ADUM4221 DT pin connect to 5V(VDDI)

Hello

           Customer use SI8233 on board. We will use ADUM4221 to replace it. Customer don't use DT function of SI8233 and DT pin connect to 5V(VDDI).

           Could ADUM4221/ADUM4221-1 DT pin connect to pull hign (5V) for direct replacement? Or ADUM4221-2 show NC pin but that datasheet show( No Connect. Do not connect to these pins). Does ADUM4221-2 also connect to  pull hign (5V) directly? Or we do not connect to any circuit on DT pin for ADUM4221-2. Thank you. 

BR

Patrick

Parents
  • +1
    •  Analog Employees 
    on Mar 17, 2021 3:51 PM

    Hello Patrick,

    The ADuM4221-2 is the best option here. Pin 6 and 7 are actually not internally connected, so you can pull them to 5V without a problem. The ADuM4221-2 does not have built in deadtime, so deadtime must come from the controller, and the controller must make sure shoot-through does not occur at the power stage.

    The ADuM4221 and ADuM4221-1 cannot have the DT pin pulled up to 5 V. For the ADuM4221 and ADuM4221-1, there can only be a resistor to GND1 placed on the DT pin (pin 6), no voltage source can be applied to pin 6.

    RSchnell

  • Hello RSchnell

                     Customer needs overlap and do not use DT function. ADUM4221-2 looks not suitable due to no overlap function. ADUM4221 looks good. But how to disable DT Pin of ADUM4221 for customer? Thank you. 

    BR

    Patrick

  • +1
    •  Analog Employees 
    on May 7, 2021 6:00 AM in reply to patrickchen@morrihan.com

    Hello Patrick,

    If the customer needs a part that allows overlap between the outputs, using the ADuM4221-2 will work. There is no DT pin on the ADuM4221-2.

    If the customer is looking to have the minimal deadtime allowed, Please use the ADuM4221 and set the resistor on the DT pin to 10 kΩ. This will result in a minimum deadtime of around 62 ns. The DT pin cannot be left unconnected, and must have a resistor to GND1 on it.

    RSchnell

  • Hello

               ADUM4221-2 looks no overlap function, right ? Thank you. 

            

    BR

    Patrick

  • +1
    •  Analog Employees 
    on May 9, 2021 6:20 PM in reply to patrickchen@morrihan.com

    Hello Patrick,

    It is correct that the ADuM4221-2 does not contain overlap protection. The ADuM4221-2 will allow both channels to be on at the same time if the inputs are both high.

    Overlap protection and deadtime control are very related. In an ideal overlap protection only scheme, the deadtime would essentially be 0 s. Deadtime control also does not allow overlap between the outputs, but spaces the timing between the outputs by a minimum timing.

    What does "disable the DT pin" mean? The lowest deadtime we can achieve  with the ADuM4221 is with a 10 kΩ resistor, resulting in around 62 ns. The ADuM4221 provides both deadtime control and overlap protection. If the customer needs low deadtime, but also overlap protection, this is the configuration they should use.

    If the customer is looking for less than 62 ns deadtime, using the ADuM4221-2 with complementary inputs on the VIA and VIB pins with proper deadtime between them can achieve this. The ADuM4221-2 does not have overlap protection, so if there is an input signal where both VIA and VIB are high, both outputs VOA and VOB will go high. This is not the exact same action as the SI8233 with the DT pin held to VDD1.

    1) Is there deadtime provided by the controller square waves?

         If no deadtime is being provided, or the deadtime is not guaranteed to be trusted, I would recommend the ADuM4221.

    2) Does the customer need overlap protection?

         The ADuM4221 is the best fit, but will come with a minimum deadtime.

    3) What deadtime is needed in the system?

         If a deadtime over 62 ns is needed, setting the DT pin on the ADuM4221 to 10 kΩ is the best solution.

    RSchnell

  • Hello RSchnell

            Customer use SI8233 and DT pin pull high and looks default dead time 400ps. So we can use ADUM4221 that put 10K resistor to GND for 62ns lowest dead time. Correct? Thanks.

    BR

    Patrick

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