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CDCE913: Output 2 channels 24MHZ for CDCE913

Mickey Zhang
Genius 12080 points
Part Number: CDCE913


Hi team,

The customer would like to use CDCE913. The input frequency is 24MHZ. He wants to output

2 channels 24MHZ. But he found the device only outputs 1.7MHZ and the output waveform is irregular.

Q1. Can CDCE913 achieve the customer's function?

Q2. If it can be, please check the attach for the customer's schematic and his output waveform.

Would you check if the customer's schematic is correct?

  • 0
    TI__Mastermind 28021 points
    Mickey,

    According to the TI clock archtect tool and the datasheet, this seems like a valid thing to do.
    he VCO tunes 80 to 230 MHz and the VCO needs to be a multiple of the input frequency and this can be made to be true.

    Based on your result, I think there os some setup issue. Here are some things I see:
    1. I am perplexed in your schematic at the termination for Y3, as this is a CMOS output.
    2. Is there a way to see if the VCO is oscillating at the frequency that you think it should be? BTW, I found this reference as well (www.ti.com/.../scaa085a.pdf) regarding the VCO.

    Regards,
    Dean
  • 0 in reply to Dean Banerjee
    TI__Genius 12080 points
    Hi Dean,

    Thanks for your reply. But I don't quite understand what you mean.

    Q1. What do you mean by Y3?

    Q2. You mean let the customer to measure the VCO frequency? So, how to measure the the VCO frequency?
  • 0 in reply to Mickey Zhang
    TI__Mastermind 28021 points
    Mickey,

    Q1: Y3 is pin 8. I see it go through a path and have a resistor and capacitor to ground. But I think this is a CMOS output. This seems suspiciuous.
    Q2: I assume the output frequency is equal to the VCO frequency divided by some divide value, D. Multiply the output frequency by D to get the VCO frequency.

    Everything in the datasheet and application note seem to all be focused on 27 MHz. I note that their frequency is 24 MHz. I don't see anywhere in the datasheet where this violates specifications, but I don't see any other frequencies. You might also want to check pin 14 and see if indeed you are getting the 24 MHz you expect.

    Regards,
    Dean