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ADS7863A: Operation of two ADS7863A with SINGLE SPI interface

Dipen Dalal
Prodigy 45 points
Part Number: ADS7863A

My question is regarding the SPI configuration while using the two ADS7863A (http://www.ti.com/product/ADS7863A) with SINGLE SPI. The questions are listed below.

I would like to use two ADS7863A ADCs in automatic mode. I would like to have these two ADCs operate on a SINGLE SPI and want to achieve simultaneous sampling on all the eight analog inputs.  

1. Can I achieve simultaneous sampling on all the 8 differential channels of the two ADCs?

2. I will use a single channel (i.e SDOA) for the data output on each of these ADCs. I can use the CS to enable SDOA output for one of the ADCs and perform read from this ADC; at this point the SDOA output for the second ADC remains in the three-state. After this I would enable the second ADC through CS and read it. In this case do I read the data which was already sampled simultaneously?

3. What happens when the ADC output is in three state mode? Is the ADC on halt or it still keeps performing conversions on each CONVST (I have one CONVST and RD for both the ADCs)..? How to mange the ADC operation with a single CONVST and RD signal for both the ADCs?

4. Can someone please suggest me an overall picture of how this two ADCs can be configured on a single SPI?

I want to use the schematic from Fig. 42 in ADS7863A datasheet. The SPI interface is provided by a TI DSP F28379D.

I would very much appreciate any help on this topic.

Thanks 

- Dipen 

  • 0
    TI__Guru 59836 points

    Hello Dipen,

    Thank you for your post.

    Simultaneous sampling can be achieved so long as the interface inputs are shared (i.e. CONVST, RD, CLOCK, etc.). 

    The interface configuration will depend on the overall throughput you are aiming for and the maximum CLOCK frequency you have available. Just to confirm, you are looking to measure 8 differential input simultaneously in Automatic mode (M0 = 1)? Do you have a preference to use a single SDO or two SDOs per device (there may not be an option here depending on desired throughput)?

    Best regards,