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ADS8860 has wrong readings

Radoslaw
Prodigy 70 points

Other Parts Discussed in Thread: ADCPRO

Hello,

I was testing the ADS8860EVM - i set the software up, checked the jumpers and pluged it all in, and then there's the catch: 

to see quickly if the conversion is there, i combined the AO pin with GND, just to see the bunch of zeros, the problem is, what i saw on the ADCPro Multiscope was ~2.245V. I checked it with abother EVM board i have (different MMB0 + ADS8860EVM) and  the same value popped up. I have checked if the ADC gets the correct voltages - it does (4.5 Vref, +5 VDD). It runs in bipolar mode now. What did I miss?

  • 0
    TI__Expert 6925 points

    Hello Radoslaw,

    The reading is correct. If JP4 is installed and A0 pin is grounded, the voltage at the ADC input should be ≈Vref/2 or 2.25V according to the transfer function AINP = 2.25V – A0:

    The confusion is that EVM User-Guide titles in sections 3.1 and 3.2 are backwards:
    Section 3.1 title should be “Bipolar Input Signal Configuration”
    Section 3.2 title should be “Unipolar Input Signal Configuration”
    We will fix this within the next couple of weeks.

    Thank you,
    Rafael

  • 0 in reply to Rafael Ordonez
    Prodigy 70 points

    Hello Rafael

    Thank You for the explanation. Shame on me for missing that one.

    Kind regards!
    radek