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TRS3222: ROUT signal rise/fall time

Karen Perez
Prodigy 210 points

Part Number: TRS3222

What is the expected output rise and fall time for the ROUT pins of the transceiver?

Currently get 21ns rise time and 16ns fall time. Is that correct? I have a spec of <15ns.

Please advise.

Thank you

Karen

  • 0
    TI__Mastermind 25705 points

    Karen,

    TRS3222 works with 250kbps data rate. You mentioned 15ns. Is it the spec of the device or of the system? The rise/fall time of ROUT pin depends on the load of the pin, however usually it's not critical in the communication.

    Regards,

    Hao

  • 0 in reply to Hao L
    Prodigy 210 points
    The communication is working but I am characterizing the buses on the board. For this signal, the GPIO specs of the processor the signal transmit to specs <4ns at CL=30pF Vcc>=2.7V. I am wondering why the large discrepancy from the transceiver?

    I understand it depends on the load of the pin but do you have any tolerances and rise/fall time specifications for a specific loading to reference?

    The 15ns I believe comes from the UART specs but I have not verified that.

    Thank you,
    Karen
  • 0 in reply to Hao L
    Prodigy 210 points

    Hao,

    Any comments or updates to my previous response?

    Thank you,

    Karen

  • 0 in reply to Karen Perez
    TI__Mastermind 25705 points
    Karen,

    I'm sorry I thought I replied but it looks I didn't. Do you know why GPIO has <4ns requirement? It looks pretty fast for a less than Mega bps data rate (Actually 4ns rise time is equivalent about 100MHz bandwidth).
    www.edn.com/.../Rule-of-Thumb--1--The-bandwidth-of-a-signal-from-its-rise-time

    I'm sorry we don't characterize receiver's tr/tf for this device. The output is a push pull structure, whose impedance work with the load to govern the rise/fall time. I'm afraid the variation might not be as tight as you expected due to the nature of slow transmission. Please let me know if you have more questions.

    Regards,
    Hao