DRV8801 VCP current?

Michel Noxfeld

Other Parts Discussed in Thread: DRV8801

I'm using the DRV8801 to drive a DC motor at 10V, max current 1.5 A, no PWM.
The motor is driving a gearbox with some load on it and we are testing the concept by driving the motor in a continuous cycle:
Start Clockwise --> Delay --> Stop/Break using slow decay mode. Then same cycle again but counter clockwise. Delay is 3 sec.
After some 200 000 cycles VCP capacitor just blew up in pieces.

Now I'm trying to find in the data sheets what minimum current rating I should have on the VCP capacitor - but I can't find any figures.

A hint would be very much appreciated.

Cheers,

Michel

over 12 years ago

0 Milan Rajne over 12 years ago

TI__Expert 8885 points

Michel,

What is voltage rating of VCP capacitor in your application? Due to repetative braking in your application, there are chances that DC bus voltage transiently shoot-up higher than VCP capacitor voltage rating. This phenomenon can slowly reduce the MTBF of VCP capacitor.

Please increase the voltage rating of Capacitor and re-test, meanwhile I will check the current rating figure for VCP capacitor from factory and let you know soon, if they have some info on this.

Best Regards

Milan Rajne

System Application-Motor Control

0 Michel Noxfeld over 12 years ago in reply to Milan Rajne

Prodigy 30 points

I'm using the specified 0.1 uF / 50V cap. Thought it should be enough for a 10V input.

I'll try 100V in next test set-up.

Regards,

Michel

0 Ryan Kehr over 12 years ago in reply to Michel Noxfeld

TI__Guru 55615 points

Michel,

50V should be more than enough! It is possible you had a defective cap. I have never seen this before. How many boards did you experience this failure on?

What was the temperature of the cap during your testing?

This is the capacitor we used on the EVM. I have blown up a lot of things, but never a ceramic capacitor. Might need to check with the cap manufacturer.

http://www.digikey.com/product-detail/en/C0805C104K3RACTU/399-1168-2-ND/411167

0 Michel Noxfeld over 12 years ago in reply to Ryan Kehr

Prodigy 30 points

This is the first board we're testing.

We're using this cap: http://www.digikey.com/product-detail/en/C1608Y5V1H104Z/445-1324-6-ND/615270

It's an Y5V (0603), not X7R and I realize this cap is pretty much useless for this application.

Regards,

Michel

0 Ryan Kehr over 12 years ago in reply to Michel Noxfeld

TI__Guru 55615 points

Michel,

Prefer X7R as you pointed out already, but the other thing to note is the 85C temperature rating. Are you within this bound during your testing?

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DRV8801 VCP current?