russ
Junior Member level 1
Hi
I need to know how to calculate the component values (RC) for the count pin on UCC35702. I have read the datasheet and understand the count pin is being used to count the number of current pulses before it triggers and shuts the IC off. The count pin needs to be four times the VSclamp resistor times (1-Dmax). Currently, I am using a 100k resistor for Vsclamp. As per the datasheet, my calculation is 100k*4*(1-0.5) is 200k. I am using a 232k resistor in parallel with a 0.1uF capacitor on the count pin and the other side is grounded. I am not sure how to calculate the number of counts the loop would go through before it trips.
Currently, I am using it in a application where it seems to destroy the current sense resistor with the FET. The current sense resistor is 0.05ohm able to tolerate 4A and the FET is rated for 14A. So there is enough margin for the IC to react and shutdown before it takes the CS resistor with the FET. I am guessing it is not working properly because my chosen component for count pin is not right.
Anyone who has used this IC or understands the working of this IC, your help would be really appreciative. Datasheet Attached
Thanks in advance
I need to know how to calculate the component values (RC) for the count pin on UCC35702. I have read the datasheet and understand the count pin is being used to count the number of current pulses before it triggers and shuts the IC off. The count pin needs to be four times the VSclamp resistor times (1-Dmax). Currently, I am using a 100k resistor for Vsclamp. As per the datasheet, my calculation is 100k*4*(1-0.5) is 200k. I am using a 232k resistor in parallel with a 0.1uF capacitor on the count pin and the other side is grounded. I am not sure how to calculate the number of counts the loop would go through before it trips.
Currently, I am using it in a application where it seems to destroy the current sense resistor with the FET. The current sense resistor is 0.05ohm able to tolerate 4A and the FET is rated for 14A. So there is enough margin for the IC to react and shutdown before it takes the CS resistor with the FET. I am guessing it is not working properly because my chosen component for count pin is not right.
Anyone who has used this IC or understands the working of this IC, your help would be really appreciative. Datasheet Attached
Thanks in advance