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ADS7861

Eric Laster
Prodigy 20 points
Other Parts Discussed in Thread: ADS7961, ADS7861

I'm having an issue with the ads7961. I have it configured as a single ended device. However, when I apply a voltage less than the 2.5V reference I get values between 000h and 7FFh. The datasheet indicates these values should be between 800h and FFFh. When I apply a voltage above 2.5V it also returns the CORRECT value between 000h and 7FFh. Can anyone give me any insight as to what I could be doing wrong?

  • 0
    TI__Guru**** 168445 points

    Hi Eric,

    Sounds a little weird...you get 0x000 to 0x7FF for 0-2.5 and then get repeating 0x000 to 0x7FF for 2.5 to 5.0V on the input?  Can you provide a schematic of how you have the ADS7861 connected and perhaps a scope shot of you control lines ( SCLK, SDO, RD, CONVST, etc)?

  • 0 in reply to Tom Hendrick
    Prodigy 20 points

    Hi Tom,

       Thanks for your help. It is weird. As you described it, is exactly as it is happening. Attached is the schematic. Now let me say this, the problem exists only in a single board. We have other pcbs of this exact type and they work as expected. The analog signals all seem fine. I haven't closely probed the digital yet. I haven't tried changing out the chip yet. I wanted to see if anyone has experienced something similar. Thanks for any insight you can provide.