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How to Choose the Channel of ADS7865

Other Parts Discussed in Thread: ADS7865

From the datasheet of ADS7865, I found that ADS7865 can be used as 3+3 channel or 2+2 channel. But I want to use3+2 channel in my application. So I have some questions about ADS7865 that is how to choose Channel A or Channel B when I configure it . Can ADS7865 be used as 3+2 channel?

Thanks for your answer.

  • Hi,

    This device is supported by the precision data converter team. I will move the thread to the appropriate forum.

    Regards,
    Matt Guibord
  • ok,thank you! I'm new here, so thanks for your help!
  • Hi there user4252417,

    The ADS7865 does not let you choose CHA or CHB, its always going to give you both A and B because of the simultaneous sampling nature of this converter. The multiplexer configuration is described in tables 1 and 2 on page 14 of the datasheet. The two MSB's of the configuration register control how the mux selection is made (see tables 4 and 5 on page 17). To get a 3+2 configuration, for example where CHA is set as three pseudo-differential inputs and CHB is set as two fully differential inputs, you would have to cycle through all four possible combinations of bits C1 and C0.

    Your CHA pseudo-differential data will be valid with C1, C0 combinations of '00', '01' and '10'. The CHB fully differential data will be valid with C1, C0 combinations '00'and '11'. Since two reads are required to get both CHA and CHB conversion results (see figure 32), you can either ignore the CHB data when C1/C0 = '01' or '10' or just do a single read to get only CHA conversion results. You would also want to ignore the CHA conversion results when C1/C0 = '11'.

  • ok, I konw. Thanks for your help!