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CD74HC4067: EFT or surge protection

Part Number: CD74HC4067
Other Parts Discussed in Thread: TPD2E2U06, TVS0500

Hi all, 

I see that the device has internal diode clamps for protection. But what is the purpose of diode clamp , is it for continuous over voltage or transients like surge or EFT. If we suppose diode clamps are for continuous overvoltage protection on the pin, then what is the surge or EFT capacity of the pins. Can i use an external TVS diode with clamp level of 14V for surge protection

  • Hi Naveen,

    This device does not support integrated Surge or EFT protection feature. There might be some minimal internal diode protection for basic CDM (Contact discharge) and that' why the clamping current has been specified.

    In general, most of our Analog switches the required level of ESD HBM (Human-body model) and ESD CDM (Contact device model). All new devices released to market at minimum support +/-250V CDM and +/-1000 HBM and the actual supported levels are specified in datasheet. These protect against over voltage/ over current events as specified by both the models.

    If the application needs to be protected against higher than specified ESD and/or Surge requirements, an external surge protection diode can be used and is a common practice. Please take into account the working voltage required while selecting the diode and any parasitic capacitance/leakage that is added from the diode itself into design budget. 

    Hope this helped.

    Thank you,

    Regards,
    Sandesh

  • Hi Sandesh,

    Can you suggest on the clamp level on the pin for a 5V multiplexer or can i use 14V TVS diode on the pins

  • Hi Naveen,

    Let me check with my Diodes team and get back to you on the recommendation. The CD74HC4067 for a 5V supply rail, can allow upto 5.5V (VCC+0.5V) on the I/O (Signal) pins. For a successful signal transfer, the Diode VRWM voltage should be higher than this so that there is no interference with operation across temperature.

    Could you help me understand the use case. How are you planning to use the Mux itself, type of signals, bandwidth etc. I would also like to understand what is the source of transient event and what type of protection is needed. 

    We do have TVS flat clamp surge diodes as well as basic ESD protection with some level of surge protection and there are multiple options based on the potential fault event. See below.

    https://www.ti.com/interface/circuit-protection/esd-protection-and-tvs-surge-diodes/overview.html

    Thank you,

    Regards,
    Sandesh

  • Hi Sandesh,

    We are using it for sensing temperatures using NTC. We want to ensure basic surge protection for 8/20usec waveform. So request you to confirm on the clamp voltage level

  • Hi Naveen,

    You can use TVS0500 (flat clamp TVS diode) or TPD2E2U06 (uni-directional ESD diode). Both these devices support surge protection and allow 5V signals.

    Thank you,


    Regards,
    Sandesh