I'm not able to understand how to use Vi+ and Vi- pins of the driver.

GaN Systems has a half bridge eval board based on ADUM4121A. They have following connections- 

Is it necessary to provide a complementary input to each driver? Can I just provide Vi+ signal and leave Vi- floating? i.e connect HS_PWM-> Vi+(HS Driver) , LS_PWM->Vi+(LS Driver)  and leave Vi- of both drivers NC

added tags
[edited by: pranit at 6:16 AM (GMT -5) on 11 Dec 2020]
  • +1
    •  Analog Employees 
    on Dec 22, 2020 6:58 PM 2 months ago


    The VI+ and VI- pins on the ADuM4121 allow you to drive the inputs a few different ways.

    1) The first, and most intuitive is to drive each ADuM4121 with positive logic. To do this, connect each VI- to GND1. Then, with two different PWM signals, drive the two separate VI+ pins with complementary signals. This is the closest to what you described. You do need to ground the VI- pins though, and not leave them floating.

    In this mode, you could even use both VI- pins as disable pins (raise VI- pins to disable the outputs).

    2) The second method is to provide both VI+ and VI- pins with complementary logic. By having the VI+ of the lowside driver driven with the same signal as the VI- as the highside (and vice versa) you get one more layer of protection from shoot through. If the controller outputs high on both the HS_PWM and LS_PWM as the same time, a shoot through event won't occur on the outputs, as both outputs will go low. It is not necessary to operate the ADuM4121 in this mode, but it also doesn't hurt.


  • Such a succinct and concise answer! Thanks RSchnell!