MPQ4323C 24V to 12V generation issue

DC-DC Power Converters
1

Hello, MPS team,

We are using MPQ4323C to generate 12V from 24V power supply.

Issue description: During bench testing with a regulated DC power supply, the device failed when the input voltage was increased to 30 V DC. After the failure, a short circuit was measured between the pin SW and ground.

Could you please review the attached schematic and advise?

please let me know if you need any further information.

Thank you in advance.

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image1685×481 59.8 KB

2

Hi Shu,

Thank you for posting on the MPS Technical Forum.

A short from SW to GND may be the integrated LS FET failing. The 30V is within the MPQ4323C’s absolute-max rating, so the input voltage itself is not the problem. The most likely root causes are:

  1. SW-node ringing / overshoot: Any parasitic inductance in the SW loop (layout, inductor leads, BOOT path) will produce ringing that can exceed the SW absolute-max and destroy the LS FET.

  2. Inductor saturation: If L100 saturates during a transient, the inductor current flows through the off-state LS FET at 30 V, exceeding its SOA. Please confirm L100’s saturation current rating is comfortably above the HS peak limit (~5.8 A) with margin for the max load.

Could you please share the L100 part number and, if possible, a scope capture of SW during the 24 V → 30 V ramp? That will help us narrow down whether this is a ringing issue or an inductor saturation issue.

Thanks,

Mason