Data Sheet G14309EJ2V0DS00

17

µµµµPC1909

3.5 Overvoltage Protection Operation

The overvoltage latch circuit is a protection circuit that stops the power supply to prevent damage to the load after

detection of overvoltage caused by abnormal boosting of the output of the converter.

The internal configuration of the overvoltage latch circuit is shown in Figure 3-6 below.

Figure 3-6.

µµµµPC1909 Overvoltage Latch Circuit

VTH(OV)

OV

VREF

1

14

SQ

R

To output circuit of OUT1, OUT2

Overvoltage detection comparator

Flip-flop

The threshold voltage (VTH(OV)) connected to the overvoltage detection comparator is 2.0 to 2.8 V (2.4 V TYP.). If the

voltage of the OV pin exceeds VTH(OV), OUT1 and OUT2 are latched to low level. The waveforms when OV (overvoltage)

occurs are shown in Figure 3-7 below.

To reset the status of the overvoltage latch, drop the voltage of the VCC pin to below the OVL release voltage (VR(OV) =

2 V TYP.), and drop the voltage of the VREF pin to a sufficiently low level.

Figure 3-7. Waveforms When Overvoltage Latch Is Operating

OUT1

OV

DTC1

FB

DTC2

OUT2

CT

dCT

T9

td(OV)

VTH(OV)