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ISO7731-Q1: Output State in transition from PU to PD at Vcco

Hiroshi Katsunaga
Mastermind 6480 points
Part Number: ISO7731-Q1

Hello,

My customer have some question about output state in transition from PU to PD at vcco for ISO77xx family.

[Background]

I show their block diagram and the timing chart that they are concerned as follows.

<Use Case>

Vcci in ISO77xx is the same power rail as MCU.

Vcco in ISO77xx is the different power rail as LIN Transceiver.

Vcci = PU

ENx = Open

INx = High

Vcco = PU -> PD -> PU

In this case, they want to keep high on the OUTx.

<My understanding>

Zone 1 : OUTx = High (However, the OUTx high level depend on Vcco voltage.)

Zone 2 : ??? (I think it is not made Low state and High-Z state.)

Zone 3 : OUTx = High (However, the OUTx high level depend on Vcco voltage.)

[Q1]

Is "Undetermined" listed in D/S (SLLSEU3A) P.20 Table 2 the meaning as "Undefined" ? 

[Q2]

In what kind of state will the OUTx be in Zone 2 ?

[Q3]

Is there a way to maintain the OUTx in the state of High in Zone 2 ?

(I accept that it depend on Vcco voltage.)

Best Regards,

Hiroshi Katsunaga

  • 0
    TI__Mastermind 49495 points
    Hi Hiroshi-san,

    Thank you for posting all the necessary details regarding your query, please find below my response to your questions.

    [A1]
    Yes, when VCCO is PD the output is in "Undetermined" / "Undefined" state.

    [A2]
    In Zone 2, VCCO is going to be less than 1.7V. For VCCO<1.7V, the output will be in high impedance. Please note that the parasitic capacitance on output pin may take a small amount of time to discharge fully based on the load connected.

    [A3]
    Like you have mentioned, without VCCO or any other power supply available at output it would not be possible to hold the pin HIGH.


    Thanks & Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    Mastermind 6480 points
    Hi Koteshwar-san,

    Thank you for your fast response and your clear comments.

    I understood your all comments.

    Thank you for your cooperation !

    Best Regards,
    Hiroshi Katsunaga