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Original question:

LMK04828: LMK04828 1.8V IO support

LMK04828: Independence of Vcc5_DIG, and Vcc1_VCO and Vcc6_PLL

James Peterson
Prodigy 30 points
Part Number: LMK04828

Can the Vcc5_DIG input voltage be run completely independently of the other "low crosstalk" supply pins, Vcc1_VCO and Vcc6_PLL1?  We are interested in using 1.8V SPI interfaces, since our FPGA has many more available IO pins.  I just wanted to confirm there was no other dependencies between these Vcc pins, (if they are properly decoupled), since they tend to be connected at the same potential on most evaluation board schematics.  Thank you.  

  • +1
    TI__Mastermind 33700 points

    Every supply pin on the LMK04828 must be connected to 3.3V. This is not optional.

    All LMK04828 digital inputs accept 1.8V I/O, so your 1.8V SPI would still work. You can even get readback working, as long as the LMK04828 SPI output pin is configured as an open-drain output and uses a pull-up to a 1.8V I/O supply - see the SDIO_RDBK_TYPE, PLL1_LD_TYPE, PLL2_LD_TYPE, etc. fields in the register map.