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ISO7731: Propagation delay specs

Part Number: ISO7731

Hi,

    I have been looking at the ISO7731 propagation delay specs and have a question about it.

The tPZH and tPZL are listed as 3us to 8.5us on page 12 section 6.15 Switching Characteristics - 5V supply. Should that spec read as 3ns to 8.5ns? How can those specs be in us if this part is rated as 100Mbps.

Thanks,

Ram.

  • Hi Ram,

    Sorry for the confusion. Thanks for asking on E2E!

    The 3us and 8.5us refer to enable propagation delay. This is the delay from when the enable pin is turned off or on until the device is enabled or disabled.

    The channel propagation delay (TPHL, TPLH) is 11ns typical - which is what I believe you are looking for. 

    Does that clear it up for you? 

    Best regards, 

    Dan

  • Hi Dan,
    Thanks for your response. I am assuming that Channel propagation delay is when the power is applied and Enable pin gets pulled to 3.3V or 5V. During normal mode of operation, the Enable pin will be at 3.3V or 5V and hence doesn't matter. Am I correct in my assumption?

    Can you clarify that this part can be used for Vcc1 = 3.3V and Vcc2 = 5V as there was no specific table addressing the timing and power requirements for this situation.

    Thanks,

    Ram.
  • Hi Ram,
    Yes exactly - your understanding is correct.
    And yes, Vcc1 and Vcc2 are independent and so it is not an issue to power Vcc1 = 3.3V and Vcc2 = 5V. Unfortunately, there is not a specific table in the datasheet for this configuration.
    Best regards,
    Dan