This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMK01801: Interfacing with AD9783 - from Analog Devices

Part Number: LMK01801


Hi,

We want to interface LMK01801 with AD9783 - from Analog Devices.

Input clock frequency is roughly 1.32G and the output frequency from LMK01801 - 94.2 MHz going to AD9783.

Now my question is AD9783 has an input side termination of 50 ohm pulled upto common voltage of 400mV and Differential Peak-to-Peak Voltage (CLKP − CLKN) = maximum of 1.6V.

Now my doubt is at given common mode voltage of AD9873, what will be the maximum value of Vod generated from LMK01801 i.e. the output differential voltage. Whether it can cross the limits of AD9783? Or whether there is a problem in my understanding?

I will be thankful if I get quick help on this.

Regards.

  • Please reply urgently.

    Regards
  • If the schematic is copied from the AD9783 datasheet, it shows the clock output being AC coupled to the 50 ohm termination resistors and the AD9783 input. This suggests that any clock format can be used regardless of Vcm (because it's AC coupled) provided that:
    1) The swing of the output is in the acceptable range, which is quite wide. Vid = 0.2 V to 1.0 V, traditional LVDS and LVPECL both are in this range.
    2) When AC coupled, the only thing which could impact the Vcm is if the duty cycle is poor. But a nominally 50% duty cycle will have no problem.

    It's ok to interface LMK01801 to AD9783. Be sure to AC couple as recommended by AD9783 datasheet.

    73,
    Timothy