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Alternative to the use to the CDCE62002

shadders
Expert 1065 points
Other Parts Discussed in Thread: CDCE62002, PCM1792

Hi,

I have implemented the CDCE62002 in a design that uses two references - one crystal oscillator as the CMOS input, and another crystal using the CDC62002 oscillator circuitry.

The two frequencies are do not share any common factors, hence the use of two crystals.

Hence i am using the CDCE62002 to provide clocks based on either input.

The performance of the CDCE62002 is a sub Picosecond jitter.

Since i wish to use two distinct frequencies with low jitter clocks, is there an alternative way of providing the two frequencies from simple crystal oscillators that exhibit the same low jitter ?.

I could employ logical switching to distribute the clock to the relevant IC.

I ask this as i cannot find any literature for clock generation that does not employ phase locked loops (PLL).

Are there any circuits that use crystals, and from memory, such as a simple inverter, that produces sub-picosecond clock jitter ?. is only a single freuqency is required and that frequency is available as a crystal ?

Can sub-picosecond clock jitter only be provided by CDCE62002 family IC's ?

Arte there clock multipliers that provide the same low jitter (sub-picosecond) that can be used ?

Thanks in advance for any guidance,

Regards,

Richard.

  • 0
    TI__Genius 13335 points

    Which clock frequencies are you trying to generate?

    If you use low frequency oscillators or crystals to generate higher clock frequencies, you must use a PLL.

    Alternatively, you can use two high frequency oscillators and a multiplexer to choose one of the frequencies. Typically a good quality crystal oscillator comes with sub-picosecond jitter.

  • 0 in reply to Luke LaPointe
    Expert 1065 points

    Hi Luke,

    Thaks for the reply.

    I am trying to provide a clock frequency that is either a multiple of 44.1kHz or 48kHz.

    The Texas PCM1792 chip can accept greater than 30MHz clock signals, and as such i was thinking of using higher clock frequencies which may be difficult to obtain as an oscillator frequency.

    I have seen oscillators with sub-pico second jitter - but for the 44.1kHz frequency, obtaining a multiple of one of these at a frequency in the 30MHz+ range is generally difficult.

    I researched for sub picosend oscillators and located some manufacturers, but again the 44.1kHz factor is difficult to obtain.

    I think the CDCE62002 is the best option, but i did have great difficulty in placing the chip on the PCB.

    Thanks again for the reply,

    Regards,

    Richard.