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gommel
gommel
Associate II
June 2, 2008
Question

Using USB with internal Oscillator possible?

  • June 2, 2008
  • 3 replies
  • 706 views
Posted on June 02, 2008 at 17:01

Using USB with internal Oscillator possible?

    This topic has been closed for replies.

    3 replies

    gommel
    gommelAuthor
    Associate II
    May 17, 2011
    Posted on May 17, 2011 at 12:35

    Hello,

    we develop a very small and cost sensitive circuitry that is a USB device. Looking for affordable and small resonators/crystals we considered to use the internal oscillator of the STM32F203T8 instead. Is this possible and reliable enough?

    jj_it
    jj_it
    Associate II
    May 17, 2011
    Posted on May 17, 2011 at 12:35

    Years past we had similar issue while attaching 2 micros

    via Uart. Equation uncovered acceptable variance between

    the ''fastest'' sender versus the ''slowest'' receiver.

    However - the issues of temperature and aging also arose.

    Crystal & resonator solved this in the past - I especially

    like lanchon's 32Khz xtal ''reference'' suggestion. It's

    unfortunate that ''normal'' xtals for STM32 are BIGGER than the micro...

    lanchon
    lanchon
    Associate III
    May 17, 2011
    Posted on May 17, 2011 at 12:35

    USB full speed requires crystal. (I think the stm32 can't do low speed.)

    maybe you could run at 48MHz from HSI+PLL, while continually calibrating in software from LSE running a 32KHz crystal (these are cheaper, aren't they?), but you may have too much jitter.

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