AN2680 Datasheet, PDF (1/15 Pages) STMicroelectronics – Fan speed controller based on STDS75 or STLM75 digital

AN2680
Application note
Fan speed controller based on STDS75 or STLM75 digital
temperature sensor and ST72651AR6 MCU
Introduction
This application note describes the method of defining the system for regulating the speed
of the 5 Vdc fan using an ST72651AR6 microcontroller and digital temperature sensor
STDS75 or STLM75.
The sensor measures the temperature data and communicates this data to the
microcontroller. Based on this temperature data, the microcontroller issues a PWM signal
with varying duty cycle to the fan for regulating its speed.
The key features of the system are:
● Microcontroller with I²C interface and PWM peripheral to communicate with the sensor
and for regulating the fan speed
● Digital temperature sensor to measure the ambient temperature
● 5 Vdc fan to show the speed regulation
Section 1 highlights the features of the STDS75 or STLM75 sensor and explains its
interfacing with the microcontroller. Section 2 explains BLDC fan management and PWM
signal control to regulate the fan speed. Section 3 focuses on the hardware setup and in
Section 4 the application flow of the system is defined.
February 2008
Rev 1
1/15
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