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MAX3232: TVS diode selection

Austin Do
Expert 3275 points
Part Number: MAX3232
Other Parts Discussed in Thread: ESDS452

Tool/software:

Hello team,

Based on the below article, SMBJ8.0CA is recommended for MAX3232. I don't understand this because abs rating is lower than Vrms. Can you explain why this part is recommended?

https://www.ti.com/lit/ta/sszt891/sszt891.pdf 

Best,

Austin

  • 0
    TI__Guru 72711 points

    Austin,

    I'm not completely sure why that one was chosen it ultimately depends on the max peak current you're expecting. If the peak current is lower than 44.2A then the device will clamp earlier.

    TI also has its own protection devices, you may want to take a look at those instead. I can reassign this thread to someone in that team to provide a better substitute.

    -Bobby

  • 0 in reply to BOBBY
    TI__Expert 3275 points

    Hi Bobby,

    Thanks for reply. Looking forward to getting answer from others.

    So, if the customer chooses TVS diode, diode spec should have

    Vrwm > 5.2V(output of MAX3232)

    Vc < 13.2 (Abs rating of output pin)

    Is this correct? 

    Best Regards,

    Austin

  • 0 in reply to Austin Do
    TI__Guru 72711 points
    Austin Do said:
    Vrwm > 5.2V(output of MAX3232)

    I think the working voltage should be larger than 6.5V since out device typical is probably closer to +/-5.5V

    And yes the max clamp voltage should target less than +/-13.2V. They will need to use a bi-directional TVS. 

    I'm re-assigning this thread now. 

  • 0
    TI__Expert 8120 points

    Hi Austin, 

    Yes, we recommend the clamping voltage of the diode to be at or less than the abs max of the IC needing protection. Since clamping voltage is a transient voltage and the transceiver abs max is a DC voltage, there is some wiggle room, but testing would be required to know for sure. 

    In this case, I don't see a huge problem with using the SMBJ8CA but if you would prefer a smaller device then I can recommend our ESDS452 device.

    Best,

    McKenzie