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TMP442: TMP442 current and algo info

Fabio Restivo
Prodigy 30 points
Part Number: TMP442
Other Parts Discussed in Thread: TMP461EVM, TMP468EVM, TMP468

HI, in the datasheet it is no clear what the sequences of couples of current the TMP442 applied (6uA ,12uA and after 60uA, 120uA, OR 6uA,60uA and after 12uA, 120uA) to the remote sensor, and what the calculation steps used by internal algorithm of TMP442 to find the final temperature. Could you please clarify these points? Our integrated remote sensor has a linear NF region only round low currents, hence I don't know if the TMP442 can be used in our case.

Regards

  • 0
    TI__Mastermind 42895 points

    Hi Fabio,

    The sequence of currents and the internal algorithm are proprietary TI information that we won't release.

    thanks,

    ren

  • 0 in reply to Ren Schackmann
    Prodigy 30 points

    Let me change the question please. If I have a diode that has a Vbe > 0.95V with 120uA at cold (outside the criteria for best accuracy mentioned in the datasheet) but with 6uA the diode has Vbe>0.25V ad hot (inside the criteria suggested in the datasheet) and I'm interested only to temp measures at hot (100C - 125C), the accuracy remain the best at hot?

    Regards

  • +1 in reply to Fabio Restivo
    TI__Mastermind 42895 points

    If you have IV data across temperature for your junction, I'd be willing to try to model it. You could also order one of our EVMs, but there isn't one available for TMP442. TMP461EVM or TMP468EVM are available. If there is an issue, I would expect it to present itself with all remote sensors on the market. We do occasionally encounter embedded junctions which are not compatible due to capacitance or forward voltage being too high. Typically these junctions are only intended to be used with a resistor for their -2mV/C coefficient. This app note talks about the temperature coefficient, if you are not familiar: https://www.ti.com/lit/sboa277 Remote sensors improve accuracy by employing delta VBE in addition to VBE described there.

    ren

  • 0 in reply to Ren Schackmann
    Prodigy 30 points

    Hi, thanks for the answer. I try to better explain the issue. Our is an integrated thermal diode inside a microcontroller. The ICN (current collector normalized) is linear at 125C with Vbe < 0.6V, that means round 2uA of current. In this range we have extracted a NF (ideality factor) of 1.015. If the Vbe > 0.65V (that means current > 7uA) the previous NF change dramatically e cannot be used. This is the reason why initially I asked what are the sequences of currents the TMP442 or TMP468, apply on the thermal diode. If I insert a NF=1.015 in the register of TMP442, it should inject current of 2uA maximum to remain in the region where NF is constant. If TMP442 force 120uA I think it is not compatible with our diode. Do you agree ?

  • +1 in reply to Fabio Restivo
    TI__Mastermind 42895 points

    You can't prevent it from sourcing 120uA, and this is going to be the case across the remote sensor market. It sounds like it is not compatible.

    ren

  • 0 in reply to Ren Schackmann
    Prodigy 30 points

    thank for the answer. Do you have some integrated components to support the characterization of embedded bjt in high-end processor ?

  • +1 in reply to Fabio Restivo
    TI__Mastermind 42895 points

    You need precision, low-noise current sources as described in the app note I linked previously: https://www.ti.com/lit/sboa277 If you need an ASIC to provide the bias current and digitize the voltage, look into RTD and other sensor AFE solutions. I'm not sure if the range of the IDAC shown is appropriate for junctions, but this app note shows biasing/digitizing an RTD: https://www.ti.com/lit/sbaa329 These products fall outside my product line, so it would be best to start a new E2E to ask about them. This will get your questions directed to the appropriate team.

    thanks,

    ren