WRN78XXT-500 Datasheet, PDF (4/6 Pages) Microdc power Technology Co., Ltd – WIDEINPUT,NON-ISOLATED®ULATED SMDPACKAGE SINGLEOUTPUT

WRN78XXT-500 Series
SHUTDOWN 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.
http://www.microdc.cn Technical Enquiries-Email:[e-mail] Tel:[phone] Page 4 of 6