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Need help on ADS7862 based data acquisition set

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Advanced Member level 4
Dec 12, 2002
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Need help on ADS7862

I'm building data acquisition using ADS7862 and I'm having trouble with it. The output is not corectly represent digital data from the input. What's wrong?

need more clues

We need more clues to solve your problem. Here are some tests to do and report on.

0. Double check the digital number format for what you expect.

1. Are all of the power pins at the right voltage?

2. Is the clock waveform the proper voltage levels and frequency?

3. Put 0V on the analog input and see what the digital output is. Is it what you expect, is it a constant value each conversion time or does it jump around?

4. Put half of full scale DC voltage on the input. Is the digital output what you expect?

5. Apply a very low frequency sine wave on the input and see if the bits toggle. Higher order bits should toggle less frequetly than lower order bits.

If at all possible, put the digital output to a DAC and examine the waveform.

Getting the Full Potential from your ADC

Is REFIN clean? Chip may be working properly but you may have a problem at the digital interface. You should wait until busy is low. Usage of RD and A0 inputs are confusing. It also requires a CMOS compatible clock. Not TTL. You may also check power decopling and routing of power signals.

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