There are advance control timers in STM32 family as in STM32F407 and these are specially suited for 3-phase (or 1-phase also) motor control applications using full H-bridge. These timers provide complementary output signals to drive the upper and lower h-bridge switches. This much is understandable from the datasheets. But there is a 'Channel 4' which is also available in these timers without the complementary output as shown in the image. I wonder what is the purpose of this timer?
closed as primarily opinion-based by Chris Stratton, berendi, Dwayne Reid, Bimpelrekkie, Edgar Brown Feb 25 at 17:11
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This is a general purpose MCU with general purpose peripherals, such as TIM1 and TIM8. While it might be well suited for the motor control application by having complementary outputs, it doesn't mean this is the only application this timer can be used for. Some application can benefit from having four input capture channels for example. If the fourth channel is not needed in your application, just leave it unused then.