I'm using ADUM4146 to drive SiC modules. Can you pls provide a guide/ method to design the desat protection circuit? How to calculate the Blanking capacitor value?
The blanking capacitor Cblank is used to create an external filter delay, which provides additional blanking time.
The additional time contribution due to Cblank can be calculated as:
where Ibias = 500uA for ADuM4146 and Vth is the Desaturation detect comparator voltage.
The total reaction time to a fault is calculated as:
T = Internal blanking time + external filter delay + comparator delay.
To protect a SiC device using Desat style protection it is important to understand the maximum energy that the SiC device can tolerate during the fault condition and design the total reaction time accordingly.
Typically the time to safely clear a fault is < 2uSec for SiC devices.
Here some references for further information: