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SN75LP1185: ESD Protection

Darren (FAE)
Expert 5483 points
Part Number: SN75LP1185
Other Parts Discussed in Thread: SN75C185, SN75185, , TRS3253E

Currently, I have a customer using back-to-back 20V zener diodes for ESD protection with SN75C185. They have this protection on Rax (input connected to the outside) and Dyx (output connected to the outside).

But they want to switch to SN75185 - because the DS shows this device has internal ESD protection on Rax and Dyx included in the device.

Can you confirm if the SN75C185 has any ESD protection on Rax and Dyx? (From page 3 of the DS, it looks like there is protection - can you confirm if this is back-to-back ESD protection with ~??V clamp capability? (Like 20V) kV-rating?

Can you confirm if the SN75185 ESD protection on Rax and Dyx is back-to-back ESD protection with ~??V clamp capability? kV-rating?

Can you confirm if the SN75LP1185 has back-to-back ESD protection on the receiver inputs and driver outputs (Rax and Dyx)? If so, what is the clamp voltage? kV-rating?

This will be a huge help - thanks.

Darren C 

  • 0
    TI__Guru 50795 points

    Hi Darren,

    HBM ESD ratings for bus pins are available on the product details section of each devices' page on ti.com:
    SN75C185: 2kV
    SN75185: 10kV
    SN75LP1185: 15kV

    Both SN75185 and SN75LP1185 list their ESD ratings in the Absolute Maximum sections of their datasheets. This will provide the kV rating for each pin (bus and logic) and test model (HBM and MM). The clamp voltage for internal ESD protection will be at or near the absolute maximum value specified for that pin - once this value is exceeded, the circuit will try to clamp the voltage. Note that these circuits are not capable of dissipating as much energy as external protection components.

    Let me know if this information is what you were looking for.

    Regards,
    Eric Schott

  • 0 in reply to Eric Schott1
    TI__Expert 5483 points

    Hi Eric,

    That information was exactly what I was looking for - thanks!
    It is my understanding the ESD structures for these three devices will not be sufficient for the higher-energy dissipation needed for IEC 61000-4-x testing - correct?

  • 0 in reply to Darren (FAE)
    TI__Guru 50795 points

    Hi Darren,

    That's correct, these older devices were not tested under the IEC61000-4-2 standard. If you're looking for an integrated solution, newer devices such as TRS3253E are often rated under this standard. Let me know if you're looking for something specific that you can't find in the RS-232 products folder on ti.com.

    Regards,
    Eric Schott