UCD9246: DPWM-1a runaway

Allan Green

Part Number: UCD9246
Other Parts Discussed in Thread: UCD7242,

On our last build of PCAs, the UCD9246 power controller is losing control of the DPWM-1a output. Either at powerup, or with a slight freeze spray the DPWM-1a goes from 12.5% duty cycle (1.5V output from 12V) to 50%. This causes the UCD7242 driver to boost the 1.5V output, current goes from 0.5A to 10A+, and the UCD7242 FLT asserts. The UCD9246 DPWM-1a stops and the whole controller shuts of per it's fault programming. This part has been in stready use for 12 years and this seems lot related. Can you contact me and help with this issue?

over 2 years ago

0 Nastasha over 2 years ago

TI__Genius 10000 points

Hi Allan,

Can you clarify if this behavior occurred with 1 unit or multiple units? If only with 1 unit, did you try that unit on a different board?

Thanks,

Nastasha

0 Allan Green over 2 years ago in reply to Nastasha

Prodigy 10 points

Hi Natasha - this is occuring on about 30 boards. We have probed about 10 of them and the mechanism looks the same, DPWM-1a goes to 50% and the UCD7242 FLT-1a occurs. We have scope traces.

0 Allan Green over 2 years ago in reply to Allan Green

Prodigy 10 points

I have datecodes also

0 Nastasha over 2 years ago in reply to Allan Green

TI__Genius 10000 points

Allan,

A few thoughts on this:

1. If you can verify the units were purchased directly from TI, you can submit a return request here: https://www.ti.com/productreturns/docs/createReturn.tsp

2. Can you also show some scopeshots of what is going on with the the PWM signal, the output voltage, and the load during this scenario?

3. Have you tried one of these units on a different board? Does the behavior follow the unit?

Thanks,

Nastasha

0 Allan Green over 2 years ago

Prodigy 10 points

Hi Natasha -

Sorry lots of channels opened for support. Here is a scope picture of a typical failure, which happens on several boards. This seems to be the common failure, I have seen it in my lab on several boards, and so has Yigal in his lab in Israel.

How do I insert or send a scope shot jpeg? Insert/image,video,file asks for a URL. How do I get you my jpg file?

0 Murali Malla over 2 years ago in reply to Allan Green

TI__Intellectual 795 points

Hi Allan,

Have you got a chance to test the units which are showing the issue on a known working board?

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UCD9246: DPWM-1a runaway