AN3397

Temperature sensor overview

Doc ID 018809 Rev 1

5/24

1

Temperature sensor overview

This section provides an overview of the temperature sensor (TS) embedded in

STM8L15xxx devices. It describes how the TS works, the data processing required, and the

accuracy that can be expected.

1.1

Temperature sensor

The STM8L15xxx built-in TS is based on a semiconductor diode embedded in the MCU.

The sensor provides an analog output voltage proportional to the junction temperature of

the device.

Note:

The temperature information provided by the sensor is the thermal junction temperature

(temperature of the semiconductor), and may differ from the ambient temperature (MCU

package).

The diode bias current is held as constant as possible. Consequently, the forward bias

voltage across the diode is temperature dependent, with a temperature coefficient of about

1.62 mV/°C (see the device datasheet). The TS provides a reasonably linear characteristic

with a typical deviation of ±1 % (±2 % max) from linear asymptotic functions and a

temperature range equal to that of the device (-40 °C to 85 °C).

The sensor provides good linearity but quite poor interchangeability, and must be calibrated

to obtain good overall accuracy. If the application is designed to measure only the relative

temperature variations, the temperature sensor does not need to be calibrated.

1.2

Temperature measurement and data processing

The TS is internally connected to the ADC_TS channel of the analog-to-digital converter

(ADC), which is used to sample and convert the sensor analog output voltage. The raw ADC

data must be further processed to display the temperature in standardized units of

measurement (for example, Celsius, Fahrenheit or Kelvin)

operated applications, it must be measured to obtain a correct overall ADC conversion

range. To easily measure the power supply voltage, we recommend using the embedded

internal reference voltage (bandgap). The device is well calibrated during the manufacturing

process, and its calibration data is stored in the protected memory area at address 0x4910.

Note:

Check that the bandgap factory calibration data (VREFINT_Factory_CONV) is available

from your STM8L15xxx MCU device.

The embedded bandgap voltage calibration data is a 12-bit unsigned integer acquired by