be smaller than 1μA. For auto

start-up operation, connect EN to VIN.

Soft Start

The UD05124 employs internal soft start function to reduce input inrush current during start up. The internal soft

start time will be 1ms.

Under Voltage Lockout

When the UD05124 is power on, the internal circuits will be held inactive until VIN voltage exceeds the UVLO

threshold voltage. And the regulator will be disabled when VIN is below the UVLO threshold voltage. The hysteretic of

the UVLO comparator is 200mV (typ).

Input Over Voltage Protection

The UD05124 supports input over voltage protection. When input voltage exceeds the input over voltage threshold,

the regulator will be shutdown unless the input over voltage is removed.

Over Current Protection

The UD05124 over current protection function is implemented by using cycle-by-cycle current limit architecture.

The inductor current is monitored by measuring the high-side MOSFET series sense resistor voltage. When the load

current increases, the inductor current will also increase. When the peak inductor current reaches the current limit

threshold, the output voltage will start to drop. When the over current condition is removed, the output voltage will

return to the regulated value.

Short Circuit Protection

The UD05124 provides short circuit protection function to prevent the device damaged from short condition. When

the short condition occurs and the feedback voltage drops lower than 40% of the regulation level, the oscillator

frequency will be reduced and hiccup mode will be triggered to prevent the UD05124 from overheating during the

extended short condition. Once the short condition is removed, the frequency and current limit will return to normal.

Over Temperature Protection

The UD05124 incorporates an over temperature protection circuit to protect itself from overheating. When the

junction temperature exceeds the thermal shutdown threshold temperature, the regulator will be shutdown. And the

hysteretic of the over temperature protection is 30°C (typ).