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ADS1194 / ADS1294 help required

Jamal Ahmad
Prodigy 20 points
Other Parts Discussed in Thread: ADS1298, ADS1294

Hello,
           I am a final year BEE student and i plan to use either the ADS119x / ADS129x analogue front ends for ECG signal acquisition.
I did go through the data sheet but also kinda got lost in it (because of the sheer amount of info in it). So if someone could direct me i would really appreciate it. Sometimes knowing what not to do can get the job done quicker.
If someone would be willing to share a schematic for ADS119x / ADS 129x excluding the MCU then i would even more grateful.

  • 0
    TI__Mastermind 18285 points
    Jamal,

    I'm moving your post to the precision data converter forum. They will be better equipped to answer your questions on this device.
  • 0
    TI__Mastermind 38745 points
    Hey Jamal,

    The user's guide for the ADS1298 EVM has a useful schematic at the end (www.ti.com/.../sbau171c.pdf). The ADS1298 is identical to the ADS1294 except with 8 channels instead of 4. The schematic is for an evaluation platform, though, so there may be certain things you'll find you don't need. If you don't understand something, look to the datasheet for further explanation of how it works. If you still don't understand it, feel free to post here and we'll try to answer your question.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    Prodigy 20 points

    Hello Brain Pisani,

    Thank you for the quick reply. The schematic is pretty helpful; i guess I'll have more questions when the device finally arrives. I do have 2 questions right now though.

    1-Regarding the SPI pins and the GPIO pins.
    what is the purpose of the GPIO pins? SPI already is present for data communication to an MCU!

    2- Is it a must to separate the analogue and digital power-lines and grounds or can they be tied to one another without much consequence?

    Regards,
    Jamal Ahmad

  • 0 in reply to Jamal Ahmad
    TI__Mastermind 38745 points
    Hey Jamal,

    1. The GPIO pins are just that - General Purpose I/Os. You can use them for any purpose you'd see fit. The intention was to provide some extra flexibility if GPIO pins are scarce on your microcontroller.

    2. It depends. If your chip has separate positive supplies, you're going to want to guarantee that whatever current flows out of one source flows back where it came from. That is to say, your layout must be such that the path for current is clear for both analog and digital ground current. Another concern is transient digital noise affecting analog inputs/power supplies. This can generally be solved by placing decoupling capacitors close to the pins such that a small "loop" is formed for transient signals at the power supply pins. Even so, you may not want to have your digital return current path flow directly beneath analog circuitry.

    Regards,
    Brian Pisani