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ADM1172 issue

Question asked by brent.chang@wpi-group.com on Jul 29, 2015

Hi,

 

Is ADM1172 suitable for using as an efuse for system Fan?

Recently we find out that the ADM1172 will turn off the gate and it caus the system fan unpowered. This issue happens sometimes and .

The weird part is the output current is only half of the OCP threshold.

 

As below waveform shows, the max fan current is only 5.76A. (Designed OCP is 14.52A)

hotswap_failed7.png

 

I also check the Vtimer (Purple), its ramping time is weird also .

hotswap_100_curremt drop2.png

The Ctimer is 0.022uF. Ton is 0.476ms, which means  MOSFET should turn off in 0.476ms when overcurrent is triggerred. But the waveform shows the ramp up time is more than 0.476ms.

 

This is the design schematic,for reference

未命名.jpg

Could you please help check this issue and how to solve it, thanks!

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