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Crystal frequency stability and tolerance for OSC0 on AM3352

Nomo
Guru 16800 points
Other Parts Discussed in Thread: AM3352

Hello,

In "Table 4-2" of AM3352's datasheet, "Crystal frequency stability and tolerance" is plus or minus 50ppm.
Does this parameter mean the sum of crystal frequency stability and tolerance?
I think that the crystal frequency stability is plus or minus 50ppm and the tolerance is plus or minus 50ppm.

Best Regards.

Nomoto

  • 0
    TI__Guru**** 393215 points

    Hi Nomoto-san,

    The 50ppm limit is the total of tolerance + stability, where tolerance is the initial accuracy of the crystal with the specified load capacitance and stability is the combination of frequency change across operating temperature plus frequency change due to long-term aging.

  • 0 in reply to Biser Gatchev-XID
    Guru 16800 points

    Hello Biser-san,

    Thank you for your reply.
    However, I think it's too hard to satisfy the specification, if the device will have worked so long time.
    What happen when the crystal frequency stability and tolerance is over plus or minus 50ppm?

    Best Regards.

    Nomoto

  • 0 in reply to Nomo
    TI__Guru 59285 points

    I just did a quick search and found the CTS Series 445 crystals have a standard frequency tolerance of +/- 20 ppm and standard frequency stability of +/- 30 ppm.

    This requirement is primary driven by peripherals that communicate with other devices via a serial interface.  In most cases these serial interfaces must transmit data at a specific rate.  For example, the RMII specification which defines the interface between a Ethernet PHY and MAC states the RMII reference clock must be +/- 50 ppm.  Serial interfaces specifications define clock frequency limits so designers know how to size elastic buffers to allow small differences in transmitter and receiver data rates.  If you allow the reference clock to exceed these limits, it may be possible to over-run internal FIFOs if the transmitter is operating too fast or receiver is operating too slow.

    Regards,
    Paul