LTC4373CMS8 datasheet(10/20 Pages) AD

10 / 20 page

LTC4372/LTC4373

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

it droops from leakage to keep ∆VSD ≤ 30mV. This pulsed

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

condition, this ripple can increase to 30mVPK–PK. Figure 3

shows a typical OUT ripple at an ultralight ILOAD of 1µA

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-

erate ILOAD of 2A for the circuit shown in Figure 2.

Figure 3. Regulating ∆VSD at

Low ILOAD = 1µA

Figure 4. Regulating ∆VSD at

Moderate ILOAD = 2A

Figure 5. Regulating ∆VGATE at

High ILOAD = 16A

50ms/DIV

43723 F03

IN, OUT

20mV/DIV

IN, GATE

5V/DIV

12V

IGATE(LEAKAGE) = 100nA

OUT

GATE

5ms/DIV

43723 F04

IN, OUT

20mV/DIV

IN, GATE

5V/DIV

12V

IGATE(LEAKAGE) = 100nA

OUT

GATE

10ms/DIV

43723 F05

IN, OUT

20mV/DIV

IN, GATE

5V/DIV

12V

IGATE(LEAKAGE) = 100nA

OUT

GATE

COUT

10F

100nF

LTC4372

SHDN

GND

OUT

GATE

= 12V

SOURCE

2UPU

INTVCC

43723 F01

VOUT

12V

20A

VIN

BSC026N08NS5

Figure 5 shows a typical OUT ripple at an ILOAD of 16A for

the circuit shown in Figure 2.

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