LTC4372/LTC4373

10

Rev. 0

For more information www.analog.com

The LTC4372/LTC4373 operate from 2.5V to 80V and

withstands an absolute maximum range of –28V to 100V

without damage. In automotive applications the LTC4372/

LTC4373 can operate through load dump, cold crank and

two-battery jump starts, and survive reverse battery con-

nections while protecting the load.

A 12V/20A ideal diode application is shown in Figure 2.

The following sections cover power-on, ideal diode oper-

ation, shutdown and various faults that the LTC4372/

LTC4373 detect and act upon.

APPLICATIONS INFORMATION

Figure 2. 12V/20A Ideal Diode with Reverse Input Protection

Power-On and Ideal Diode Operation

When power is applied, the initial load current flows

through the body diode of the MOSFET M1. When IN

exceeds the UVLO level of 2.1V and SHDN is low or UV is

high, the LTC4372/LTC4373 begin operation. An internal

charge pump asserts a 20µA pull-up on GATE to enhance

the MOSFET. To achieve a low supply current, the LTC4372/

LTC4373 employ a pulsed control style of operation where

the internal charge pump is not always on. Instead, the

charge pump periodically wakes up to recharge GATE after

control creates a voltage ripple at OUT even with a stable

DC load. The amplitude of this ripple is dependent on gate

leakage, GATE capacitance, the load condition and the size

of the bypass capacitance at OUT. At low load or no-load

for the circuit shown in Figure 2.

With a moderate DC load, the ripple amplitude is about

10mVpk-pk. Figure 4 shows a typical OUT ripple at a mod-

50ms/DIV

43723 F03

IN, OUT

20mV/DIV

IN, GATE

5V/DIV

12V

12V

OUT

GATE

IN

IN

5ms/DIV

43723 F04

IN, OUT

20mV/DIV

IN, GATE

5V/DIV

12V

12V

OUT

GATE

IN

IN

10ms/DIV

43723 F05

IN, OUT

20mV/DIV

IN, GATE

5V/DIV

12V

12V

OUT

GATE

IN

IN

10F

C1

100nF

LTC4372

SHDN

GND

OUT

GATE

= 12V

SOURCE

IN

2UPU

43723 F01

12V

20A

M1

BSC026N08NS5

the circuit shown in Figure 2.