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TPSI3050: Two-wire mode up to 60V

Pablo S.M.
Prodigy 10 points
Part Number: TPSI3050
Other Parts Discussed in Thread: LM317HV

Tool/software:

I would like to run the TPSI3050 in two-wire mode by switching through an optocoupler a battery voltage to the Enable Pin.

The problem is that the maximum voltage allowed at the Enable Pin is 48V and the battery can reach 54V when fully charged.

As a solution I was thinking of inserting an in-line 9.1V Zener Diode (e.g. ON Semi BZV55-B9V1) before the Enable Pin. 

The Zener diode works at 5mA and the TPSI3050 is configured for 6.8mA Enable current.

The goal is to subtract some voltage and reach maximum ~45V at the Enable Pin when the battery voltage is 54V.

Do you have some experience using the TPSI3050 in two-wire mode in applications up to 60V?

Maybe you have a suggestion for a more "elegant" solution.

Thank you in advance!

  • 0
    TI__Intellectual 940 points

    Pablo,

    Thank you for reaching out to our team over E2E.

    While your solution works when the TPSI3050 is enabled, it will not work when the device is off. No current will be flowing through the Zener and result in no drop in voltage, killing the TPSI3050. I recommend using an LDO to drop the voltage; something like the LM317HV or LM2936HV would fit well here.  

    Please reach out to me if you have any further questions. I am always happy to help!

    Regards,

    Jack Hemmersmeier

  • 0 in reply to Jack Hemmersmeier
    Prodigy 10 points

    Hello Jack,

    Thank you for your answer and the new ideas!

    I just have one remark abut the original proposal:

    When the device is off in two-wire mode (e.g. disconnecting the voltage by means of an optocoupler) it means that there is no voltage at the Enable pin to kill the TPSI3050, right?

    So when the TPSI3050 is enabled there is a voltage drop due to the current flowing through the Zener, and when the TPSI3050 is disabled there is just no voltage at the pin.

    Regards,

    Pablo

  • +1 in reply to Pablo S.M.
    TI__Intellectual 940 points

    Pablo,

    The series Zener diode will work in steady state, but I worry about any transient conditions where the TPSI3050 may see too much voltage. I would also recommend a higher voltage Zener implement this solution, perhaps a 1N4750A (27V). 

    The LDO solution will be the most robust and will have a more predictable transient behavior.

    Regards,

    Jack Hemmersmeier