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Design Tips

Zubair Lutfullah
Intellectual 295 points

Other Parts Discussed in Thread: ADS1298, ADS1298R, TMS320C5515

Hello,

We plan on using the ADS1298E PDK Design as a reference for an actual product.

I would like to request some pointers on circuitry between the ADS1298 and patient contact electrodes. The current design is quite simple.

Is it usable as it is?

Points I noticed :

DC Blocking capacitors are marked Not Installed. There is space available to solder and test this. Analog DC blocking capacitors should be better right?

There is no Defibrillator protection. I believe that would involve diodes and some sort of lamps to redirect the energy. Correct?

I think the rest of the design can be used as it is with digital offset removal and a warning to not use any defibrillator when electrodes are attached. Correct?

Or am I missing some critical instrumentation issue.

Any help would be greatly appreciated.

Thanks

ZubairLK

  • 0
    TI__Mastermind 46290 points

    Hi Zubair,

    The ADS1298 evaluation kit is functional or usable with respect to evaluating the performance of the ADS1298 in ECG applications with a simulator. We have not included any protection circuitry on the EVM for connecting electrodes to a patient due to some legal implications.

    I will have to look into how much of this we are allowed to advise you on and get back to you.

  • 0 in reply to Kevin Duke
    Intellectual 295 points

    Thank-you very much.

    I will await guidance. I am not asking for specific advice.

    But a general direction to look towards to as I have no idea at the moment.

    Some standards document? Anything would be greatly appreciated.

    Regards

    Zubair

  • 0 in reply to Zubair Lutfullah
    TI__Mastermind 46290 points

    Zubair,

    Zubair Lutfullah said:
    Some standards document? Anything would be greatly appreciated.

    For legal reasons I am not allowed to share any of the standards documentation with you. These documents are copy-written by the institutions/organizations that maintain them and they require that you pay for the documentation.

    Zubair Lutfullah said:
    I would like to request some pointers on circuitry between the ADS1298 and patient contact electrodes. The current design is quite simple.

    Is it usable as it is?

    Yes, it is usable to evaluate the ADS1298 in ECG applications with a simulator.

    Zubair Lutfullah said:
    DC Blocking capacitors are marked Not Installed. There is space available to solder and test this. Analog DC blocking capacitors should be better right?

    There are footprints made available to populate a number of DC blocking capacitors on the ADS1298 and ADS1298R EVMs. They are marked not-installed because they do not come populated on the board from the manufacturer.

    Zubair Lutfullah said:
    There is no Defibrillator protection. I believe that would involve diodes and some sort of lamps to redirect the energy. Correct?

    There is an application report by our C55XX DSP team that goes into a bit of detail about defibrillator protection circuits. Hopefully this can help address some of your questions. See below for the relevant snippet from the document, refer to TI lit. number SPRAB36B (ECG Implementation on the TMS320C5515 DSP Medical Development Kit) for the full document.

    Zubair Lutfullah said:
    I think the rest of the design can be used as it is with digital offset removal and a warning to not use any defibrillator when electrodes are attached. Correct?

    This EVM should not be used on a patient. Only with a simulator.
  • 0 in reply to Kevin Duke
    Intellectual 295 points

    Hello Kevin

    I understand the limitations of your position.

    Thank-you very much for referring me towards TI lit. number SPRAB36B. I will check it out.

    If it is not too much of a bother, can you refer a part no to populate the DC blocking capacitor area?

    I checked the BOM. It says capacitor only.

    I'm a little new to this Biomedical area and am being super extra cautious..

    Regards

    Zubair

  • 0 in reply to Zubair Lutfullah
    TI__Mastermind 46290 points

    Zubair,

    A DC blocking capacitor in a biomedical application really shouldn't be any different than any other DC blocking capacitor. Just remember 1/jwC and choose a capacitance that gives very high impedance at near 0 hertz and low impedance at your frequency of interest. The ADS1298R EVM has some of it's DC blocking caps installed and uses 2.2nF.

  • 0 in reply to Kevin Duke
    Intellectual 295 points

    Thank-you very much.

    Regards

    Zubair