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How to synchronize multiple AD9125 when using NCO modulation?

Question asked by colorjun on Jul 13, 2012
Latest reply on Jul 27, 2012 by YiZ

Hi, I'm using multiple AD9125 to generate signals at 70MHz. I use 4× Interpolation 400MHz directly for fDAC and 100MHz for fdata. Digital datapath is PREMOD HB1 NCO , HB2 HB3 bypassed. I use FIFO Rate Synchronization,the DACs output skew to vary from power-on to power-on. BUT when I bypass the NCO and use 560MHz for DAC and 140MHz for fdata the output 70MHz are synchronized. So I think the problem is the NCO of AD9125s are not synchronized. NCO is reset on the first extended FRAME pulse after reg 0x36 bit 4 transitions from 0 to 1. But the FRAME pulse is generated by FPGA can not synchronize with the SYNC_CLK.
In this case how to make the NCOs and outputs synchronized?

Thanks

JUN

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