Hello ,

  I want to use ADuM4122 to switch loads or make shorts to GND or battery -- steady state not constant frequency--, but my question is if it can handle DC input at pin3;   

I have simulated and it seems it works, so what is behind the ADuM to be able to handle DC input - as it seems it uses "transformers" inside and it suppose to handle only AC inputs -- i.e  square control signals  of certain frequency 


  • +1
    •  Analog Employees 
    on Jan 21, 2020 6:35 PM


    The ADuM4122 is capable of holding the output of Vout and Vout_SRC high or low indefinitely. The internal iCoupler transmission transfers the data across the barrier, and allows for DC operation. The outputs of the secondary side (Vout and Vout_SRC) are meant to drive capacitive loads, and constant current draw from the pins is not recommended. Right now in the sim, R2 would have VDD2 across it, which would lead to too much power dissipation within the IC. The connection on Vout is good, and is how the part was designed to be used.

    Right now, I don't understand the purpose of R2 in the sim. Was this just to check the pin voltage and current? In an actual application, I believe the ADuM4122 would overheat from the R2 connection. If only one output is desired, I recommend looking at the ADuM4120, which can provide the functionality of the sim shown on Vout.


  • Thank you  RSchnell,  

      My mistake R2 connection, the idea was to put R2 in series to gate´ see SR control.

       I see, ADuM4120 seem a better option.

    Thank you.

  • 0
    •  Analog Employees 
    on Jan 21, 2020 8:57 PM in reply to FGarcia255

    Glad to help.

    One thing that sometimes gets overlooked is that the power supply for VDD2 has to be floating. Sometimes people use DC/DC isolated supplies from Murata or Recom, but an extra supply is usually needed. If your switching frequency is low enough (and it sounds like it is), check out the ADuM5230. That gate driver includes an isolated power supply inside the part! This greatly simplifies the design. You can ignore the second channel on the part if needed.