8 Detailed Description

8.1 Overview

The LM74700-EP ideal diode controller has all the features necessary to implement an efficient and fast

reverse polarity protection circuit or be used in an ORing configuration while minimizing the number of external

components. This easy to use ideal diode controller is paired with an external N-channel MOSFET to replace

other reverse polarity schemes, such as a P-channel MOSFET or a Schottky diode. An internal charge pump

is used to drive the external N-Channel MOSFET to a maximum gate drive voltage of approximately 15 V. The

voltage drop across the MOSFET is continuously monitored between the ANODE and CATHODE pins, and the

GATE to ANODE voltage is adjusted as needed to regulate the forward voltage drop at 20 mV. This closed

loop regulation scheme enables graceful turn off of the MOSFET during a reverse current event and ensures

zero DC reverse current flow. A fast reverse current condition is detected when the voltage across ANODE and

CATHODE pins reduces below –11 mV, resulting in the GATE pin being internally connected to the ANODE pin

turning off the external N-channel MOSFET, and using the body diode to block any of the reverse current. An

enable pin, EN, is available to place the LM74700-EP in shutdown mode, disabling the N-Channel MOSFET and

minimizing the quiescent current.

8.2 Functional Block Diagram

Charge Pump

Enable Logic

+

±

Q

R

S

Q

+

±

+

±

+

±

GM AMP

+

±

+

±

20 mV

50 mV

-11 mV

COMPARATOR

COMPARATOR

ENABLE LOGIC

GATE DRIVER

ENABLE

LOGIC

REVERSE

PROTECTION

LOGIC

Bias Rails

ANODE

GATE

CATHODE

VCAP

EN

GND

Charge

Pump

Copyright © 2017, Texas Instruments Incorporated

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LM74700-EP

SNOSDD6 – SEPTEMBER 2021

Copyright © 2021 Texas Instruments Incorporated

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Product Folder Links: LM74700-EP