TMP236: Output voltage is too high

Giuseppe Modugno70

Part Number: TMP236

I'm using SOT32 TMP236 analog temperature sensor. I mounted it with long pins far from the PCB to avoid heating from other components on the board. So the sensor is now "floating" in the air.

The output voltage is around 1.0V (35°C), but it is too high for the ambient temperature that is around 25°C.

So I don't understand. Does TMP236 measures junction temperature or ambient temperature near the sensor? Is it possible that the air temperature near TMP236 is 5°C higher than the room temperature far from the sensor, because of self-heating of the IC? If this is the cause, how could I compensate this to have the room temperature? Is it a constant offset voltage (always 5°C at 0°C or 50°C), is it a propotional offset (maybe 1°C at 0°C and 10°C at 50°C)?

I'm supplying the sensor with 5V and the output is now left open, but it does not change if I connect an RC filter and an ADC.

over 3 years ago

0 Ren Schackmann over 3 years ago

TI__Mastermind 35825 points

Hi Giuseppe,

I wouldn't expect self-heating to cause 10C of error. I think you may have damaged your TMP236 while mounting it on those leads. Have you observed this problem on more than one sample?

thanks,

ren

0 Giuseppe Modugno70 over 3 years ago in reply to Ren Schackmann

Prodigy 100 points

I thought the same thing, so I replaced the IC with a new one, but the result is the same.

The temperature I calculate from the output voltage is higher than the real ambient temperature, the difference is around 5-7°C.

If I put a fan near the sensor, the output voltage from the sensor decreases and stabilize to a level that is much more similar to the ambient temperature.