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LTC4359 Recommended for New Designs
The LTC4359 is a positive high voltage ideal diode controller that drives an external N-channel MOSFET to replace a Schottky diode. It controls the forward...
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LTC4359 on Analog.com

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SHDN function doesn't work

NC123

on Oct 5, 2025

Category: Hardware

Product Number: LTC4359

In my design I use SHDN with NMNOS transistor as describe:

When Q4-1 change to on/off the 24V_OUT1 rail is always 24V
SHDN = 0V when Q4-1 is 3.3V
SHDN = 2V when Q4-1 is 0V

hardware and Protection power monitor Ideal Diodes and Load Switches ltc4359 control powerpath Show More

Ashapiro

on Oct 6, 2025 2:06 PM
0
Q2 has probably failed due to exceeding the safe operating area (SOA).
Verify by measuring the resistance from gate to drain to source when the circuit is OFF.
Q2 must be selected to have enough SOA to survive startup.

Also, I recommend not straying too far from fig 6 in the datasheet.
The 1kΩ on VSS is necessary.
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NC123
on Oct 15, 2025 10:21 AM in reply to Ashapiro
0
Why Q2 SOA is not enough to survive startup ?

1K ohm on VSS is not for reverse voltage protection ?
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SHDN function doesn't work