MCT8316A: Damage Issue During Power ON/OFF Operations

Tool/software:

Hi,

I am currently experiencing trouble with the MCT8316A, and would like to confirm the following situation.

【Overview】

• IC in use: MCT8316A
• Power Supply: 12V DC (with 4A current limit)
• Board spec: Double-sided PCB
• Load: Small fan (light load)
• Condition of occurrence: Occurs when power ON/OFF is repeated
• Timing of occurrence: Immediately after power ON
• IC status after failure: Short circuit between VM and GND, IC emits smoke, completely non-functional

【Confirmed Phenomenon】

• When powering on, sometimes the motor runs, and sometimes it does not, showing unstable behavior.
• After several ON/OFF operations, the IC gets damaged, causing a short circuit on the power line.
• According to observed power supply ramp-up waveforms, a rapid voltage rise seems to correlate with IC failure.
• We have collected and compared waveforms for cases with and without IC damage:
  • White trace: Sequence when failure occurred
  • Blue trace: Sequence when failure did not occur
    
    

【Consideration】
① We are concerned that regenerative current may be flowing back to the VM line during repeated ON/OFF cycles. If there is no proper path to absorb this energy, it may cause the VM voltage to exceed the IC's absolute maximum rating, leading to failure.
② There is a possibility that power ramp-up and ramp-down characteristics influence whether the IC gets damaged.

【Our Questions】

1. Could you share your thoughts on consideration ①, regarding the potential risk of IC absolute maximum rating being exceeded due to regenerative current flowing into VM?
2. Could you advise on possible causes and factors based on the fact that IC failure is dependent on the power ramp-up/down waveforms?
3. Although we are using a 12V DC power supply with a 4A limit, what kind of behavior and risks would be expected if we operate the system using a battery without current limitation?

Thanks,

Conor