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CDC6C: Drop in Replacement Issues

Jason Maxwell
Intellectual 1605 points

Part Number: CDC6C

Hi Team,

My customer is looking to use our 25MHz and 12.288MHz oscillators in the CDC6C family as a drop-in replacement for the ECS-2333-12288-BN-TR. They started testing them yesterday by dropping them on a board. 

However, neither of the oscillators worked. The outputs were high. The customer is suspicious of the drive ability of the oscillator. Another possibility is that they have the power fed through a 1k ferrite bead and it has a 0.1uF to ground. They were able to breadboard one of the oscillators and got an output so it is working independently.

Any thoughts on what might be going on?

Best,

Jason Maxwell

  • 0
    TI__Intellectual 1605 points

    In Addition, the customer is looking for the drive output specification. Could you help point me towards this? I am not able to find it in the datasheet.

    Best,

    Jason Maxwell

  • 0 in reply to Jason Maxwell
    TI__Genius 15010 points

    Hi Jason, 

    In the CDC6C datasheet, we specify a maximum capacitive load of 30pF on the output for frequencies below 50MHz. If the customer is driving a resistive load, the output amplitude will also be reduced since the load will behave like a voltage divider with the CDC6C's 50 Ohm output impedance. 

    It does seem odd that the output is stuck high. I don't suspect that the power supply filtering is causing any issues as long as CDC6C is seeing 3.3V at the VDD pin. Just to clarify, the ferrite bead has 1k Ohm impedance at a high frequency and not at DC, correct? And can you share a schematic of the input termination at the receiver? 

    Regards, 

    Connor 

  • 0 in reply to Connor Lewis
    TI__Intellectual 1605 points

    Hi Connor,

    The OUT goes to the AK7738 XTI pin at the receiving end. I couldn't find a specified capacitive load on the XTI pin in the AK7738 datasheet. And yes the ferrite bead has 1Kohm impedance at 100MHz, not DC. To reiterate my email they were able to get the clock working, as it seemed to be a setup problem.

    Best,

    Jason

  • 0 in reply to Jason Maxwell
    TI__Genius 15010 points

    Jason, 

    Thanks for the update. I'll go ahead and mark this thread as resolved since they were able to get the clock output to work.