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ADS1192 - the hardware pace using slope detection

Hirotaka Matsumoto
Guru 27525 points
Other Parts Discussed in Thread: ADS1192, ADS1298, ADS1194, OPA320, ADS7042, OPA348, TLV3401, ADS1293

Hi all

Would you mind if we ask ADS1192?

The following URL shows "the hardware pace using slope detection"
http://www.ti.com/lit/ug/slau511/slau511.pdf

On this document, ADS1298 is used for.
So is it possible to use ADS1192 instead of ADS1298?
And if it is possible, in this case,  could you let us know how PGAnP and PGAnN connect to?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Mastermind 38745 points
    Hello Matsumoto-san,

    This functionality is unavailable on the ADS1192 because there are no internal PACE buffers. Any pacemaker detection with the ADS1192 will have to be done in the digital domain.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    Guru 27525 points

    Brian san,

    Thank you for your reply!

    OK, we recommend that our customer use ADS1298 in this case.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Mastermind 38745 points
    Matsumoto-san,

    A closer fit to the ADS1192 is the ADS1194 since is has half the number of channels versus the ADS1298 and provides 16 bit data. It also has internal pacemaker detection buffers. I'm not sure what your customer is looking for, but that may provide better value.

    Brian
  • 0 in reply to Brian Pisani
    Guru 27525 points

    Brian san,

    Thank you for your prompt reply and your kindness!

    Our customer is looking for lower Power Consumption the same as ADS1192.
    ADS1298 and ADS1194 is much Power Consumption compared with ADS1192.
    (As the function, ADS1298 and ADS1194 accommodates for our customer demand.)

    So, with having the external pace buffer circuit(using OP amp), is it possbile to use ADS1192?

    And if you have some reference pace buffer circuit, could you give us it?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Mastermind 38745 points
    Hello Matsumoto-san,

    It is possible to detect a pacemaker pulse with a discrete circuit. In fact, I'm currently working on a reference design to that effect which, unfortunately, will likely not be published for at least a couple months. I can give some insight though. The ADS1298 pacemaker buffer provides single ended to differential conversion, but such functionality can be achieved with nearly any operational amplifier. This is necessary if you'd like to take a typical ECG lead, which is differential, and make it one signal measured with respect to ground. In addition, you can use the op-amp to provide a gain stage or buffer anti-aliasing filters. The key parameter when picking the op-amp for pacemaker detection in bandwidth. The pacemaker pulse is very narrow and thus has wide spectral content. In some cases you may need as much as 10 kHz for the signal itself. If the intention of your customer is to convert the pulse and process it digitally, you will also need a wide-bandwidth ADC - which then pushes the required bandwidth for the op-amp further.

    For my application, I chose an OPA320 since it has a very wide bandwidth and high input impedance. In my application, I chose to convert the signal to digital and process from there. For the ADC, I used the ADS7042, which was chosen for its wide bandwidth. If your customer is looking for a discrete analog solution, there is a reference design here (www.ti.com/.../slau511.pdf) that uses a comparator and a latch to detect a pulse. The only change that would need to be made would be to add your own op-amp at the front end instead of using the ADS1298's internal PACE buffer. Let me know if you have questions about this.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    Guru 27525 points

    Brian san,

    Thank you for your very kind reply!
    We could almost undestand, but we have a few questions.

    <Question1>
    Our customer would like to detects ECG and PACE using ADS1192.
    That's why, our customer would like to use ADS1192 because of low current.
    PACE signal is as much as 10 kHz, the PGA Bandwidth of ADS1192 is 8.5kHz.
    So, it does not satisfy with 10kHz, does it?

    <Question2>
    If Question1 is no matter, we guess that the system layout will be the following;

    -System layout>
    ADS1192 -> PGAXP and PGAXN -> External instrumentation amplifier(change from differential to single ended) -> Buffer amp -> AC coupling
    -> P16 Vpace(www.ti.com/.../slau511.pdf) -> OPA348(rejection of ECG) ->TLV3401 -> PACE_OUT
    (External instrumentation amplifier and the Buffer amp are used for OPA348.)
    Is our recognition correct?

    <Question3>
    If ADS1192 isn't used for ECG + PACE detection, we will recommend ADS1293.
    ADS1293 consumption current is equal to ADS1192' one.
    How about it?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Brian Pisani
    Guru 27525 points

    Brian san,

    Thank you for your very kind reply!
    We could almost undestand, but we have a few questions.

    <Question1>
    Our customer would like to detects ECG and PACE using ADS1192.
    That's why, our customer would like to use ADS1192 because of low current.
    PACE signal is as much as 10 kHz, the PGA Bandwidth of ADS1192 is 8.5kHz.
    So, it does not satisfy with 10kHz, does it?

    <Question2>
    If Question1 is no matter, we guess that the system layout will be the following;

    -System layout-
    ADS1192 -> PGAXP and PGAXN -> External instrumentation amplifier(change from differential to single ended) -> Buffer amp -> AC coupling
    -> P16 Vpace(www.ti.com/.../slau511.pdf) -> OPA348(rejection of ECG) ->TLV3401 -> PACE_OUT
    (External instrumentation amplifier and the Buffer amp are used for OPA348.)
    Is our recognition correct?

    <Question3>
    If ADS1192 isn't used for ECG + PACE detection, we will recommend ADS1293.
    ADS1293 consumption current is equal to ADS1192' one.
    How about it?

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Mastermind 38745 points
    Hey Matsumoto-san,

    I wouldn't necessarily route the pacemaker signal through the ADS1192. I would instead simply have the inputs to to the ADS1192 strictly for ECG testing and also have them go the the circuit I recommended as a separate "pace channel". That way you can get around the bandwidth limitation of the ADS1192.

    It does look like the ADS1293 has some pace detection electronics, but I do not cover that device's support so I'm not the best person to ask about that part. I recommend starting a new thread with "ADS1293" somewhere in the title and you will get your questions answered about that device.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    Guru 27525 points

    Brian san,

    Thank you for your updata!
    OK, in case of using ADS1192, we suggest that our customer makes the separate "pace channel".

    And then,  when we use ADS1293, we make new thread.

    Kind regards,

    Hirotaka Matsumoto