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TSW40RF80EVM: Trying to synchronize RF DAC outputs across multiple TSW40RF80EVM boards

Part Number: TSW40RF80EVM
Other Parts Discussed in Thread: DAC38RF80, LMK04821, LMK04832EVM


We are trying to synchronize RF DAC outputs across multiple TSW40RF80EVM boards.

1) This is what we have done successfully.  Initially, using a single TSW40RF80EVM board with the default config file (2T2R_RevC_ConstInput_12xDec_18xInt_2949p12M_4915p2Gb.cfg) supplied with the TI GUI, we have set up the  DAC A and DAC B outputs of the  onboard DAC38RF80 outputs as 50MHz tones. Looking at the DAC outputs on a CRO reveals that the two tones have a fixed phase relationship, as wanted.

2) This is where we have  a problem.  However when we take tones off two separate TSW40RF80EVM boards, using a 10MHz sinusoidal clock through a splitter to the CLKIN0 input of the LMK04821 chip on each board, we observe on the CRO a phase jitter between the two RF tones. See attached video.

We are unsure exactly what is causing this jitter. The only connection we have between the two boards is the 10MHz clock.

We are not sure what to do about SYSREF. There is no obvious SYSREF input on the TSW40RF80EVM.

3) This is what we plan to do to extend to multiple TSW40RF80EVM boards.  We plan to use a  LMK04832EVM as a clock generator for multiple TSW40RF80EVM boards. Again, we are not sure what to do with the SYSREF outputs from that LMK04832EVM.

Any suggestions on removing the jitter on the signals between boards would be welcome.

Also any comments on the multiboard setup using the LMK04832EVM as a clock generator.