Skip to main content
Visitor II
November 14, 2022
Solved

I'm looking for STM32G Series product.

  • November 14, 2022
  • 3 replies
  • 1728 views

Hello?

As title, I want to know product with USB, FD-CAN, 2~3 DAC, etc.

Problem is USB and HCLK are bound(using external clock), so that upper limit is determined to be low.(48, 96, 144 MHz in maximum 170 MHz)

For that reason, to ask the question, is there a product that has USB+FD-CAN and separated PLLSAI in 32~48 pins package?

Please reply.

    This topic has been closed for replies.
    Best answer by LSung.1

    The reason you want 64 or 128 or 256 is that the division of SPI can only be done in multiples of 2. If it is 96 or 144, the undesirable reason is that the result does not come out as an integer multiple of 1 MHz when dividing by 128 or by 256.

    In addition, RC oscillators are to be avoided because they do not guarantee an accurate frequency.

    Neither is important, but I was asking to see if there was a product that would fit both.

    3 replies

    Super User
    November 14, 2022
    LSung.1Author
    Visitor II
    November 16, 2022

    I want to make 48 Mhz in USB and 64 MHz(or 128 MHz) in HCLK using ​external crystal.

    ​​If I don't make it separately, I can't make it this way.

    As an aside, CUBE doesn't search because it has a DAC. There seems to be an error in MCU/MPU Selector of STM32CubeIDE.

    Graduate II
    November 15, 2022

    Why for USB you cannot use HSI48 with clock recovery from USB SOF sequences?

    LSung.1Author
    Visitor II
    November 16, 2022

    I don't know that clock recovery. I think I need more study.

    Is it correct to synchronize with the external clock?

    Graduate II
    November 19, 2022

    > 64 MHz(or 128 MHz) in HCLK

    So 96 or 144 MHz is too low, but 64 or 128 MHz is OK?

    > Is it correct to synchronize with the external clock?

    Why would ST put in such a feature? Generally there are two ways how to make 2 frequencies almost the same. Either you make both of those accurate to some defined specification, or one of those synchronizes to the other.

    LSung.1AuthorAnswer
    Visitor II
    November 21, 2022

    The reason you want 64 or 128 or 256 is that the division of SPI can only be done in multiples of 2. If it is 96 or 144, the undesirable reason is that the result does not come out as an integer multiple of 1 MHz when dividing by 128 or by 256.

    In addition, RC oscillators are to be avoided because they do not guarantee an accurate frequency.

    Neither is important, but I was asking to see if there was a product that would fit both.

    Graduate II
    November 22, 2022

    > RC oscillators are to be avoided because they do not guarantee an accurate frequency.

    That's why HSI48 oscillator has a synchronization feature on USB SOF.

    > does not come out as an integer multiple of 1 MHz when dividing by 128 or by 256

    Why is that necessary?