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ADS1299 and C2000 - Dual supply, common ground?

José Jair Alves Mendes Júnior
Intellectual 460 points
Other Parts Discussed in Thread: ADS1299

So, I am trying to make a "portable" system to ads1299. I am going to use it with c2000 micro processor.

The following schematic (nice drawing skills ahead) shows how I intend to connect them.

The thing is, I remember reading somehwere here in the forums that it would be a good idea for both microprocessor (c2000) and ADS1299 to have the same ground. Although, I can't do that with this schematic (I suppose).

Will it work without having both grounds connected or should I go to a different approach to get the +- 2,5 where I can have a common ground?

Thanks.

  • 0
    TI__Mastermind 38745 points
    Hey JJ,

    The ADS1299 and the C2000 should share a digital ground so that the interfaces are at the same level.

    I would probably go with a different approach for this design. First, I would step the battery voltage down to 5 V (I would probably use a switching DC-DC though for power conservation purposes). Then I would use an inverter to create -5 V and then use two linear regulators to convert the +/- 5V to +/-2.5V.

    In fact, figure 60 in the ADS1299 EVM User's Guide has a schematic for how we create +/-2.5V on the EVM from 5 V. If you take that design, then you'll just need a buck to take you from 9V to 5V. I'm not a power expert so I wouldn't want to give a recommendation, but the people in the Non-Isolated DC-to-DC forum should be able to help you (e2e.ti.com/.../) if you tell them the voltages you need and the current you need to source. It is important, though for the switching converter avoid the ADS1299's modulator frequency, 1.024 MHz, and all integer multiples of that frequency since any noise around those frequencies will alias to the passband.

    Alternatively, the TI WEBENCH design tool is great for power designs: www.ti.com/.../overview.page

    Regards,
    Brian Pisani