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CDCM61002: unstable frequency output

Elian Samaan
Prodigy 10 points
Part Number: CDCM61002
Other Parts Discussed in Thread: OMAP-L138

I am using 25MHz  quartz crystal and strapped the chip configuration to output 100MHz CLK. The chip works as expected for a while but the issue seems to occur most if I recycle power to the chip after operating for a while then the output frequency changes from 100MHz to approximate 115MHz. Any idea of what may have caused this frequency change?

Note: Same behavior was captured on multiple units that uses the same configuration. Circuit is equivalent to the one used on the OMAP-L138 Development Board. http://www.ti.com/tool/TMDXLCDK138#technicaldocuments

  • 0
    TI__Genius 11900 points

    Hello Elian,

    Here are a few things to look at:

    Can you please double check that you are following the "Power-Supply Filtering"  and "Start-up Time Estimation" provided on the datasheet.

    Also do you consistently see the same output frequency (~ 115 MHz) that you mentioned with each power cycle?

    How long do you wait between power cycles?

    You mention that you are following a circuit equivalent to the OMAP-L138. Is it safe to assume you are using the same pull-ups/pull-downs on pins 10,11, 13, 14, 15, 25 and 26? Are the same resistor values being used?

    Thanks,

    Vibhu