VIPER53-E datasheet(8/36 Pages) STMICROELECTRONICS

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Pin connections and function

VIPer53 - E

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Table 10.

Pin function

Pin Name

Pin function

VDD

Power supply of the control circuits. Also provides the charging current of the external

capacitor during start-up. The functions of this pin are managed by four threshold

voltages:

- VDDon: Voltage value at which the device starts switching (Typically 11.5 V).

- VDDoff: Voltage value at which the device stops switching (Typically 8.4 V).

- VDDreg: Regulation voltage point when working in primary feedback

(Trimmed to 15 V).

- VDDovp: Triggering voltage of the overvoltage protection (Trimmed to 18 V).

SOURCE

Power MOSFET source and circuit ground reference.

DRAIN

Power MOSFET drain. Also used by the internal high voltage current source during the

start-up phase to charge the external VDD capacitor.

COMP

Input of the current mode structure, and output of the internal error amplifier. Allows

the setting of thedynamic characteristic of the converter through an external passive

network. The useful voltage range extends from 0.5V to 4.5V. The Power MOSFET is

always off below 0.5V, and the overload protection is triggered if the voltage exceeds

4.35V. This action is delayed by the timing capacitor connected tothe TOVL pin.

TOVL

Allows the connection of an external capacitor for delaying the overload protection,

which is triggered by a voltage on the COMP pin higher than 4.35V.

OSC

Allows the setting of the switching frequency through an external Rt-Ct network.

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