DRV8840: abnormal heat of chip occurs

Cherry Zhou

Part Number: DRV8840

Hi team,

Here's an issue from the customer may need your help:

The device outputs and connects 104 capacitors on OUT1, OUT2, drives at 25 KHz, 80% duty cycle, circuit around 1A. Why the chip would have abnormal heat condition? The chip does not heat up at 100% duty cycle.

Could you help check this case? Thanks.

Best Regards,

Cherry

over 2 years ago

0 Ryan Kehr over 2 years ago

TI__Guru 55015 points

Cherry,

What is the supply voltage? I assume that 104 = 0.1uF value.

If they remove those caps, I assume the heat issue is gone?

I = C * DV/DT - that will be the inrush current on every rising edge of the output square wave. That will cause excessive heat.

Regards,

Ryan

0 Cherry Zhou over 2 years ago in reply to Ryan Kehr

TI__Mastermind 22235 points

Hi Ryan,

Thanks for your help.

VM 24V.

Ryan Kehr said:
If they remove those caps, I assume the heat issue is gone?

Yes, after removing the caps, heat issue is gone.

Ryan Kehr said:
I = C * DV/DT

Is DT referring to tR and tF?

Thanks and regards,

Cherry

0 Ryan Kehr over 2 years ago in reply to Cherry Zhou

TI__Guru 55015 points

Cherry,

Yes, DT is "delta time", so Trise is the important spec here as the capacitor on the output is charged on this rising edge.

Regards,

Ryan

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DRV8840: abnormal heat of chip occurs