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CSD17382F4: Back to Back ESD protection

Christelle Saliba
Prodigy 40 points
Part Number: CSD17382F4
Other Parts Discussed in Thread: CSD13381F4,

Hello, 

I have designed a circuit in which I have used the CSD13381F4. I realized through testing that once a voltage is present on the source, there automatically is a voltage on the gate and this made me realize that there is a diode from source to gate which will conduct when forward biased. I researched about this single ended ESD protection diode and I found more information here: https://e2e.ti.com/blogs_/b/powerhouse/posts/what-type-of-esd-protection-does-your-mosfet-include. I am interested in removing the issue of having a voltage on the gate due to a diode which allows a voltage present on the source to be present on the gate and thus I think that a back to back ESD protection is suitable for my case. 

Can you please confirm? Also, I did not quite understand how the 2 diodes would work and allow correct working of the MOSFET. I chose the CSD17382F4 as it is of same footprint to the one i am actually using however I am confused on how do these diodes work and still provide correct functionality of the MOSFET.

I would highly appreciate your clarification.

Thank you.

Best regards,

Christelle Saliba

  • 0
    TI__Mastermind 33065 points

    Hello Christelle,

    Thanks for your interest in TI FETs. The CSD17382F4 gate ESD structure can be thought of as two series diodes with common cathodes with an anode connected to gate and an anode connected to source. No matter the voltage polarity between gate and source, one diode is always reverse-biased and blocks current flow. During an ESD event, the structure behaves as back-to-back zener diodes clamping the gate-source voltage to protect the gate oxide. As you have discovered, the single-ended gate ESD diode will conduct if the source voltage is higher than the gate voltage. The CSD17382F4 should work in place of the CSD13381F4 and prevent this issue yofrom happening. However, keep in mind that the leakage of the b2b structure is much higher; μA instead of nA.

    Best Regards,

    John Wallace

    TI FET Applications

  • 0 in reply to John Wallace1
    Prodigy 40 points

    Hello John,

    Thank you for the reply! I am still concerned about the diode whose anode is at the gate. Would it affect the VGS on the MOSFET or do I treat the FET as if it is single ended when supplying the gate. I am interested in the Ids and I am afraid the second diode would add problems.

    Best,

    Christelle

  • +1 in reply to Christelle Saliba
    TI__Mastermind 33065 points

    Hello Christelle,

    The b2b ESD protection will not effect VGS of the MOSFET. You can drive this FET as you would drive a device with no ESD protection. As I pointed out in my previous response, this is a higher leakage structure which is specified in the datasheet (IGSS & IDSS). Unlike the single-ended ESD diode, a negative VGS will not cause a problem as long as the voltage is less than the abs max specified in the datasheet.

    Best Regards,

    John

  • 0 in reply to John Wallace1
    Prodigy 40 points

    Well Noted. Thank you!