Charge Pump

Enable Logic

+

±

Q

R

S

Q

+

±

+

±

+

±

GM AMP

+

±

+

±

20 mV

50 mV

-5 mV

COMPARTOR

COMPARTOR

ENABLE LOGIC

GATE DRIVER

ENABLE

LOGIC

REVERSE

PROTECTION

LOGIC

Bias Rails

ANODE

GATE

CATHODE

VCAP

EN

GND

Charge

Pump

Copyright © 2017, Texas Instruments Incorporated

6

LM74700-Q1

SNOSD17 – OCTOBER 2017

www.ti.com

Product Folder Links: LM74700-Q1

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Copyright © 2017, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The LM74700-Q1 ideal diode control 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

charge pump allows the N-channel MOSFET to be enhance without refresh pulses that disable the N-channel

MOSFET. 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 drive the N-channel MOSFET. During light load

currents, the forward voltage drop of the N-channel MOSFET is regulated to 20 mV. At heavier load conditions,

selected MOSFET. A reverse current condition is detected when there is –5 mV between the ANODE and

CATHODE pin, resulting in the GATE pin being internally connected to the ANODE pin turning off the external N-

channel MOSFET, and utilizing the body diode to block any the reverse current. An enable pin (EN) is available

to place the LM74700-Q1 in shutdown mode disabling the N-Channel MOSFET and minimizing the quiescent

current.

7.2 Functional Block Diagram