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According to the datasheet the maximum rating of the output of an LM35 is 6 V.

However, the output should give 10 mV/C and it supports upto 150 C, which results in 10 mV/C * 150 C = 1500 mV which is 1.5 V. In what cases it will deliver more than 1.5 V?

Update

I initially added a statement that the output should not be connected to a 3.3 V ADC. However, it seems this is not the case, still my question stays, how can the output be 6 V?

Excerpt from LM35 datasheet:

enter image description here

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    \$\begingroup\$ Where did you read that? \$\endgroup\$
    – CL.
    Commented Feb 7, 2019 at 12:31
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    \$\begingroup\$ Yes, we need to see the context of the warning that you mention. Please provide a link to the source of those statements. \$\endgroup\$
    – Elliot Alderson
    Commented Feb 7, 2019 at 12:33
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    \$\begingroup\$ The datasheet says that its operating range is 4-30 V. \$\endgroup\$
    – Dave Tweed
    Commented Feb 7, 2019 at 12:39
  • \$\begingroup\$ @CL. / Elliot Alderson ... I misread it, it was about the input voltage, and also the voltage dividers where not specifically for the LM35. However, still my question exists why I can get 6V? It will ruin my STM32 ADC which can handle only 3.3V. \$\endgroup\$
    – Michel Keijzers
    Commented Feb 7, 2019 at 12:45

1 Answer 1

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The output voltage as a function of temperature is with respect to the GND pin of the sensor. This voltage cannot exceed 1.5V in normal operation.

The maximum output voltage spec of -1V to 6V is with respect to circuit ground. The GND pin of the sensor is lifted above circuit ground in certain applications, such as to convert the sensor output voltage to a voltage proportional to Fahrenheit temperature. Take a look at the system examples given in the data sheet. The example circuit shown below is an example from the linked data sheet.

enter image description here

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  • \$\begingroup\$ Is this voltage lift also applicable for negative values? \$\endgroup\$
    – Michel Keijzers
    Commented Feb 7, 2019 at 13:05
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    \$\begingroup\$ I was curious to see the Celcius to Fahrenheit converter using electronic components, that's pretty amusing. (I also added it to the answer, hope you dont mind). \$\endgroup\$
    – Wesley Lee
    Commented Feb 7, 2019 at 13:07
  • \$\begingroup\$ Don't use an image unless you make it very clear where you got the image. I added a sentence to clarify that. \$\endgroup\$
    – Elliot Alderson
    Commented Feb 7, 2019 at 13:10
  • \$\begingroup\$ I added a new question about the diodes related to the system applications you refer at: electronics.stackexchange.com/questions/421011/… \$\endgroup\$
    – Michel Keijzers
    Commented Feb 7, 2019 at 13:13
  • \$\begingroup\$ What does circuit ground have to do with anything if the circuit ground isn't actually connected to the device anywhere? I don't follow how some arbitrary reference voltage relates to the absolute maximum ratings of the device. Surely only the currents and voltages inside the device itself can damage it? \$\endgroup\$
    – Hearth
    Commented Feb 7, 2019 at 15:22

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