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ISO7242, ISO7842 - propagation delay

Ryuji
Guru 20090 points
Other Parts Discussed in Thread: ISO7842

Hello,

Is the propagation delay of ISO7242 and ISO7842 varied at each Input pulse ?
Or the propagation delay is not varied at each input pulse ?

Best Regards,
Ryuji Asaka

  • 0
    TI__Guru 55795 points
    Hello Ryuji,

    For a given operating condition, propagation delay of ISO7242 & ISO7842 for each input pulse should almost remain the same. The primary factors that can vary propagation delay are VCC and temperature variations.

    Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    Guru 20090 points
    Hello Rao san,

    The customer measured the tpd as about 150ps on the EVM.
    Is this tpd same on the same Vcc/Temperature ?

    The input signal is one-shot pulse(duty=5~10%).
    The frequency is almost fixed. It is not changed dynamically.

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryuji
    TI__Guru 55795 points
    Hello Asaka-san,

    Which device did customer measure for tpd? For VCC1 & VCC2 = 5V, tpd for ISO7242 should be between 18ns to 42ns and for ISO7842 it should be between 6ns to 16ns. These values are obtained on circuit with input frequency of 50kHz with 50% duty cycle. The variation in these values is due to the variation in temperature. If VCC is changed the above range will change wide range as given in the datasheet.

    Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    Guru 20090 points
    Hello Rao san,

    Sorry. I mistake to write.
    The 150ps is not tpd. Device is the ISO7242.
    The 150ps is the difference between each tpd on input pulses. ("tpdx" - "tpdx-1").
    From your reply. I understood that the 150ps is not varied on the same Vcc. Temperature condition.
    Is my understanding correct?

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryuji
    TI__Guru 55795 points
    Hello Asaka-san,

    Your understanding is correct, for the same VCC and Temperautre we do not expect for a channel to have varying propagation delay.
    We do see channel to channel variation in tpd for the same VCC and across Temperature which is speced in datasheet as not to exceed 2ns for ISO724xC and 1ns for ISO724xM under worst case conditions though typically it would be 0ns.

    Regards,
    Koteshwar Rao