MPQ5872 Hot Plugging Issue in Prototype

[mikey.parry]

Hello,

I’ve integrated the MPQ5872GRPE-AEC1-Z into my design to provide inrush current protection and soft-start functionality. Initial development and testing with the evaluation board showed promising results, so I proceeded with building a prototype.

However, during testing of the prototype, I’ve encountered an issue I can’t quite pinpoint. When the MPQ5872 is powered via a bench supply and I toggle power using the supply’s on/off switch, the system works as expected. But when I hot-plug the supply (i.e., connect the power while the supply is already on), the MPQ5872 appears to enter a hiccup mode and fails to recover.

I suspect this might be related to inrush current, though my understanding was that this device is specifically designed to manage such conditions.

Additional observations:

• If I bypass the MPQ5872 by directly connecting VIN and VOUT, the rest of the system operates normally, which leads me to believe the issue is isolated to the MPQ5872.
• VIN is stable at 12V.
• EN is held at 2.48V via a voltage divider.
• ILIM uses a 348Ω resistor. The system is designed to draw a maximum of 2A.
• SS has a 22nF capacitor. I’ve also tried increasing it to 100nF and 200nF, but this had no effect.

Upon hot-plugging, VOUT ramps to 12V over ~44ms, then collapses and retries after ~430ms, suggesting the device is in some form of restart or fault cycle.

Any insights or suggestions would be greatly appreciated.

Output Trace

[roman.vallsguimera]

I’d check how hot it gets with a thermal camera? Sounds like some kind of thermal shutdown?

[mikey.parry]

Hi,
I believe ive found the issue. I didnt realise that another IC had a an internal 30ms delay. So the MPQ5872 would perform a softstart and then the other device would wait 30ms before enabling the load therefor dumping a load of current causging the MPQ5872 to overcurrent.

Thanks,
Mike