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Original question:

TMP422: n factor correction of BJT in an IC

TMP422: Use TMP422 to measure series tempeture diodes

Jeff Xie
Intellectual 1780 points
Part Number: TMP422
Other Parts Discussed in Thread: REF200, ADS1120

Hello,

My customer wants to use TMP422 to measure temperature of series diodes. As figure 1 shows. Is TMP422 able to measure it? If so, what is the address of TMP422?

  • 0
    TI__Guru**** 244400 points
    Hello Jeff,

    The TMP422 is designed to sense remote temperature across a single diode. The above system may not have been tested. I will need to check. Also is the 100 uA current source shown an external current source, since the TMP422 drives the current, so any external current source may interfere with the correct readings.
  • 0
    TI__Guru**** 244400 points
    Hello Jeff,

    In my discussion with my colleague, it seems we cannot use the TMP422 to measure via 2 diodes. Let us see if there is some other configuration (which may require extra components), that can be used for sensing.
  • 0 in reply to Amit Ashara
    TI__Intellectual 1780 points

    Hello Amit,

    Do we have sockets to measure via 2 diodes?

    If not, can we use a current source like REF200 and a two channal ADC or ADC with current source like ADS1120?

    The below figure is the detail of the temp diode.

  • 0 in reply to Jeff Xie
    TI__Guru**** 244400 points
    Hello Jeff,

    In theory yes, it should be possible. If you refer to the following Application Note on Remote Temp Sensor (pg 5-6)

    www.ti.com/.../sboa173.pdf

    You will see that the measurement of Vbe requires a number of parameters. By using 2 or more current sources to drive the diode current, you can remove some of the silicon parameters, simplifying the calculation. So instead of 1 current sources you would need 2 current sources.