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ADS8166: Does Auto Sequence Mode work with Pairing on the ADS8166

Thomas Blocher
Intellectual 475 points
Part Number: ADS8166

Tool/software:

Hi,

I have two pairs of input pins (AIN0 & AIN1, and AIN2 & AIN3), and I would like to use auto-sequence mode. 

If I configure the inputs as separate channels (e.g.CH1_CH0_CFG[1:0] = 0), then the measurement is correct. 
If I configure the inputs as pairs, it does not work.

Does Auto Sequence Mode work with Pairing?

If yes, how do I configure the registers AIN_CFG and AUTO_SEQ_CFG1?

  • 0
    TI__Expert 8545 points

    Hi Thomas,

    Thanks for your post. What does the measurement look like when you are using auto sequencing with input pairs? Are you using the pairs as single-ended inputs or pseudo differential channels?

    Best regards,

    Samiha

  • 0 in reply to Samiha Sharif
    Intellectual 475 points

    Hi Samiha!

    The measurement looks just strange; I did not find any logic in the values. 

    Note 1: I just found out that I can’t use pseudo-differential mode for (AIN2/3) because AIN3 is with 1.5V out of Spec.
    Note 2: There is an error in the data sheet. Is CH1_CH0_CFG at position 0 as in Figure 7-14 or Bit 6-7 as in Table 7-20? (green pen) 

    My input is as follows
    AIN0: measurement signal 0 [range 0 … 4V]
    AIN1: Offset ~ REFby2 (2V)
    AIN2: measurement signal 1 [range 0 … 4V]
    AIN3: Offset ~ 1.5V

    I use the internal reference.

     

    In single-ended (auto) mode (AIN_CFG=0 and AUTO_SEQ_CFG1=0b1111), I get the expected results. 

    With pairing AIN0 and AIN1 I have tried several combinations of AIN_CFG and AUTO_SEQ_CFG1, but without useful results.
    I assume that I need CH1_CH0_CFG = 0b10 and CH2_CH3_CFG = 0.

  • +1 in reply to Thomas Blocher
    TI__Expert 8545 points

    Hi Thomas,

    Thanks for pointing out the datasheet error, I will request an update. The large table is correct, that is, bit 7-6 is CH1_CH0_CFG[1:0].

    One thing to try, could you enable only CH0, CH2, CH4, CH6 in auto-sequencing mode when using input pairs? Let me know what the output looks like.

    Best regards,

    Samiha 

  • 0 in reply to Samiha Sharif
    Intellectual 475 points

    Hi Samiha! 

    Thanks for your answer. 

    I will use the single-ended (auto) mode for now; maybe I will implement the pseudo-diff mode later.