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Original question:

TPS3808: Supply Voltage Vs Sense Voltage

TPS3808: Sense input voltage greater than VDD

Lee Wakefield
Prodigy 70 points
Part Number: TPS3808


I would like to use the TPS3808G33 device to sense an input voltage wiith a fairly wide dynamic range.  I am considering using a Schottky diode and current limiting resistor to clamp Vsense relative to VDD, resulting in Vsense being Vf above VDD.  This will satisfy the absolute max input requirement in the datasheet.

However, the maximum recommended operating Vsense input voltage is VDD.  Is it a problem if Vsense exceeds VDD?

  • 0
    TI__Genius 9375 points

    Hi Lee,

    There shouldn't be an issue for Vsense to exceed Vdd. The only concern would be that RESET would only be pulled up and outputting the value of Vdd.

    Thanks,
    Abhinav.

  • 0 in reply to Abhinav.Sharma
    Prodigy 70 points

    Regarding Vsense to exceeding Vdd, I see that the Recommended Operating Conditions in the -Q1 automottive qualified part specified that Vsense should not exceed Vdd.  However, the standard part does not have this limitation in the Recommended Operating Conditions.  Does your response apply to the -Q1 part?

    Also, I do not understand the comment about RESETn.  The datasheet indicates the RESETn signal is open drain and may be connected to a pull-up greater than Vdd.  "A pullup resistor from 10 kΩ to 1 MΩ must be used on this pin and allows the reset pin to attain voltages higher than VDD."

  • 0 in reply to Lee Wakefield
    TI__Genius 9375 points

    Hi Lee,

    The operating conditions for the part do mention Vdd as the max for sense, as you mentioned. Theoretically there should not be a change between the devices, but I will reach out to an expert on our team to see if there is a difference that can cause this discrepancy. I will get you a response by next week.

    For the comment about the pullup voltage, I think I left out some language. I was assuming you would pullup to Vdd, thus limiting the output voltage to that level. If you are pulling up to another voltage, this is the case you mentioned.

    Thanks,
    Abhinav.