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Hardware Pace Detection circuit For ADS1298

Mangesh Jadhav
Prodigy 100 points
Other Parts Discussed in Thread: ADS1298

Hi,

    This is Mangesh and I am working on ADS1298 for new ECG device development. I just read that it has hardware as well as software pace detection. I have chosen to go for hardware pace detection. But I dont have external hardware for Pace detection. Please give me the circuit for Pace detection. I have understood the procedure to do the same from datasheet. Please reply soon.

  • 0
    TI__Mastermind 43915 points

    Hi Mangesh,

    A couple of ideas have been tossed around regarding PACE detection both in the forums and when we talk with customers. The truth is, the PACE detection circuit and hardware is going to be dependent on the design itself. Certain applications are interested in the details of the PACE signal which require that the signal is taken from the PACE_OUT lines on the ADS1298, bandpass filtered to remove the ECG components and higher frequency noise, and routed into a SAR converter to digitize. Other design ideas have included simply looking to see if a pacemaker is present where a bandpass filter and maybe a comparator could be used. The pacemaker bandwidth is 10x to 100x greater than the ECG bandwidth so you are looking for two separate components from the input signal.

    Regards,

    Tony Calabria

  • 0 in reply to Tony Calabria
    Prodigy 100 points

    Thanks Tony !

                 As mention above there are two purposes of pace detection. But I will be more interested in later part. I just want to identify whether Pacemaker is present or not.

    So can you  please provide comparator circuit for the same .

  • 0 in reply to Mangesh Jadhav
    TI__Mastermind 43915 points

    Hi Mangesh,

    The actual design of the circuit is going to vary from design to design. The Pacemaker frequency components are not the same from patient to patient making it difficult to have a narrow band filter to find the PACE signal. You will need to place a high pass filter, followed by a comparator set to a specific threshold depending on the design. The result from the comparator will need to be latched somehow so that you have time to read it back using either an ADS1298 GPIO or micro-controller. The difficulty is going to lie in making sure you do not register a 'false' pace signal. Some frequency components associated with muscle activity lies within the same bandwidth as some pace signals. For that reason, a lot of pace detection circuitry uses a HPF followed by a wide bandwidth converter capable of digitizing the pace signal to verify that it is actually there. You can try using a HPF and comparator to see what kind of results you see but I cannot guarantee itll be as accurate as using a wider bandwidth ADC.

    Regards,

    Tony Calabria