Introduction

The STM32WB Series microcontrollers have internal RC oscillators that can be selected as the system clock source. These are

known as the HSI16 (high-speed internal 16 MHz) and MSI (multi-speed internal) oscillators.

The operating temperature has an impact on the accuracy of the RC oscillators. At 25 °C, the HSI16 oscillator has a nominal

accuracy of 0.25%, but in the temperature range of -40 to 105 °C, the accuracy decreases.

To compensate for the influence of temperature on internal RC oscillators accuracy, the STM32WB Series microcontrollers have

built-in features to allow users to calibrate the HSI16 oscillator and to measure the LSI (low-speed internal) oscillator frequency.

This application note focuses on how to calibrate STM32WB Series internal RC oscillators using the X-CUBE-RC-CALIB

software. The HSI48 can also be trimmed even if it cannot be selected as the system clock.

The calibration of the external HSE oscillator is covered in HSE trimming for RF applications using the STM32WB Series

application note (AN5042).

All the methods presented require an accurate reference signal.

The measurement of the LSI oscillator is performed by connecting the oscillator to a timer input capture.

Using X-CUBE-RC-CALIB software to calibrate STM32WB Series internal RC

oscillators

AN5282

Application note

AN5282 - Rev 1 - June 2019

For further information contact your local STMicroelectronics sales office.