Our Ask An Expert knowledge base contains answers to questions from designers like you. Browse the knowledge base by category or search key words. Not seeing what you need? Ask An Expert a question of your own.
Subject: Calculating Rt and Ct in fig. 12 of AND8253/D App Note by Lepkowski. Hi, I need to provide surge suppression for a CAN transceiver in a system that will be subjected to Power Short-Circuit tests. In these tests all external I/O are shorted to a 32V source for a one minute duration. An unprotected NUP2105L would breakdown, conduct and burnout during this test. Fig. 12 of AND8253/D App Note by Lepkowski shows a way to avoid this problem. My question is: how do I calculate the values of Rt and Ct? Should Rt be a "pulse withstanding" type? How much power can I let the NUP2105L dissipate safely? 250mW at 25deg C? What would be a good value for Ct? Is there anything special about Ct? Thank You.
The Rt in the figure should be selected to ensure that maximum current rating of the clamping device is not exceeded. The magnitude of the capacitor is not critical and a value of 0.1 uF should be OK.
Please refer to our fig.12.
However, for this purpose to survive 32V short we have also designed in a new part, NUP3105 which is expected to be released to market by October 2014.
Answered by: ON Semiconductor
2014-06-05 09:17:18.661