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ISO5452: DESET PIN

Brian Wang0928
Genius 12520 points
Part Number: ISO5452

In the d/s, it says that the 100-Ohm to 1K-Ohm is recommended to connect in series with the DESAT diode. However, my customer already places ~6K-Ohm Rs in the mass production for DESAT threshold voltage when short circuit event is happened. So far it looks it has no big problem. 

Customer would like to know:

1. Is there any side effect with 6K Rs?

2. What's the purpose of the Rs? Does the Rs and 220pF form a LPF for good noise immunity?

3. What's the max. resistor value for Rs with ISO5452? Is there limitation for Rs?

 

  • 0
    TI__Expert 5020 points

    Hi Brian, 

    1. There should be no side effect with the 6kOhm resistor, besides the expected DESAT voltage drop (500uA*6kOhm = 3V) 

    2. Besides forming a LPF, Rs can also act to reduce excessive current generated by the diode's junction capacitance into/out of DESAT node. 

    3. If Rs is too large, the forward voltage drop across the resistor would be too large and DESAT would false trigger during normal operation. In fact, in our latest generation of device (UCC217xx), we recommend at least 1kOhm for the DESAT resistor. 

    Hope this helps! 

    Vivian