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TI Home » TI E2E Community » Support Forums » Clocks & Timers » Clocks & Timers Forum » CDCE62005 practical questions about EEPROM, Loop filter and other things
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CDCE62005 practical questions about EEPROM, Loop filter and other things

CDCE62005 practical questions about EEPROM, Loop filter and other things

This question is answered
Fritz
Posted by Fritz
on Mar 22 2012 16:12 PM
Expert4370 points

Here a Q&A that might be helpful to others:

1) Can the CDCE62005 be purchased preprogrammed to a setting of our choosing?

Yes, through Avnet, who is setup to do this programing for this device.  

5) On my design I will not use the secondary input port, what does TI prescribe for tying this unused
port off?

You can disable this input and tie it to GND through a pull-down of a few kΩ on each input leg.


7) Why does TI recommend Y5V vs X7R caps on pins 4 & 38.

The capacitors need to have a particular ESR. I assume we are looking for a low ESR for the internal regulator.



8) What is the range of loopbandwidth (low to high) that I can set the filter to while running at 500MHz with a 25MHz xtal on the aux.
note: my study shows that the range is a function of settings and that the range with my settings ~65kHz=>1GHz.

Loop bandwidth ranges from 30Hz up to fPFD/10, but you should not aim for anything higher than 500kHz. For a 25MHz XTAL, I would recommend aiming for 300kHz (maybe also try 400kHz, as you can all these values by simply using the internal loop filter and reconfiguring).



9) How shall I go about choosing the optimal setting? There are many?

Target the following:

BW=300-400kHz

Phase Margin= aim for 60-70 (65 is great)

Gamma= make it at least one, 10 is best, make it less than 100 I’d say

R3: minimize (e.g. 5k)

C3: set it such that 3rd pole is at least 10x higher than BW (e.g. 3MHz); If in doubt, minimize C3

C1: don’t use less than 10pF

C2: I would use max value at 473.5pF

R2: set it such that you get the right BW, likely 4k or 9k  

ICP: make it at least 300uA, I would aim for 600uA if possible with the combinations of the other components.

Here is a setting that would be really good:



10) Is the GUI setup software stable?

YES



11) Can I run the TI setup software with another host adaptor (someone elses spi port tool)?

Not easily, because the GUI tries to access a particular driver inside the USB receiver and there is no documentation how to do this.



12) Can TI recommend a SPI tool?

We do have stand-alone USB dongles that can convert USB into SPI and use the driver from our EVM I believe.

Most customers write their own SPI sequence with a controller.

CDCE62005
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  • Fritz
    Posted by Fritz
    on Mar 22 2012 16:13 PM
    Verified Answer
    Verified by Fritz
    Expert4370 points

    ok

    Report Abuse
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