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ADS8548: high precision DAS with +/-10v bipolar analog input range

Sanjeev Sarpal
Intellectual 490 points
Part Number: ADS8548
Other Parts Discussed in Thread: ADS8584S, ADS8588S, ADS1120, ADS1220, ADS1246, PGA280, ADS1146

Dear all,

We are looking into designing a relatively low speed DAS system for sensors measurement.

Our requirements are:

  1. 2 differential analog inputs (+/-10v max)
  2. Max 2k sampling rate (we'll be doing a lot of DC measurements too)
  3. Simultaneous sampling.
  4. Ideally PGA and sigma delta ADC (16bit)
  5. Ideally powered from a single supply (USB, +5v).

I noticed that the ADS8584S device is very suitable, as it runs on a single supply (of course, when it's avalaible). However, the SAR ADC and high sampling rate perhaps make it less suitable for low frequency measurement? The other option is to use two PGA280s with ADS1259s, but this would require a seperate bipolar analog power supply, external clock, and increase the board area which is undesirable. Do any of you have any ideas or know of a seperate AFE as implemented in the ADS85xS? Also, perhaps there are better alternatives to implement our application?


Thanks!

  • 0
    TI__Mastermind 44550 points

    Hi Sanjeev,

    The ADS8588S might be the best fit from the ADS85xxS family, as it's data rate is only 200kSPS.

    I don't think having the high-sampling rate is much of an issue for low-frequency measurements. Typically, the ADC's noise and power consumption will increase with the sampling rate, so as long as the ADC's performance is okay for your application I wouldn't be too concerned with the extra bandwidth. You can always implement a post-processing filter in software to provide extra filtering and reduce the bandwidth.

    On the delta-sigma ADC side, we don't have any parts similar to the ADS85xx that can directly connect to +/-10V; therefore, you'd need to provide either a higher voltage PGA (like the PGA280), or a resistor divider to scale the voltage to the ADC's input range. We do have delta-sigma ADCs with integrated (low-voltage) PGAs, that would be able to connect up directly to a resistor divider, such as the ADS1146 or ADS1120 (there are also 24-bit versions: ADS1246 and ADS1220). These parts are only single-channel, so you would need synchronize two of them to get simultaneously sampled data.

    Best Regards,
    Chris

  • 0 in reply to Christopher Hall
    Intellectual 490 points

    Thanks, Chris. We'll look further into this.


    Regards,

    Sanjeev.