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ADS7223: USING multiple ADS7223

Stuart Rumley
Prodigy 250 points
Part Number: ADS7223
Other Parts Discussed in Thread: ADS8586S, ADS8588S, AMC1100, ADS7253

I need to monitor voltage and current on high voltage 3-phase ac line circuits.  Therefore, I would like to use three separate ADS7223 to make three dual simultaneous reading (2x3=6).  I only have one 4-wire SPI buss available (BeagleBone Black) but I do have individual GPIO that can be used for device selection.  My sample (conversion) rate is 500us (0.5ms).

1. Is this possible?

2. What connections to SPI bus need to be made?

3. What mode is best for this operation?

4. Is the ADS7223 the best choice for this application? 

  • 0
    TI__Expert 5485 points

    Hi Stuart

    Thanks for sharing design details. I would recommend you to take a look at ADS8586S. It is 16bit, 6 channel, 200ksps simultaneous sampling SAR ADC specially designed for applications such as protection relays, power grid monitoring.

    You can go through device details here

    Please let me know if this device looks ok for your application

    Thanks & Regards

    Abhijeet

  • 0 in reply to Abhijeet Godbole
    Prodigy 250 points

    Thanks for that.  The ADS8588S is a possibility and I'll take a closer look but I see it doesn't have differential inputs.   Any other recommendations or is there a way to use the ADS7223?

    Thanks,

    Stuart

  • 0 in reply to Abhijeet Godbole
    Prodigy 250 points
    Abhijeet. I'm using the AMC1100 isolation amplifiers in this application. I noticed in the AMC1100 datasheet it shows what looks like a 4-channel differential ADC. Can you tell me what that part is?
    Thanks,
    Stuart
  • 0 in reply to Stuart Rumley
    TI__Expert 5485 points

    Hi Stuart

    If differential sensing is mandatory requirement then you can use 3 x ADS7223 in following way

    When CS is held high SDO pin is in high Z state. This should allow you to short SDOA and SDOB data outputs of each ADS7223 together. You can use either CONVST or CS to enable the device conversion. Please refer to timing diagram shown in datahseet for more details.

    Based on your prefered mode selcection (Manual or Auto) you can set pin M0 and M1. (Please refer to table 5 of datasheet for more information)

    I would like to recommend you to take look at ADS7253 too. It is 12 bit SE/Psuedo diff input simultaneous sampling, 1MSPS SAR ADC. This device has no CONVST pin and you should be able to select individual device through CS. This will no of GPIO required from host controller.

    Please let me know if you need additional details on this

    Thanks & Regards

    Abhijeet

  • 0 in reply to Stuart Rumley
    TI__Expert 5485 points

    Hi Stuart

    AMC1100 is precision isolation amplifier. It has differential input (Max allowed swing is +/-250mV) which is fed to delta signma modulator. Output of delta sigma modulator is transmitted differentially to output. This device has capacitive isolation between input and output. At output data is gained and filtered to give analog output.

    Isolation between input and output grounds actually enables device to be used in AC sensing. 

    I hope this answers your question

    Regards

    Abhijeet