UCD9090A: MONx noise

Mark Pieper

Part Number: UCD9090A
Other Parts Discussed in Thread: OPA2333,

My customer is driving the MON1 pin with an op-amp at 0.56V. It is an OPA2333 micropower op amp. They are seeing a noise transient on the op-amp output (MON1 pin) at around 100mV with a frequency of ~130KHz. They are using MON1-7, MON8-11 are unused. There is no external capacitance on the MON1 pin to GND. Feedback resistance around the op-amp is 10K ohms.

Is it possible that the internal UCD9090A MUX is introducing this noise on the MON1 pin? Any other thoughts about what might be causing this- it does not correlate to anything in or around the op-amp. Everything is very clean.

Thanks, Mark

over 6 years ago

0 Mark Pieper over 6 years ago

TI__Expert 4430 points

Update: The frequency isn't 130KHz, but is closer to 35KHz. See the scope pic below.

Could this be crosstalk in the mux?

0 Brian Gosselin over 6 years ago in reply to Mark Pieper

TI__Expert 4575 points

To add to Mark's question, I believe the ringing frequency is about 400kHz (1/(2.5*10^(-6))) with a burst every 35us (~28kHz).

I'm interested in your feedback regarding whether or not this could be due to crosstalk in the MUX.

0 yihe over 6 years ago

TI__Guru 57940 points

Hi Mark

Do you have customer's schematics? Is the same noise observed on the mon2-7 pins?

Regards

Yihe

Power management

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UCD9090A: MONx noise