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Original question:

TMP708: How to Test the TMP708 functionallity at 20C - with Rset set to 100C trip point?

TMP708: SET Voltage Trip Threshold

Antonio Fadhel
Genius 9410 points
Part Number: TMP708

Hi Team,

My customer is planning to test the TMP708 in production by driving the SET pin with an external voltage. Can you please share the trip threshold voltage for the SET pin? Reading through the datasheet, the references seem to be temperature-dependent so a rough value at 25C would be helpful. Also, would a series resistor with the external voltage be needed, or can it be driven directly?

Thanks,

Antonio

  • 0
    TI__Mastermind 35895 points

    Hi Antonio,

    While it is technically possible to trip the output this way, I'm not sure that I can recommend doing it. I can't find any mention of this feature in the datasheet. 

    The datasheet has the formula for Rset vs Temperature, and this is also shown in Figure 2. The other thing you would need to know is the Rset current to convert this resistance to a voltage. This current isn't documented in the datasheet, but I can tell you it is about 10uA. It will vary with temperature; this is an intended part of the device operation. Since 20C corresponds to about 80kohm set resistor, this will develop about 0.8V at the SET pin. This means you would need to supply more than 0.8V at the SET pin to force the device to trip at ambient.

    thanks,

    ren

  • 0 in reply to Ren Schackmann
    TI__Genius 9410 points

    Hi Ren,

    Thanks for the quick response. The suggestion for the external voltage is from the following post: . Assuming the current source is biased to VCC and SET is high-impedance, I would think that an external bias lower than VCC might not be an issue since it would just reduce the current from the internal source. Can you confirm if this is the case? They need to run this test since changing the temperature for testing will not be feasible.

    Thanks,

    Antonio

  • 0 in reply to Antonio Fadhel
    TI__Mastermind 35895 points

    Antonio,

    In table 6.5, we have specified voltage at the SET pin to be 0V min and (Vcc) max. This is the only thing I have to go by. If these constraints are met, it should be OK to bias the SET pin high or low with an external supply.

    thanks,

    ren