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ADS131M08: ADS131M08 multiple device reading

fabi
Prodigy 90 points
Part Number: ADS131M08

Hi!

I want to use 3 ADS131M08 to read simultaneous data from the 24 channel (8 channel per ADC) with 1 MCU. After reading the datasheet, I'm not sure if I should do this using 3 different SPI and connecting the SYNC/RESET pin between the 3 ADC to syncronize the reading or if I should use just 1 SPI bus for all 3 ADC.

I need to measure all 24 inputs in 500us max.

Thank you!

Fabiola

  • 0
    TI__Guru 62396 points

    Hello Fabi,

    Thank you for your post.

    Either one may work for your application, but each method has its advantages and disadvantages. Of course, a single SPI peripheral is easiest to route on the PCB. However, the amount of data to be transferred may limit the fastest supported data rate, depending on the available SCLK frequency in your MCU. You mentioned requiring 500 us maximum to read all the data, which puts the minimum data rate at 2 kSPS. Did you have an ideal target target rate in mind?

    Please tell us whether you plan to enable the CRC word, the word size setting, and the DVDD supply voltage you are using in your system. This will help us determine whether it is feasible to support 3 devices on a single SPI peripheral.

    Best regards,

  • 0 in reply to Ryan Andrews
    Prodigy 90 points

    Hi Ryan,

    Thank you for your reply. I don't have an ideal target rate in mind. My only prerequisite is to measure all samples in 500us or less.

    I'd like to enable the CRC word. The word size would be the standard 24bit and my DVDD is +3.3V.

    I have enough SPI on my MCU, so it wouldn't be a problem to use 3 SPI buses for the 3 ADCs. If this is the case, should I connect all SYNC/RESET pins together in order to achieve the simultaneous sampling?

    Best regards,

    Fabiola

  • 0 in reply to fabi
    TI__Guru 62396 points

    Hi Fabi,

    Yes, a SYNC pulse and a common master clock would be required to synchronize the conversions and /DRDY pulses from all 3 devices. 

    Regards,