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TRS3232E-Q1: Driver Continuous Overvoltage Protection

Fabian Geiger
Prodigy 40 points
Part Number: TRS3232E-Q1


Tool/software:

Hello,

in the Datasheet for TRS3232-Q1, the Drivers have a maximum rating of +-13.2V.
We need to protect against continuous overvoltages of up to 16V.

Could we simply use a series resistor and some clamping diodes to limit the voltage to less than 13.2V?
Do the driver outputs have clamping diodes? If so, where is the overvoltage clamped to`?

Thank you!

  • 0
    TI__Genius 14712 points

    Hi Fabian,

    TRS3232E-Q1 does have ESD protection that clamps transients for short periods of time, but it does not protect against continuous overvoltage. You could use series resistors, but this would weaken the drive strength for the transceiver. 

    A better solution might be to use a Zener diode here. I will transfer this question over to our Protection Devices team as they can provide more information about best protecting the device. 

    -Ethan

  • 0
    TI__Mastermind 19990 points

    Hi Fabian,

    Right now we only have an 8.2V Zener and a 15 V Zener, so we don't have the right zener voltage for this application currently. 

    Regards,

    Sebastian 

  • 0 in reply to Sebastian Muriel
    Prodigy 40 points

    Hi Ethan and Sebastian,

    you said, that there are ESD Protection Diodes on the Driver. Where do they clamp to, when presented with a transient overvoltage?


    Using Zener-Diodes seems to be the simplest way to protect the driver. 8.2V Zeners might just be fine, as the driver typically outputs +-5.4V Signals.
    We would need some small resistance to limit the current though the Diodes when shorted to battery, so a small loss in drive strength is not avoidable.


    Regards,
    Fabian

  • +1 in reply to Fabian Geiger
    Guru 318050 points

    The ESD protection triggers at voltages above ±13.2 V, and cannot handle continuous overvoltage. It is not specified whether it clamps to ground, VCC, or V+/V−.

    Please note that an RS-232 driver is designed to drive an RS-232 input, which has a resistance of 5 kΩ ± 2 kΩ to ground. The series resistor must be much smaller than that.

  • 0 in reply to Clemens Ladisch
    Prodigy 40 points

    Hello Clemens,

    Thank you for the additional Information. If the ESD Protection is inactive for voltages below ±13.2V, then it should not matter, where it clamps to. 
    The external protection will have to ensure, that there are no larger voltages and clamp accordingly.

    The series resistor would be in the region of 200-500Ω. Given that the minimum output resistance of the driver is 300Ω, that would reduce the output levels by ~600mV. This should be manageable for our application.

    Thank you!
    Regards,
    Fabian