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ISO5452: Delay time Problem during OCP

Brian Wang0928
Genius 14030 points
Other Parts Discussed in Thread: ISO5452

art Number: ISO5452

There is Zener Diode and Diode on the circuit of the ISO5452 between DESAT and GND pin as recommanded below.

We know there are some parasitical capacitance inside the Zener and Diode. Can these affect the response time during over current protection with DESAT pin? What's your opinion with this? or how to deal with it?

Very thanks.

Regards,

Brian

  • 0
    TI__Guru**** 189401 points
    Hi Brian,

    Ni hao!

    Please see section 10.2.2.8 DESAT Diode and DESAT Threshold of the data sheet.

    You are correct, the capacitance of the diodes will add to the 220 pF cap. The sum of all that capacitance is then combined with the value of RS to make the blanking time to ignore false trips at turn-on. You can tune the RC time constant of RS in combination with the capacitance to get the blanking time required in your system.

    Let us know if you have further questions.
  • 0
    TI__Expert 4875 points
    Hi Brian,

    Don is right that the DESAT Diode, DDST, in series with RS will affect the timing of your circuit as described in the datasheet. However, the parasitic capacitance of the Zener diode will not have an effect, as the current will take the path to the blanking capacitor, 220pF, to charge it. The effect of the Zener diode/parallel diode capacitance will not affect the DESAT timing.

    Regards,
    Audrey