WRN78XXT-500

WRN78XXT-500

WRN78XXT-500

WRN78XXT-500

WRN78XXT-500

WRN78XXT-500

WRN78XXT-500

Series

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Technical Enquiries-Email:tech@microdc.cn Tel:0086-20-86000646

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SHUTDOWN

SHUTDOWN

SHUTDOWN

SHUTDOWN

SHUTDOWN

SHUTDOWN

SHUTDOWN

CONTROL

CONTROL

CONTROL

CONTROL

CONTROL

CONTROL

CONTROL

The ON/OFF pin provides several features for adjusting and sequencing the power supply, a user has the flexibility of using the ON/OFF pin as:

1) A digital on/off control by pulling down the ON/OFF pin with an open-drain transistor.

2)

Line UVLO. If desired to achieve a UVLO voltage, an resistor divider from Vin to ON/OFF to GND can be used to disable the converter until

a higher input voltage is achieved. For example , it is not useful for a converter with 12V output to start up with a 12V input voltage, as the output

cannot teach regulation. To enable

the converter when

the input voltage reaches 14V , a 51kΩ ⁄ 5kΩ resistor divider from Vin to GND can be

connected to the ON

⁄

OFF pin . Both the precision 1.25V threshold and 150mV hysteresis are multiplied by

the resistor ratio , providing a

proportional 12% hysteresis for any startup threshold. So , the turn off threshold would be between 12.3V to 15.7V.

3)

Power supply sequencing. By connecting a small capacitor from ON/OFF to GND, the 2µA current source and 1.25V threshold can provide a

stable and predictable delay between startup of multiple power supplies. For example, a startup delay of roughly 64mS is provided using 100nF, and

roughly 136mS by using 200nF.