Encoder index / HRTIM in H7 or F7

[JHONG.1055]

Hi there,

1.

My first question is about encoder index.

I know that encoder index(so called Z pulse) is applicable in G4 series. (RM0440 1,109 pages)

However I can't find that feature in any of H7 and F7 sereis.

2.

I know that the maximum resolution of HRTIM in G4 is ​184 ps resolution. (RM0440 801 pages)

However, in H7 series such as H743, the maximum resolution is 2.1ns even though the clock of H7 is more faster than G4. (I found that the CKPSC[2:0] values from 000 to 100 are reserved in H7.)

My project is motor control and DC/DC converter(up to 1MHz switching with duty control) and I considering to use m7 core because of computing power.

Are the G4 series the best for my project or is there a more suitable one?

3.

Similar question.

What is the best MCU in ST that can be used for motor control and DC / DC converter control?

My project require much computing power.

[Vincent Onde · Accepted solution]

​Hi,

For the point 1 on encoder index, this is a new feature of the timer, and the STM32G4 is the first one to embed it. It was not available when the F7 and H7 were designed. This is now being deployed in new STM32 product lines.

For the high resolution, point 2, the HRTIM version in the H7 does not feature the high-resolution part of the timer, with DLLs, which allows to have a 32x ratio vs clock speed. We just have the part of the timer clocked by the 480MHz, therefore the 2.1ns (and the limited range for CKPSC).

For a 1MHZ DC/DC converter, the STM32G4 will be more suitable, as it will offer 5440 steps for duty cycle programming (~12.4-bit). The H7 will provide 480 steps (~8.9 bit), and this could (eventually) lead to limit cycling issues.

This being said, the H7 is definitively more powerful, if you have to do both motor control and DC/DC, and it's dual core architecture will be beneficial to isolate these two real-time critical tasks.

Best regards,

Vincent