• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 30 subscribers
  • Views 543 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

TMP451: Could we use NPN with TMP451?

TMP451: Understanding TMP451

Bharath Krishna
Prodigy 110 points
Part Number: TMP451

Hi ,

I'm using TMP451 in my desiign to monitor remote temperature.Just wanted to understand how connecting a transistor to D+ and D- pins will help in determining the temperature.

Thanks

  • 0
    TI__Expert 6820 points

    Hi Bharath,

    Please see our "The Engineer's Guide to Temperature Sensing" for the fundamentals information on temperature sensing.  Chapter 1:Introduction "IC sensors" section and Chapter 2: Section 2.2 "High-performance processor die temperature monitoring" should give a good basic understanding of how remote temperature sensors work.  Here is the link:http://www.ti.com/lit/ml/slyy161/slyy161.pdf.  

    In short, the remote temperature sensor applies different currents to the transistor and measures the change of Vbe voltage.   Using the equation of the temperature dependence of the band gap of silicon, the temperature of the remote transistor can be calculated. 

    Thanks,

  • 0 in reply to David Vaseliou
    Prodigy 110 points

    Hi,

    Thanks for the information.

    As per my understanding,when the temperature of the remote location where the  transistor is placed increases the Base-emitter voltage drop increases which is sensed by D+ and D- pins.Is the correct?

    Also,i wanted to know what value determines the maximum temperature that can be sensed by a BJT?

    Thanks in advance. 

  • 0 in reply to Bharath Krishna
    TI__Expert 6820 points

    Hi Bharath,

    To be more specific, when the temperature of the transistor increases the change of the Base-Emitter voltage will increase which is sensed by the D+ and D- pins. 

    The equation that is used to calculate the temperature of a BJT is taken from the expected behavior of common semiconductor BJTs.  If a BJT drifts off from this expected behavior, the equation will no long hold true and the temperature would be hard to determine.  The TMP451 also has spec limits that need to be followed and can be found in the electrical characteristics table in the datasheet.  

    Thanks,