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AFE7950: Power Supply for SYSREF+/- Input

Jack Zhang
Intellectual 540 points

Part Number: AFE7950
Other Parts Discussed in Thread: LMK04832

Hello, I'm looking at the AFE79XX_schematic_layout_checklist, and for the SYSREF clock input, the notes state that common mode needs to be set externally to 0.6 V. I plan on using the LMK04832 as a clock generator with a 3.9 MHz LVDS output feeding into the AFE7950. What power supply should I be referencing for a voltage divider network on the positive and negative terminals of the SYSREF signal? Does TI have a recommended approach? Is AC-coupling encouraged? Thank you for you time.

  • 0
    TI__Genius 11115 points

    Hi Jack,

    The voltage divider circuit that sets SYSREF common mode voltage is recommended to reference to VDD1P8PLL supply. AC-coupling SYSREF is supported. However note that if NCO phase across multiple devices have to be synchronized, NCO frequency has to be a multiple of the SYSREF frequency when using continuous SYSREF. 

    Regards,

    Vijay