TMP36 temperature sensor

The TO-92 analog temperature sensor, TMP36 style: three legs, no protocol, and a voltage that is the temperature.

Power it, and the middle leg sits at 500 mV at 0 degrees Celsius, moving 10 mV for every degree after that: 25 degrees is 750 mV, -10 degrees is 400 mV. That offset is the whole trick of the part: it lets a single-supply sensor read below freezing with no negative rail, and it is the thing every sketch using one gets wrong the first time.

Pins

Pin	What it does
VS	Supply, 2.7 V or more.
VOUT	offset + slope x temperature.
GND	Ground.

Properties

offset: 500 mV by default (a TMP36); set to 0 for an LM35, which has the same 10 mV a degree with no offset. slope: 10 mV per degree by default.

While it runs

Drag the slider on the part to change the temperature it sits in.

What the model gets right

Below 2.7 V across VS and GND the part is not running and VOUT is high impedance, exactly what an unpowered sensor does. The output is a low-impedance source clamped to the rails, so a sensor on a 3.3 V board cannot read above 3.3 V; the datasheet's 125 degree top of range simply is not reachable there, which is true of the real part too.

What it does not model

No self-heating, no settling time, no noise, and no datasheet accuracy error. The temperature you set is the temperature that comes back, which makes a demo a demo rather than a calibration exercise. A real TMP36 is ±1 °C at 25 °C and ±2 °C over its range, and the straight line here has none of that.

VOUT drives through 100 ohms, which is a stand-in rather than a datasheet figure: a real TMP36 has a much lower output impedance but can only source about 50 µA, and neither the impedance nor the current limit is what the number represents. It is there so a load on the output is not free. There is no supply-current draw, no supply rejection, and no way to overload the output. It simply behaves as a 100 ohm source however much current is taken from it.

Common mistakes

Forgetting the offset when converting the voltage back to a temperature. A sketch that assumes 0 V is 0 degrees, LM35-style, reads a TMP36 as 50 degrees too hot.

See it in action

Thermometer reads a TMP36 straight onto an LCD. Open it at /templates.