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ADG4612 isolation mode to normal mode conditon

Hello.

I have questions about ADG4612.

I experimented in the order of 1, 2.

1 VDD Power off and input signal to VS(5V TTL 10 MHz).

2 And then. VDD supplied 5V ,VSS was GND and VS continued input signal.

In 2 of the conditions, AD4612 was supposed to be in path mode. But it was isolation mode.

Why do it remains isolation mode?

By the way, TTL frequency reduced, it return to normal mode.

Why is that?

Did it get Fault Recovery Time?

Best regards.

  • Hi Osamu,

    I think this is related to the peak value of your Vs signal at higher frequencies.  For the ADG4612 the switch will turn off if Vs > VDD+VT. Can you check that your Vs is below this voltage?  Note, once you trigger the switch off then due to the speed of this signal (100nsec period) the part could stay off as the fault recovery time is slow in comparison, in the order of 1.2usec.

    A good experiment to do would be to raise the VDD level and see if it still stays off.

    Regards,

    Eric.

  • Hi Eric.

    Thank you for your reply.

    I watched Vs waveform. As expected, it was distorted and the peak has been reached the threshold voltage.The switch was on, it was not distorted. But off ,it was distorted.

    In datasheet P17 isolation mode, "The switch inputs are high impedance inputs with greater than 475 kΩimpedance to VDD ground and across the switch. "

    I think switch off condition likes high impedance termination. So that square wave is reflected and distorted.

    Thus for this and  the fault recovery time were remained isolation mode.

    Therefore using high speed square wave, I should set peak voltage to Vdd have enough margin.

    Regards.

  • Hi Osamu,

    Glad to hear you made some progress on this issue.  Best of Luck.

    Eric.