L6235 speed control using PWM

Thread Starter


Joined May 28, 2024
I am trying to control the speed of brushless DC motor by providing a PWM signal from a STM32 micro to the Vref pin of L6235 as shown below. My motor has a 1/156 gear ratio. When I apply the variable PWM to the VREF pin, it doesn't change the speed instead the motor keeps rotating and makes a huge noise. What I am missing here?

L6235 app note: https://www.st.com/resource/en/appl...shless-dc-motor-driver-stmicroelectronics.pdf
circuit diagram: https://download.mikroe.com/documen...2_click/brushless-12-click-schematic-v101.pdf



Joined Mar 14, 2008
Your capacitor may not be large enough.

What is the switching frequency of you PWM signal?
With those values for RLP and RDIV, CLP should be a minimum of FPWM / 100kHz * 10nF where FPWM is your PWM switching frequency.