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ADS1298 Sampling and Datarate

HARISHA BS
Intellectual 500 points
Other Parts Discussed in Thread: ADS1298

Hi,

For capturing pace maker pulses of 0.5ms duration, what is the recommended Data Rate settings for ADS1298 in LP mode? And in turn what will be the sampling frequency?

Regards,

Harish.

 

 

 

  • 0
    TI__Mastermind 38745 points

    Hey Harish,

    If you think of a pacemaker pulse as an ideal square pulse, it looks like a sinc function in the frequency domain. For a 0.5 ms duration pulse, the first lobe of spectral density falls under 2 kHz and the second comes in under 4 kHz. The ADS1298's fastest sampling frequency is 16 kSPS in LP mode. With the digital filter's magnitude response, this gives you a maximum bandwidth of about 4.2 kHz. It might be tough to get a good representation of the pacemaker pulse with this bandwidth limitation.

    However, the ADS1298 has two configurable analog pacemaker output pins that will output a single ended version of one of the channel inputs conveniently for a discrete detection methodology. TI has two TI designs that cover pacemaker detection with the ADS1298:

    • Software Pacemaker Detection which uses a buffer and a fast sampling SAR converter to convert a pacemaker signal on a separate, faster channel to be analyzed by your DSP or microcontroller
    • Hardware Pacemaker Detection which utilizes a differentiator and an SR latch to signal a processor when the detection has occured

    Let me know if you have questions about these.

    Regards,

    Brian Pisani

  • 0 in reply to Brian Pisani
    Intellectual 500 points

    Hi,

    Since you mentioned sampling frequency as 16KSPS. please can you clarify difference between Sampling frequency and Data rate?

    To my understanding if the data rate is 16KSPS we will be sampling at  256KSPS internally in LP mode. can you confirm this?

    Regards,

    Harish.

  • 0 in reply to HARISHA BS
    TI__Mastermind 38745 points
    Harish,

    You are correct. I should have been more careful with my terminology. The modulator samples the input at 256 kHz but the output is decimated according to the oversampling ratio to be output at the frequency specified by the data rate. In your case, that is 16 kSPS.

    Brian