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ADS1247: ADS1247 floating CLK input

Phil Clark
Prodigy 60 points
Part Number: ADS1247
Other Parts Discussed in Thread: TIPD152, , TIPD120

Hello,

I just had quite a few boards made using the ADS1247. Referring to the TIPD152 reference design, I didn't ground the CLK input. (Didn't realize that the data sheet says to ground this pin to activate the internal oscillator until it was built.) The TIPD152 reference design does work doesn't it? Is the floating CLK input on the TIPD152 reference design an acknowledged error? Should I spend the money to have all of these boards haywired so that the CLK input is tied to ground?

Thank you!

Phil

  • 0
    TI__Guru* 92715 points
    Phil,


    A similar question about the ADS1247 was answered here:

    e2e.ti.com/.../481170


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 60 points
    Thank you for the response Joseph. It says "Access Denied" when I click on that link. I am logged in to TI website...
  • 0 in reply to Phil Clark
    TI__Guru* 92715 points
    Phil,


    Sorry about that. It was in an internal forum that has since been shut down.

    There were two responses from different TI engineers. The first response stated: "The CLK input on ADS1247 could be left floating but it is advisable to tie the CLK pin to DGND."

    The second response stated: "As emphasis to the advisement, any noise on the CLK pin from EMI/RFI when it is floating will place the device into external clock mode. Once it is in the external clock mode the only way to place it back into the internal oscillator state is to power cycle the device or by toggling the RESET pin. Even though the CLK pin has a Schmidt input, glitches have been known to happen with customers leaving it float. I very highly recommend that the CLK pin be tied to DGND as this will ensure that the ADS1247 will always be using the internal oscillator."

    These were given for the ADS1247 used in TIPD120.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 60 points
    OK great. That answers my question. Thank you for the quick response!

    Phil