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CC1200: DCPL_xxx pins of the CC1200

Nona
Intellectual 1730 points
Part Number: CC1200

Team,

My customer who develops the wireless product has started development for their own board using the CC1200. They tried mesurement the voltage of the DCPL_xxx pins since wants to investigate the effective capacity of the capacitor used in the CC1200EM when applying DC bias. The result of their approch would be as followings:
DCPL(pin#6): 1.769V
DCPL_VCO(pin#21):0V
DCPL_PFD_CHP(pin#26):0V
DCPL_XOSC(pin#29):1.778V

Is it expected result?
Or are both the DCPL_VCO and the DCPL_PFD_CHP applied in case of entering into other mode?
Could I have your comment on this?
Thank you.

  • 0
    TI__Guru**** 317180 points
    All of the DCPL pins are outputs from internal LDOs and need to be decoupled with a cap as described in the reference design.

    DCPL: Goes to the LDO that supplies the digital part
    DCPL_VCO, DCPL_PFD_CHP: Goes to two LDOs in the synth. The LDOs are turned on when the VCO/ synth is turned on.
    DCPL_XOSC: Supplies the xosc module and are on if the xosc is on.

    The output av all should be 1.8 V +/- ~5%

    Could you elaborate a bit more on what they want to do?
  • 0 in reply to TER
    TI__Intellectual 1730 points
    Hi TER,
    Thanks for your replay.

    My customer unfortunately cannot employ the components our reference design uses for new design due to their internal authorization. Therefore needs to know the effective capacity in order to look for another one (more small is better). I would say the effective capacity decreases when using small parts even it capacity value would be almost all same as our reference design.

    Could I have your advice how to keep RF performance in case of using small parts than our reference design?
    Thank you.
  • 0 in reply to Nona
    TI__Guru**** 317180 points
    Do you mean they need to go from 0402 to 0201 or smaller size caps?
  • 0 in reply to TER
    TI__Intellectual 1730 points
    Yes, they want to use it if possible.
  • 0 in reply to Nona
    TI__Guru**** 317180 points
    As I wrote, the caps connected to the DCPL pins are for decoupling of the internal LDO meaning that type and size of the cap should not be critical. If you find a 0201 cap with the same value as the 0402 that is used in the reference design, use this.