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CDCUN1208LP: CDCUN1208LP outputs Failing

Roberto Assiro
Prodigy 20 points
Part Number: CDCUN1208LP

I'm using CDCUN1208LP in PINS mode configuration. The input LVCMOS from a clock generator ABLJO-120 at 120 MHz is direct connected with input (lvcmos)

The device seems work fine, but if I turn off my board and then turn on it the CDCUN1208LP hangs and not output is provided on any output.

The failure continue for a long time, but if I keep the board off for 2 hours about the device works. Very strange.

I checked the power supply and 3.3V came before the 1.8V 

I prefer to use the device in pins configuration mode, but I can try to use it by I2C configuration if needed

Have someone any suggestions?

Thanks in advance

  • 0
    TI__Genius 16845 points
    Hi Roberto,

    When you turn off power to the CDCUN1208LP, is the input still being applied? The input voltage should never exceed VDD.

    Please confirm that you are using 3.3V for the core supply VDD and 1.8V for the output supply VDDOx. If so, your power supply sequencing is OK.

    What current consumption are you seeing when the CDCUN1208LP is active, and when it hangs?

    Kind regards,
    Lane
  • 0 in reply to Lane Boyd
    TI__Genius 16845 points
    Additionally, notice the VDD ramp requirement for pin mode (see Table Note 2 for Table 6.3): " A minimum VDD slew rate of 6500V/s should be obtained to ensure proper device functionality in Pin Mode." Please confirm that VDD slew rate meets the requirement.

    Kind regards,
    Lane
  • 0 in reply to Lane Boyd
    Prodigy 20 points

    Lane Boyd said:
    Additionally, notice the VDD ramp requirement for pin mode (see Table Note 2 for Table 6.3): " A minimum VDD slew rate of 6500V/s should be obtained to ensure proper device functionality in Pin Mode." Please confirm that VDD slew rate meets the requirement.

    Kind regards,
    Lane

    Thanks a lot Lane,

    on my board the VDD (for core) rise time at start is about 2ms. Too much
    I changed the capacitor to get less rise time under 500 us on output of the dc/dc converter 3V3. The problem is solved

    Regards 

    Roberto