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ISO7742: Enable propagation delay

Kazuki Itoh
Genius 10185 points
Part Number: ISO7742

Hi team,

My customer is conducting device functional test for ISO7742 (non-F).

They are testing it so the output transition is high-Z to H to L.

My customer found that the Z to H takes several tens of ns,
but the H to L transition after Z to H transition takes several us.

Could you please let me know why it takes longer?

From the datasheet, it is specified that tPZL is longer than tPZH.

I think this specification is related to this behavior.

Regards,

Itoh

  • 0
    TI__Mastermind 22920 points

    Hello Itoh-san,

    Thank you for your question. After output is enabled output first goes to the default state for max 30ns. After this it takes about 8.5μs max for output to start following input.

    Kazuki Itoh said:
    My customer found that the Z to H takes several tens of ns,

    What the customer is seeing here is the default state and not the input state.

    Kazuki Itoh said:
    but the H to L transition after Z to H transition takes several us.

    Here the device is still waiting for 8.5μs and then starts following the input. That is why the transition only appears to take 8.5 us.

    Yes, tPZL and tPZH are the specifications related to this behavior.

    Regards,
    Darrah