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REF3033: Maximum external voltage connected to "OUT"-Pin

Alexander Raisle
Prodigy 130 points

Part Number: REF3033

Hello all,

in my Design I use the REF3033 for Mikrocontroller ADC-Reference Voltage (VDDA33). There is a permanent minimum current of 3.3mA at "OUT"-Pin.

I also have an Analog Input Pin (Ana_IN1) at my µC. To protect the Ana_IN1, I connected a 7k68-Resistor in series. Also I connected a Diode from Ana_IN1 to the "OUT"-Pin of REF3033, so Overvoltage will not destroy my µC and current is limited. Normally there are about 2V at the Analog Input, but in case of a failure, there could be a higher voltage (12V and more) and so there will be more than 3,3V at the "OUT"-Pin of the REF3033.

Now my question is, what will happen with the REF3033 in case of a failure. What is the maximum external voltage/current at the "OUT"-Pin?

Thanks in advance

Best regards, Alex

  • 0
    TI__Mastermind 19570 points

    Hi Alexander,

    The ABS Max for the Vout pin is 5V. If you connect 12V under any circumstance, it will violate ABS max. The REF3033 damage means it cannot regulate properly or at its correct voltage.

    In case of failure are you looking to see if it will be open or short?

  • 0 in reply to Marcoo Z
    Prodigy 130 points

    Hi Marcoo,

    thank you for your reply.

    Vin of the REF3033 is always the same - it is constant 5V. In case of a failure, there will be about 12V or higher at the Vout-Pin which comes from another supply.

    So if I understand you correctly that means if I connect a separate supply higher than 5V to the Vout-Pin of REF3033 it could destroy the regulator?

    Best regards, Alexander

  • 0 in reply to Alexander Raisle
    TI__Mastermind 19570 points

    Hi Alexander,

    That is correct. The REF3033 can only source current and not sink. It will not be able to handle all the current from the 12V rail line and it will damage the device. If you need protection for 12V, since this is a 3.3V device, I would add a some sort of overvoltage protection or clamp device like a diode.

  • 0 in reply to Marcoo Z
    Prodigy 130 points

    Hi Marcoo,

    thanks again for your help - issue resolved.

    Best regards, Alexander