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 document details a method for defining a system to regulate the speed of a 5 Vdc fan. The system utilizes an ST72651AR6 microcontroller with I2C interface and PWM peripheral, communicating with either an STDS75 or STLM75 digital temperature sensor. Based on ambient temperature data received from the sensor, the microcontroller issues a PWM signal to control the fan speed.
The guide covers the theory of operation for both the digital temperature sensors (STDS75/STLM75) and BLDC fans. It explains hardware setup involving an N-channel power MOSFET for low-side drive and provides details on configuring sensor registers for alarm thresholds and oversaturation settings.
| Measurable temperature range | -55 °C to 125 °C |
|---|---|
| Sensor resolution (default) | 9 bits |
| Fan supply voltage | 5 Vdc |
| Microcontroller model | ST72651AR6 |
| MOSFET model | STB100NFO3L |
The system supports the STDS75 or STLM75 digital temperature sensor.
The microcontroller issues a PWM signal with varying duty cycle to the fan for regulating its speed.
The default resolution setting used in this application is 9 bits.