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TLC2543QDWREP

Peter Matamala
Prodigy 10 points
Other Parts Discussed in Thread: TLC2543

We use the TLC2543 in several of our system and we just had a system returned from the field; when tested in house, we noticed the converter was reading approximatly 2x the voltage of the analog inputs; ALL the inputs showed the same problem; after the first day of  testing the system has been operating normally.

My question

1. what kind of failure can cause  the converter fail in  this mode 

  • 0
    TI__Guru* 93745 points
    Peter,


    I'm checking to see who normally supports this product. Since this is a High Rel device, there is some question about who takes these questions.

    I don't know this device or its history of possible failures, but I would guess that there may be some sort of error in the sampling of the reference involved. Imagine that the ADC is a comparison between the input and the reference. If the reference is somehow sampling half of the charge that it normally would, then the input would appear twice as large as expected.

    Do you work with a distributor for your parts? I believe they would normally handle these type of problems and returns.


    Joseph Wu
  • 0 in reply to Joseph Wu
    TI__Expert 4405 points

    Peter,

    Two possibilities come to mind:

    1. First, as Joseph mentioned, all analog inputs showing twice the voltage seems to indicate that there might be a problem with the Reference.

    - How is the reference generated and driven in your system? What were the values at Vref+ and Vref- during the fault condition? You might want to try powering up the system a few times and see if the reference comes up at an incorrect value.

     - The TLC2543 has an useful test-mode feature that allows you to measure the reference voltages itself (see Table 4 on page 18 of the datasheet). What were the reference voltages reported by the device when the inputs were showing double the voltage?

    2. Another less likely cause for this failure could be marginal timing that causes the DATA OUT to be captured one clock edge too early, appearing to read 2x the actual voltage. A quick scope capture should help resolve this.

    Hope this helps.

    Regards,

    Sandeep