strange ADC spikes

Mar 05, 2005 2 Replies
O

Hello,



I'm experiencing voltage spikes on the output, but the strange thing about that is these spikes are generated only if the input voltage reaches certain levels and it doesn't matter how I "clock" the ADC (2KHz to 40MHz). (ADC is 8bit TDA8703) For example when the input constant signal is in the middle D7:D0=128 there are spikes to D7:D0=255, another example input signal should be convert to something about D7:D0=150 but there are spikes to the level of 170. There are several more levels where these spikes are generated. At differentinput voltage levels spikes have different amplitude, but constant for a certain levels. I assume this is not a standard noise.



What's wrong with it ? :(



thanks in advance



Olo



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J

It may be normal. Are you sampling the data at the proper "valid" time relative to the clock? It has a right to do anything outside the valid-data window.

But it's a discontinued part!

John

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O

No, I've been taking samples at any time, but when I'm looking at timing diagram I've been doing wrong :). I'll check this out.

yes, but quite cheap and easy to get in Poland

thanks for advice

olo

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