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LM35: how to design with LM35

[FAE] Andrew Wang
Genius 10685 points
Part Number: LM35
Other Parts Discussed in Thread: LM135, TMP235

Hi Team,

Customer wants to understand some detail of how to design with LM35, please kindly help, thanks.

The temperature range need is -40 ~ 90 C.

(1)  When we connect like below, The -Vs is directly impact the accuracy of output? 

 

2. When we connect like below, it's a differential output and it still follows the same 10mV/C relationship, correct?

3. Any special cares for the diode we choose?

 

 

4. Comparing with LM135 design for same temperature range -40 ~ 90 C. Can we follow circuit like above to make it differential output with single supply? Thanks.

Andrew 

  • 0
    TI__Expert 4875 points

    Hello Andrew,

    1) Vs does not directly affect the output; in all cases it is defined as 10 mV/C (independent of Vs). The accuracy given in the datasheet is based on a Vs of 5V.

    2) Yes, the relationship is the same.

    3) The diodes both have Vf of 1-V which is plenty of room for the negative rail of Vout, which goes down to -400 mV.

    4) If you are using a single supply, you will use the configuration shown in Figure 18 to create a negative voltage with respect to ground, and use a differential measurement.

    Please check out the TMP235, which TI recommends as a high-accuracy analog temperature sensor which works with a single-ended supply and has 10 mV/C sensor gain.  You do not need the diodes or a negative supply rail to use this part to sense the entire temperature range.

    Regards,

    Audrey