Watchdog of AD740x  series

Hello

Coudl you teach me about the output logic level when the VDD1 of AD740x is off ?

VDD1 supply rarely  off  at fault condition of power circuit in our customer's circuit.

Question1

AD7400 and AD7401 datasheet P.1 says  that these devices include watchdog.

So,  I think that AD7400 and AD7401  output high or low when VDD1 is off.

Is it correctt ?

Question2

Regarding to question1 , does AD7402 and AD7403 have the same function ? 

Question 3

Regarding to 1 , could you teach me about the period of watchdog ?

Regards,

Terumasa

  • 0
    •  Analog Employees 
    on Apr 25, 2017 7:05 PM

    Hi Terumasa,

       Apologies for the delay. Below is the response for your inquiry.

       1. The VDD1 supplies the isolated side which includes the Sigma Delta modulator and the encoder side. The output is not valid since no data will be on the encoder side.

      2. Yes. They are of the same family.

     3.  I'll get back to you on this. I need to check details.

    Regards,

    Jonathan

  • Hi Jonathan,

    Thank you for your advice.

    Please let me know your advice when you checked  question3.

    Regarding to 1,   what  is  internal watchdog do ?

    I thought  that this watchdog is the same as the function of  typically icoupler product.

    ( When VDD1 is off,   secondery side outpust  H or L  for  informing VDD off )

    Regards,

    Terumasa

  • 0
    •  Analog Employees 
    on May 3, 2017 4:14 AM

    Hi Terumasa,

       I just had it confirmed, the watchdog is normally found on standard digital isolators but not on the AD7401A. Regarding the next question, when VDD1 is off, this means something happen on the hot side, the cold side(secondary) will retain the last known state of its output.

    Regards,

    Jonathan