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ESD224: Connection Question

Steve Sampson
Prodigy 90 points
Part Number: ESD224
Other Parts Discussed in Thread: ESD204

Good morning, 

I have a question about the ESD224 diodes. On our device they are connected in such a way that the system and connector sides are tied together. I am wondering if this is appropriate and if the device will function normally (and be protected) when connected this way? 

I have attached an image for your review. We are having issues with something and I want to see if this could be part of the cause or not. 

Thanks,

Steve 

  • 0
    TI__Genius 13700 points

    Hi Steve,

    Welcome to E2E!

    The ESD224 should not be used in this way. For the ESD224 to function properly the connector should be connected to the connector pins of the device and the system to the system pins of the device. This allows the ESD transient to go directly into the ESD224 so the system doesn't get exposed to such transients. In the way that it is currently connected the ESD device may be taking some of the impact of the transient, but the system might be exposed to it as well. Nevertheless, the ESD224 was not designed to operate the way that it is currently connected in the schematic.

    An alternative device that could be used here would be the ESD204. The ESD204 does not have input and output pins. This device has 4 protection pins, 4 pins that are not internally connected to the device, and 2 ground pins. The protection pins of the ESD204 simply have to be placed in between the connector and the protected IC so that the ESD transients are steered towards the ESD204 to protect downstream circuitry. Both devices have the same package, but since the ESD204 does not have input and output pins it is not P2P compatible, but could work on your application depending on the layout. If the ESD device in the PCB is placed in such a way that the protected pins are in between the connector and downstream circuitry then it might work. Refer to the following application note for more details on layout: ESD Layout Guide

    Best regards,

    Andy Robles

  • 0 in reply to Andy Robles
    Prodigy 90 points

    Would connecting it this way cause "problems" or just yield a lower ESD protection than connected as per your documentation? 

  • 0 in reply to Steve Sampson
    TI__Genius 13700 points

    Hi Steve,

    I don't believe this would cause problems during normal operation of the system. This can be checked by depopulating the unit and checking the functionality of the system. As far as ESD there would either be no or low ESD protection from the device. Since this is not in the recommended configuration the device will not behave as described in the datasheet. I recommend either fixing the schematic and board layout or explore the possibility of the ESD204 as suggested in my previous response.

    Best regards,

    Andy Robles

  • 0 in reply to Andy Robles
    Prodigy 90 points

    Would any PCB changes need to be made to drop in the ESD204, or could I simply make a BOM change?

  • 0 in reply to Steve Sampson
    TI__Genius 10652 points

    Steve,

    Apologies for the delay in response. I am taking over from Andy.

    Very minor PCB changes would have to be made to use ESD204 instead of ESD224. They are not drop-in for each other.

    Please see the below layout diagram for ESD204 & ESD224. ESD204 cannot pass the signal through the IC, and you must route the signal underneath the IC, this is the only modification required. Please note That It is OK to connect the NC terminals to the corresponding IO pins on ESD204 as suggested in the d/s.


    If this answered your questions, could yo ulet me know by pressing the green button? Otherwise please let me know if you have additional questions.

    Best

    Dimitri