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ISO7140FCC / voltage on the undetermined

Guru 20090 points
Other Parts Discussed in Thread: DAC1220, ISO7140FCC

Hello,

The customer use ISO7140FCC to digital input(SCLK etc.) of DAC1220.
The DAC1220 dital input pins absolute maximum rating is "–0.3 to DVDD + 0.3"
If we use ISO7140FCC with VCCI=3V and VCCO=0V, the output is Undetermined state.

In this case, are there any possibility of violation for DAC1220 digital input pin?

 Best Regards,
Ryuji Asaka 

  • Hello,

    I'm looking forward to the reply.
    The power on sequence between VCCI to VCCO/DCDD is 1ms or 10ms or 100ms.

    Best Regards,
    Ryuji Asaka
  • It depends on the specific application environment.
    If ISO7140FCC VCCO is at 0V, the output will be very close to 0 V, but stray coupling to switching nodes could take it higher.
    However, the voltage will not exceed VCCO + one diode voltage (0.3 V to 0.8V), due to ESD and other diodes.
    You may have to try the device in actual application and monitor results.
  • Hello Saleem san,

    I have additional questions for this post.

    (1) OUT votlage
    INx, ENx,Outx Absolute maximum ratings of ISO7140FCC  is -0.5V to VCC+0.5V.
    However, you said that the OUTx voltage will be "0.3 V to 0.8V"  when VCC2=0V.
    Is this "0.8V" correct ?
    If this is correct the device will be damaged when VCC2=0V.


    (2) Absolute Maximumr Ratings
    The INx,ENx,OUTx absolute maximum ratings is -0.5V to VCC+0.5V.
    I think that the OUT voltage rating is VCC2+0.5V and IN voltage rating is VCC1+0.5V.
    Is my understanding correct ?

    (3) Current Ratings of ESD and other diodes
    Could you please let me know the current ratings of ESD and Other diodes which you can share with us ?

    Best Regards,
    Ryuji Asaka

  • Hello Saleem san,

    Sorry for bothering you.
    I'm looking forward to your reply.

    Best Regards,
    Ryuji Asaka
  • Asaka-san,

    My responses are below:
    (1) As I said earlier, when VCC2 is powered down, then the output is likely to be very close to 0V. The stray coupling can move this voltage within a diode drop (0.3V to 0.8V). In this case, the device won't get damaged.

    (2) Yes, your understanding is correct.

    (3) This device passed 4000 V HBM ESD level. Is this what you are asking?
  • Hello Saleem san,

    Thank you for the reply.
    Regarding (3), I think that the device was broken by the current through due to ESD.
    And I would like to know the current rating of ESD diode, if there is.

    Best Regards,
    Ryuji Asaka