LM74502DDFR datasheet(13/29 Pages) TI

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8.3.5 Overvoltage Protection (OV)

LM74502 provides programmable overvoltage protection feature with OV pin. A resistor divider can be

connected from input source to OV pin to ground in order to set overvoltage threshold. An internal comparator

compares the input voltage against fixed reference (1.25 V) and disables the gate drive as soon as OV pin

voltage goes above the OV comparator reference. When the resistor divider is referred from input supply side,

device is configured for overvoltage cut-off functionality. When the resistor divider is referred from output side

(VOUT), the device is configured for overvoltage clamp functionality.

When OV pin voltage goes above OV comparator VOVR threshold (1.25-V typical), the device disables gate

drive, however, charge pump remains active. When OV pin voltage falls below VOVF threshold (1.14-V typical),

the gate is quickly turned on as charge pump is kept on and the device does not go through the device start-up

process. When OV pin is not used, it can be connected to ground.

8.4 Device Functional Modes

8.4.1 Shutdown Mode

The LM74502 enters shutdown mode when the EN/UVLO pin voltage is below the specified input low threshold

V(ENF). Both the gate driver and the charge pump are disabled in shutdown mode. During shutdown mode the

LM74502 enters low IQ operation with the VS pin only sinking 1 µA of current.

8.4.2 Conduction Mode

For the LM74502 to operate in conduction mode the gate driver must be enabled as described in the Gate Driver

(GATE, SRC) section. If these conditions are achieved the GATE pin is

• Internally driven through 60-μA current source in case of LM74502

• Internally connected to the VCAP for fast turn-on of external FET in case of LM74502H

LM74502, LM74502H gate drive is disabled when OV pin voltage is above VOVR threshold or EN/UVLO pin

voltage is lower than VEN/UVLOF threshold.

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LM74502

SNOSDE5 – DECEMBER 2021

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LM74502DDFR Datasheet(PDF) 13 Page - Texas Instruments