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Best ADC for low latency control application (and DAC)

Im working on a project which is a controller in the acoustic frequency range (DC-20kHz); latency is very important.

I built a prototype with an AD1933 DAC and an ADC from another manufacturer; both are sigma delta and have added latency from the digital filters in the chips (I chose them because of dynamic range).  The overall group delay from both filters was about 50/fs, which is much too high for my application.

What would be an optimal ADC (and DAC) product from Analog Devices for such applications; audio frequency range where low latency is more important than dynamic range?

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  • Raman,

    Can you provide a bit more detail about how you've specified required latency through your entire system and how you've distributed that (budgeted it) for each component ADC, PROCESSOR, DAC.   If the details are sensitive let me know and I can try and setup a direct call with you to sort out the details.   I'm assuming you're probably looking for a total system latency <5uS if not better but if you can confirm that will certainly help.  

    Also any details about your transducers would be helpful as well in making recommendations for the system.  Specifics on impedance and voltage/current range for both input and output would help set limits on the potential solutions.

    Thanks for choosing Analog Devices.

    Sean

  • Hi Sean,

    This is for vibration control application.  Ideally I want to control as high in frequency as I can; the lower the delay the higher in frequency I can control.  I dont have a specific time that I want to meet; my goal here is to see how low I can get the delay, and to build a prototype with said parts.  I am investigating to see if a controller with this architecture would be feasible and for what applications it would be useful (usefulness determined by the overall delay)

    The control loop is running on the FPGA interfacing with the ADC/DAC and adds a 1 sample (at fs of ADC/DAC) delay. Aside from this, the only delay will come from the ADC/DAC.  With the sigma/delta ADC/DAC Im using, my delay is ~500us (50/fs with fs=~100kHz), almost all coming from the digital filters in the Sigma/Delta chips.  This is far too high to be useful for most of the intended applications.

    Transducers are going to be accelerometers, but I guess more generally a piezoelectric sensor that is powered by a separate constant current power supply (IEPE standard).  I will bias/scale the analog +-5V output from the transducer to whatever range the ADC needs with separate circuitry; I am not too worried about that.

    The DAC will also have circuitry to bias/scale the output to drive the actuator being driven.

    At this point this is completely in a research and prototype stage; and it seems I need to trade off some of the dynamic range the sig/delta chips offer for something with lower latency.  That is what I am asking for a recommendation on.

    Thanks

  • Raman,

    Let me give you a couple of suggestions to start with to have you review and you can always come back for further help reducing the list.   I'm going to make the assumption here that this is a multi-channel application so I've eliminated single channel devices from my list.   There is a mix of simultaneous sampling and multiplexed devices here so we'll need to refine the system requirements a bit more to allow us to narrow the selection but have a look and let me know how you want to proceed.

    Simultaneous Sampling

    AD7606C-18

    LTC2358-18/16

    AD7386

    Multiplexed

    AD7689

    AD4696

    Sean

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  • Raman,

    Let me give you a couple of suggestions to start with to have you review and you can always come back for further help reducing the list.   I'm going to make the assumption here that this is a multi-channel application so I've eliminated single channel devices from my list.   There is a mix of simultaneous sampling and multiplexed devices here so we'll need to refine the system requirements a bit more to allow us to narrow the selection but have a look and let me know how you want to proceed.

    Simultaneous Sampling

    AD7606C-18

    LTC2358-18/16

    AD7386

    Multiplexed

    AD7689

    AD4696

    Sean

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