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LMK03328: Unused VDDO_x pins

Guru 19775 points
Part Number: LMK03328

Hi Team,

Please advise us how to treat the unused UDDO_xx pins.

If the CLKOUT0/1 is only used, user would apply 3.3V or 2.5V or 1.8V to VDDO_01.

Can we leave other VDDO_xx pins floating, which are supplies for unused CLKOUT channels ?

Best Regards,

Kawai

  • Hi T.K,

    From LMK03328 datasheet "Outputs 0 and 1 share an output supply (VDDO_01), as well as outputs 2 and 3 (VDDO_23). Outputs 4, 5, 6, and 7 have individual output supplies (VDDO_4, VDDO_5, VDDO_6, VDDO_7). Each output supply can be independently set to 1.8 V, 2.5 V, or 3.3 V. When a particular output is desired to be disabled, the bits [5:0] in the corresponding output control register (R31, R32, R34, R35, R37, R39,

    R41, or R43) should be set to 0x00. If any of outputs 4, 5, 6, and 7 and their output dividers are disabled; their corresponding supplies can be connected to GND."

    It seems VDDO_4, VDDO_5, VDDO_6, VDDO_7 could be grounded.

    I have invited an expert to clarify it. Thanks for your patience.

    Regards,

    Shawn

  • I recommend to power all VDDO supplies and disable the unused output drivers by programming.  The disabled outputs will consume negligible current.

    Alan

  • Hi Alan-san, Shawn-san,

    Thanks of your support.

    Alan-san,

    Could you please tell us why you would recommend to power all VDDO supplies, instead of tying to GND ?
    It would be helpful for us to understand clearly.

    Best Regards,
    Kawai
  • PDN pin has an internal pullup to VDDO01.  If VDDO01 is grounded, the part would not start up.  Also, the device was characterized with all VDDOs powered, so its better to avoid risk by not deviating from this.  Anyway, VDDO draws minimal current when the unused output drivers are powered down.

    Regards,
    Alan

  • Hi Alan-san,

    Thanks for the information.

    Best Regards,
    Kawai