Hello. We use stm32f405 and voltage 1.9 V. At this voltage, timer 8 does not generate PWM at a frequency of 12 MHz. At a voltage of 3.3 V, the generation works.

[NOley]

Using HAL and CubeMX. APB2 72 Mhz. The timer prescaler is 0, the period is 5, the duty ratio is 50%. How to solve this problem?

[waclawek.jan]

Does the output pin drive something? Is the power supply stable enough, all power AND ground pins (including VDDA/VSSA) connected properly, decoupled, no bad solder joints? Doesn't the mcu reset itself? If you toggle the same pin set as GPIO "manually" in a loop, does it work as expected?

JW

[NOley]

pin clocks another chip. everything is stable, everything works, mcu is not reset. The problem was different, the pin speed was low, but needed medium. It is strange that when low everything worked at 3.3 V

[waclawek.jan]

Ah, so there *was* PWM output, just the other circuit was not satisfied with the slow slew rate, correct?

If you look at the datasheet, Table 50. I/O AC characteristics , you'll see how the rise/fall times are dependent on the power supply voltage. This is a basic effect in CMOS; the underlying reason is that the output MOSFET transistors don't work in full saturation and the lower the gate voltage the higher is the channel resistance.

Please mark your post as "Best" so that the thread is tagged as solved.

JW