strange Signal at ADC input


strange Signal at ADC input

490 次查看
Contributor II

Hello all,

I see a strange signal at ADC input which might cause the issue I am faced with.

I have attached the osci picture.

This signal looks like a sawtooth wave.

When I change the paramter SMPLTS then the area marked on the picture changes accordingly.

So I assume that when the ADC does "sample" the signal is forced to input level.

When the ADC does "hold" for internal sampling the signal follows a sawtooth wave.

I do not see this signal analysing the sample values. However the sampled signal does not match what I expect. Also I have

issue processing it.

The ADC input in connected with 1nF capacitor to ground.

Does anybody has n idea why this signal is so strange? What do I need to do here?

Thanks for your help

2 回复数

404 次查看
Contributor II

Hello Daniel,
I found an Application Note 

It seems that is the root cause ie the input impadance does not match.
I will check that

BR Edgar

404 次查看
NXP TechSupport
NXP TechSupport

Could you please send the schematic and describe the ADC operation in more details?

BR, Daniel

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