TPS51100 Abonormal Vtt!

chunghsienlee

Hi all,

I have a very strange problem with this DDR2 regulator.

We have been used this for production for more than 1 year, sometimes it will fail after assembly.

But this time it's strange as we test modules after assembly and all functions well.

But after we install to mechanical case, memory is not work.

We found the output Vtt of this chip down to 0.3V not 0.9V as expected.

We checked Vin, Vldoin, S3.. all meet specs except Vtt and Vttsns is 0.3V now.

Any idea about what was wrong?

BRs,

Johnson

0 Nancy Zhang over 14 years ago

Hi Johnson,

It is really strange. Did you find the root cause for this failure?

Thanks,

Nancy

0 Nancy Zhang over 14 years ago in reply to Nancy Zhang

Hi Johnson,

Did you find the root cause for the failure?

Thanks,

Nancy

0 chunghsienlee over 14 years ago in reply to Nancy Zhang

Hi Nancy,

Thanks for your tracing on this issue.

After doing some debug work, we noticed some of the DDR by-pass capacitors were short after installation.

This might be the issue why this chip become hot and protection circuitry start working..

We are still monitoring this issue for coming production pcbs.

I will update later once we found anything abnormal.

BR,

Johnson

0 Obed over 14 years ago in reply to chunghsienlee

Johnson,

I am having the same issue with TPS55100DGQ ... Have you noticed more problems after you fixed the DDR by-pass capacitors above mentioned?

Thank you for posting your findings... Will wait for your response.

Obed

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