RP515x

No.EA-505-251006

13

Undervoltage Lockout (UVLO) Circuit

When VIN becomes lower than VSET, the buck DC/DC converter stops its switching operation and ON duty

becomes 100%, then VOUT gradually falls according to VIN. When the VIN drops below the UVLO detector

threshold (VUVLOF), the UVLO operates, VREF stops, and PMOS and NMOS built-in switch transistors turn “OFF”.

As a result, VOUT drops according to the COUT1 capacitance value and IOUT. As for RP515xxx1D, the discharge

transistor for COUT1 discharges after it turns on.

To restart the operation, VIN needs to exceed VUVLOR. The timing chart below shows the voltage shifts of VREF,

VLX and VOUT when VIN value is varied.

Note: Falling edge (operating) and rising edge (releasing) waveforms of VOUT could be affected by the initial

voltage of COUT1 and the output current of VOUT.

VOUT

VIN

VUVLOR

VREF

VUVLOF

VLX

VSET

VOUT

Depending on Power Supply,

Load Current, External Components

tSTART

Timing Chart with Variations in Input Voltage (VIN)