Data Sheet G14309EJ2V0DS00

26

µµµµPC1909

4.6 Remote Control

In the

µPC1909, starting up and stopping a converter can be controlled by turning on and off the output circuit using an

external signal. When the ON/OFF pin is made low level, the low voltage malfunction protection circuit operates and

cuts off OUT1 and OUT2, causing the timing capacitor connected between the CT pin and GND (CT) and the soft start

capacitor connected between the DTC1 pin and GND to discharge. Because the on/off threshold voltage has 0.2-V

hysteresis, the occurrence of chattering can be suppressed, even in slow on/off operations.

The ON/OFF pin is internally pulled up to VREF via a 100 k

Ω resistor. When the on/off function is not used, however, be

sure to connect the ON/OFF pin directly to the VREF pin in order to prevent the occurrence of noise.

A configuration whereby on/off control is controlled from the primary side by a photocoupler is shown in Figure 4-10

below. Be sure to set the pull-down resistor connected to the ON/OFF pin so that the leakage current between C and E

when the photocoupler is off does not cause the ON/OFF pin voltage to be boosted to a level whereby the

µPC1909 is

turned on.

Figure 4-10. ON/OFF Pin Connection

VREF

ON/OFF

GND

3

7

14

2.6 V/2.4 V

100 k

Ω

Photo-

coupler