NJW4152-AB

- 11 -

Ver.2013-01-23

2. Additional and Protection Functions / Features

Under Voltage Lockout (UVLO)

is low, IC does not operate because the UVLO circuit operates. There is 100mV width hysteresis voltage at rise and

decay of power supply voltage. Hysteresis prevents the malfunction at the time of UVLO operating and releasing.

Soft Start Function (Soft Start)

The output voltage of the converter gradually rises to a set value by the soft start function. The soft start time is

4ms (typ). It is defined with the time of the error amplifier reference voltage becoming from 0V to 0.75V. The soft start

circuit operates after the release UVLO and/or recovery from thermal shutdown. The operating frequency is

controlled with a low frequency, approximately 40% of the set value by the timing resistor, until voltage of the IN- pin

becomes approximately 0.4V.

SW pin

0.8V

FB pin Voltage

ON

OFF

Vref,

IN- pin Voltage

OSC Waveform

Steady

Operaton

UVLO(3.4V typ.) Release,

Standby,

Recover from Thermal

Shutdow n

Soft Start effective period to V

Soft Start time: Tss=4ms(typ.) to V

Low Frequency

Control

V

Fig. 2. Startup Timing Chart

Technical Information

NJW4152-AB Application Manual