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ADS1258 Minimum width of START

Todd Anderson78572
Guru 14640 points

Other Parts Discussed in Thread: ADS1258

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I have looked for minimum start pulse width on datasheet - cannot find it. Can someone help?

  • 0
    TI__Guru** 101175 points

    Todd,


    That's a pretty good sized omission from the datasheet. I'll look through what I have to see if I can find an answer, if I can't find it, I'll track it down through the design group.


    Just a warning - it may take a little time to pull out this information.

    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Guru** 101175 points

    Todd,

    I managed to find the digital section of the device to look at the START pin and how it is used in the ADS1258.

    It looks like it is latched into the master clock domain within pulses of the master clock and then is used as a reset to start a new conversion through a couple of other digital building blocks. I'd say that the answer is probably that the minimum START pulse width is 2 tCLK periods, but let's extend that to 4 tCLK periods in case I've missed something.

    I've even had a chance to test the min pulse width on the using the ADS1258EVM and it's pretty close to what I expected. With 2 tCLK periods, I did not find any cases where the conversion start failed. However, I'm still going to recommend 4 tCLKs. In the case of a 16MHz clock, this time period would be 250 ns.

    Joseph Wu