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ADS8586S: Multi devices cs and rd pin

Luca Meloni
Intellectual 460 points
Part Number: ADS8586S 
Hello everybody. I need some information on the ADS8586S CHIP. 
I need tu use 3 devices in parallel  for have 18 channels. Can I connect all RD pins togheter,  and use 3 indipendent CS signals? If a device has the CS pin deasserted, is any pulse on RD pin  ignored?
Note: all START-CONV pins are connected togheter also.
Regards, Luca
  • 0
    TI__Mastermind 18900 points

    Hi Luca,

    Let me take a couple of days to get you an answer.

    Thank you,

    -Cole

  • +1
    TI__Mastermind 18900 points

    Hi Luca,

    In short, yes, the RD can be tied together and CS can be independent.

    I would just be a little careful on the routing and capacitance that might be created on that line if multiple devices are sharing the same signal. Its pretty common to put a resistor in series (e.g. 20 - 100ohms, 49.9 ohms typical) to help with the harsh edges that might be generated from switching them so I'd recommend putting a footprint for a resistor. Hopefully its not so bad you need a buffer in series with each.

    For a longer explanation, the falling edge of CS and RD/SCLK will activate the parallel serial bus logic so the RD/SCLK is effectively ignored until that happens. Like the datasheet says, the CS activates the bus and RD clocks out the data. So, the device communication bus won't be active without CS going first.

    Best,

    -Cole

  • 0
    Intellectual 460 points

    Tnx Cole!

    Now everything is clear.
Thank you very much