AnsweredAssumed Answered

AD9954: How to synchronize multiple chips with the same REFCLK

Question asked by luca.banchi on May 23, 2016
Latest reply on May 24, 2016 by LouijieC

Dear Support,


in my design, I want to synchronize multiple AD9954 chips placed on different boards sharing the same REFCLK at 400MHz (made by means of a clock distribution system).

In other words, 9 different boards share the same 400MHz REFCLK with the same phase, this clock is the REFCLK for the AD9954 placed on each board. All the AD9954 chips will produce the same output frequency at the same time. These output frequencies must have the same phase. During the operation the AD9954 chips will change the output frequency all-together by varying the FTWs, also in this case all the output frequencies must present the same phase.

My questions are:

1- using the same REFCLK with the same phase for each board, does it ensure that all the AD9954 output frequencies have the same phase.

2- regarding SYNC_CLK output and SYNC_IN input, how to connect those pins? Have I to connect SYNC_CLK out to SYNC_IN in on each AD9954?

3- When the AD9954 output frequencies are synchronized one to each other, will those frequencies still remain phase-locked when the FTW that control all the AD9954s changes?  In other words, if all the AD9954 are phase-matched, will this condition be preserved after a new FTW is written on those chips?

4- on page 14 of the AD9954 datasheet it is written that "...A control bit is provided to force the phase accumulator output to zero.". Can this functionality be used in order to get phase matching of the AD9954 chips with the same REFCLK?


Thank you