• The VCAP to ANODE voltage must be greater than the undervoltage lockout voltage.

• The ANODE voltage must be greater than VANODE POR Rising threshold.

If the above conditions are not achieved, then the GATE pin is internally connected to the ANODE pin, assuring

that the external MOSFET is disabled. Once these conditions are achieved, the gate driver operates in the

correct mode depending on the ANODE to CATHODE voltage.

8.3.4 Enable

The LM74700-EP has an enable pin, EN. The enable pin allows for the gate driver to be either enabled or

disabled by an external signal. If the EN pin voltage is greater than the rising threshold, the gate driver and

charge pump operates as described in Gate Driver and Charge Pump sections. If the enable pin voltage is less

than the input low threshold, the charge pump and gate driver are disabled placing the LM74700-EP in shutdown

mode. The EN pin can withstand a voltage as large as 65 V and as low as –65 V. This ability allows for the

EN pin to connect directly to the ANODE pin if enable functionality is not needed. In conditions where EN is left

floating, the internal sink current of 3 uA pulls EN pin low and disables the device.

8.4 Device Functional Modes

8.4.1 Shutdown Mode

The LM74700-EP enters shutdown mode when the EN pin voltage is below the specified input low threshold

shutdown mode, forward current flow through the external MOSFET is not interrupted but is conducted through

the MOSFET's body diode.

8.4.2 Conduction Mode

Conduction mode occurs when the gate driver is enabled. There are three regions of operating during

conduction mode based on the ANODE to CATHODE voltage of the LM74700-EP. Each of the three modes

is described in the Regulated Condution Mode, Full Conduction Mode and Reverse Current Protection Mode

sections.

8.4.2.1 Regulated Conduction Mode

For the LM74700-EP to operate in regulated conduction mode, the gate driver must be enabled as described in

the Gate Driver section, and the current from source to drain of the external MOSFET must be within the range

to result in an ANODE to CATHODE voltage drop of –11 mV to 50 mV. During forward regulation mode, the

ANODE to CATHODE voltage is regulated to 20 mV by adjusting the GATE to ANODE voltage. This closed loop

regulation scheme enables graceful turn off of the MOSFET at very light loads and ensures zero DC reverse

current flow.

8.4.2.2 Full Conduction Mode

For the LM74700-EP to operate in full conduction mode, the gate driver must be enabled as described in the

Gate Driver section. The current from source to drain of the external MOSFET must be large enough to result

in an ANODE to CATHODE voltage drop of greater than 50-mV typical. If these conditions are achieved, the

GATE pin is internally connected to the VCAP pin resulting in the GATE to ANODE voltage being approximately

minimized, reducing the power loss of the external MOSFET when forward currents are large.

8.4.2.3 Reverse Current Protection Mode

For the LM74700-EP to operate in reverse current protection mode, the gate driver must be enabled as

described in the Gate Driver section, and the current of the external MOSFET must be flowing from the drain

to the source. When the ANODE to CATHODE voltage is typically less than –11 mV, reverse current protection

mode is entered and the GATE pin is internally connected to the ANODE pin. The connection of the GATE to

ANODE pin disables the external MOSFET. The body diode of the MOSFET blocks any reverse current from

flowing from the drain to source.

LM74700-EP

SNOSDD6 – SEPTEMBER 2021

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