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ISO1410: Communication failed during test

CHEN YAN
Intellectual 1430 points

Part Number: ISO1410

Hi, expert,

My customer encounters an issue when measure ISO1410 output data, they found the R pin will be pulled down for a short time when use the probe to measure it. Could you please help analysis this issue? Thanks.

Best Regards.

Chen

  • 0
    TI__Guru 57455 points

    Hi Chen,

    Thanks for reaching out.
    Could you please provide a higher resolution image of the waveform you have shared?
    Can you please also request customer to monitor both input (either A-B or A & B separately) and output (R) in one waveform to better compare and share the same with us?

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Intellectual 1430 points

    Hi, Koteshwar

    The clear waveform is as following,

    CH1: A

    CH2: B

    CH3: R

    Best Regards.

    Chen

  • 0 in reply to CHEN YAN
    TI__Expert 3482 points

    Chen,

    Thank you for providing the waveforms as requested!


    The provided waveform shows that the output (R) is in the mid-rail, which implies that the output (R) is disabled and in a high impedance state.

    Could you please ask the customer to observe the RE bar/DE signal?

    Please request the customer to capture the RE bar/DE, A, B, and output (R) in one waveform and share them with us.

    Regards,

  • 0 in reply to Alfred Chong
    TI__Expert 3482 points

    Chen,

    I hope you have resolved your customer's issue by observing the RE bar/DE signal.

    Please feel free to reach out to us if you have other questions.

    Regards,

  • 0 in reply to Alfred Chong
    TI__Intellectual 1430 points

    Hi, Alfred,

    Sorry for the delay, could you please help analysis below waveforms? Thanks.

    CH1 : EN

    CH2: R

    CH3: A

    CH4: B

    Best Regards.

    Chen

  • 0 in reply to CHEN YAN
    TI__Expert 3482 points

    Hi Chen,

    Thank you for sharing the waveforms.

    We can clearly see that the output(R) becomes high impedance when the ENABLE signal

    went from low to high. This is because the output(R) only turns on when the ENABLE signal

    is a logic low.

    Regards,

  • 0 in reply to CHEN YAN
    TI__Expert 3482 points

    Hi Chen,

    Thank you for sharing the waveforms.

    We can clearly see that the output(R) becomes high impedance when the ENABLE signal

    went from low to high. This is because the output(R) only turns on when the ENABLE signal

    is a logic low.

    Regards,

  • 0 in reply to Alfred Chong
    TI__Intellectual 1430 points

    Hi, Alfred,

    I'm sorry that you may misunderstand customer's question, the question is when they use probe to measure R, R pin would drop to GND for a while, please see the zoomed waveforms.

    Best Regards.

    Chen

  • 0 in reply to CHEN YAN
    TI__Intellectual 1430 points

    Hi, Alfred,

    Actually we can see from the test results, every signal goes OK, but they found the software can't read R signal when the probe add to the R pin, should they use special probe to measure R signal or should the add some external circuit to test R signal? 

    Best Regards.

    Chen

  • 0 in reply to CHEN YAN
    TI__Expert 3482 points

    Hi Chen,

    The R signal drooped because it was disabled. When Output(R) was in high impedance state, no current flowed to the output.

    The output(R) could only maintain its state with the amount of charge that has been stored at the output(R).

    When the customer probed the output(R) with 1M ohm resistance, the charge/current leaked through the probe.

    Hence, the output(R) could not maintain its voltage. In order to ensure a logic high when the output(R) is in

    high impedance state, please add a pull-up resistor of 4.7k ohm to the output(R).

    Regards,