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ADS1298 documentation

Ariel Quezada
Prodigy 10 points
Other Parts Discussed in Thread: ADS1298, ADS1298ECGFE-PDK

Hi, I have been testing the ADS1298 for a while, and while reading the docuemntation, I found a couple of things, that I think are typos:

- In the official datasheet ( http://www.ti.com/lit/ds/symlink/ads1298.pdf ), on page 22, Table9, the reset value for the CONFIG2 register appears as 0x40, but reading the description of the CONFIG2 register on page 25, I think that the reset value should be 0x00.

- In the document "Improving Common-Mode Rejection Using the Right-Leg Drive Amplifier" ( http://www.ti.com/lit/an/sbaa188/sbaa188.pdf ), on page 7, there is a reference to "ADS1298ECGFE-PDK User's Guide", ( http://www.ti.com/lit/ug/sbau171c/sbau171c.pdf ), and in Figure 7, the input capacitors to the EVM are 47nF, but in the schematic on page 56 of the user guide document, the input capacitors are 47pF. ¿Which is the correct value?

Thank you and best regards,

Ariel Quezada

  • 0
    TI__Guru 66466 points

    Hola Ariel,

    Thank you for your feedback!

    1. The default value for CONFIG2 is 0x00. I will make a note to update this in the next datasheet revision.
    2. This one takes a little more explanation. These input low-pass filters are primarily used for anti-aliasing. Generally, they should be sized to give a cutoff frequency that is about two decades smaller than the modulator sampling frequency. The ADS1298 inputs sample at 512kHz in High-Resolution Mode and 256kHz in Low-Power Mode, so the input filters could be changed to give a cutoff in the range of 1kHz - 5kHz (i.e. C = 4.7nF). The digital filter in the ADS1298 has a -3dB passband of 0.262 x Data Rate, so the input filters do not have to be sized so large.

    Saludos,