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ADS1299 datasheet error - input mux

Simon Knopp
Prodigy 30 points
Other Parts Discussed in Thread: ADS1299

The ADS1299 datasheet (SBAS499A, Rev A) contradicts itself about the default value of the CHnSET registers. 

  • In Table 11, the default value of CHnSET is given as 0x61. This is correct.
  • On page 44, the default value of the MUXn[2:0] bits of CHnSET are given as 000 (normal). This is incorrect. It is actually 001 (input-short). 

I've reported this via the documentation feedback link in the PDF, but I thought I'd report it here in case anyone else got caught out by it. 

  • TI__Guru 66446 points

    Hi Simon, 

    Thanks for your input, we have noted the change. CHnSET = 0x61 (input short) is the correct Device Default.

    For those using the ADS1299EEG FE:

    The firmware overwrites the ADS1299 Device Defaults once the demo kit is connected and the PC software is running. In addition to a couple other registers, this affects the CHnSET registers. The Programmed Defaults for CHnSET is 0x60 (normal electrode input).

    The user can restore the Device Defaults by selecting the corresponding Reset Mode under the ADC Register tab, followed by clicking the "Reset" button above.

     

    Regards,

  • in reply to Ryan Andrews
    Prodigy 60 points

    I also have a question about a discrepancy in the ADS1299 datasheet.  In Figures 27 and 28 on page 22, the gain vs normalized frequency response of the decimation filter is shown for different possible output sampling rates.  In Figure 27, the slowest output sampling rate is shown as a blue line where DR[2:0 = 110].  The filter responds for this sampling rate reaches -160 dB at a normalized frequency of ~0.05.  The fastest output sampling rate is shown with a red line where DR[2:0] = 000.  The filter responds for this sampling rate levels out with harmonics around -110 dB.

    Figure 29, shows the output for the same two sampling rates, extended for a normalized frequency = 4*fmod.  This figure does not have a legend, and the responses of the two output sampling rates is reversed from the response shown in Figure 27.

  • in reply to Troy Thielen
    TI__Guru 66446 points

    Hi Troy, 

    The use of color was not kept consistent between these plots. In Figure 29, DR[2:0] = 110 is in Red, and DR[2:0] = 000 is in Blue.

    I'll make a note to include a legend in a future datasheet revision.