UD052012

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LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

5 of 9

www.unisonic.com.tw

QW-R115-039.a

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FUNCTION DESCRIPTION

The UD052012 is a high efficiency, internal compensation and constant frequency current mode step-down

synchronous DC/DC regulator. It has integrated high-side (140mΩ, typ) and low-side (90mΩ, typ) power switches,

and provides 2A continuous load current. It regulates input voltage from 2.5V to 6V, and down to an output voltage

as low as 0.6V.

Control Loop

Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for

superior load, line response, protection of the internal main switch and synchronous rectifier. The UD052012

switches at a constant frequency (1MHz) and regulates the output voltage. During each cycle, the PWM comparator

modulates the power transferred to the load by changing the inductor peak current based on the feedback error

voltage. During normal operation, the main switch is turned on for a certain time to ramp the inductor current at each

rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage.When

the main switch is off, the synchronous rectifier will be turned on immediately and stay on until next cycle starts.

Enable

The UD052012 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 UD052012 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 UD052012 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).

Short Circuit Protection

The UD052012 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 UD052012 from overheating during the

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

Over Current Protection

The UD052012 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.

Over Temperature Protection

The UD052012 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).

PG Signal Output

PG pin is an open-drain output and requires a pull up resistor. PG is actively held low in soft-start, standby and

shutdown. It is released when the output voltage rises above 90% of nominal regulation point.

Input Over Voltage Protection

The UD052012 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. The hysteretic of the input OVP

comparator is 300mV (typ).