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ISO7710: Start up time / power up with 60 Hz

franziskus
Expert 6706 points
Part Number: ISO7710

Team,

what's the maximum start-up time for ISO7710?
Is it possible to power the device with AC voltage 60Hz and still get the signal across the isolation barrier?

Thanks

  • 0
    TI__Mastermind 49445 points
    Hi,

    The worst case start-up time for ISO7710 is 180µs, a typical value could be much lower than this.

    I am not sure if I understood your question on AC voltage very well, could you elaborate on this>? Recommended operating voltage for ISO7710 is 2.25V to 5.5V whereas absolute maximum voltage is -0.5V to 6V, which states that you can only apply a positive voltage between 2.2V to 5.5V for the device to operate normal. Thanks.


    Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    TI__Expert 6706 points
    Hi Koteshwar,

    the idea is to replace an opto-coupler with the ISO7710. The signal to be isolated is a simple on/off signal for a switch.
    The AC source is rectified and the customer will take care of the Vcc specs of the part, but it will not be a DC voltage source. DC source is an option if AC source does not work.

    The basic question is, will the signal be able to cross the isolation barrier when Vcc is switched on/off with 60Hz?
    From the worst case start-up time I would guess that it is possible, but do you have experience with such use cases?

    Thanks and best regards
  • 0 in reply to franziskus
    TI__Mastermind 49445 points
    Hi,

    Thanks for sharing more details about customer's application. You did mention that the AC source is rectified, do you know if it is filtered as well? Or is it unfiltered pulsating DC that goes from 0V to peak voltage (<5.5V) then to 0V and repeats?

    In case of latter, the device will turn-off every time supply goes below UVLO and turns-on when supply goes above UVLO. Like you mentioned, 180µs of start-up time isn't much and data will be transmitted across isolation barrier.

    One thing to keep in mind is that, input signal (INx) should always be less than supply voltage i.e., INx < [VCCx+0.5V]. This means that as supply voltage goes down, input signal voltage should also go down so not to violate device specifications. If this is taken care, then device should work fine. Thanks.


    Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    TI__Expert 6706 points
    That's very useful Koteshwar, thanks for your help.

    Do you see any issue with constantly switching on/off the device (degradation or such)?

    Thanks
  • 0 in reply to franziskus
    TI__Mastermind 49445 points
    FRAMziskus,

    ISO7710 turning ON / OFF at a rate of 60Hz shouldn't be any issue and there shouldn't be any degradation in device performance or lifetime.


    Regards,
    Koteshwar Rao