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LMX2594: The two LMX2594 cannot achieve 4-channel synchronous output

Amy Luo
Expert 6895 points
Part Number: LMX2594


Hi team,

One of our customers has the following questions：

Using two LMX2594, it is expected that the clock outputs of the two LMX2594 are RFoutA=5GHz，RFoutB=3.90625MHz (RFoutB is configured as SYSREF mode required by 204B bus), and the phases of RFoutA and RFoutB can be relatively fixed.

Set according to the datasheet of LMX2594, two RFoutA have been synchronized, but RFoutB cannot be synchronized, and when Repeater Mode is adopted, RFoutB will not output.

Please tell me how to set the register to realize the 4-channel output synchronization of two LMX2594, and make RFoutA=5GHz and RFoutB=3.90625MHz?

Best Regards,

Amy Luo

  • 0
    TI__Genius 12560 points

    Hi Amy,

    For multiple LMX2594 devices sync, they need to follow the flow chart mentioned in the datasheet (section 7.3.10.2).

    According to this, when the channel divider is greater than 512, it should go in category 4, which will not synchronize output. Same should follow for SYSREF divider also, where SYSREF divider value is 2560 for 3.90625MHz at RFoutB and it will not synchronize SYSREF outputs in Master SYSREF generation.

    In this case, SYSREF can operate in repeater mode and it should synchronize. To operate in repeater mode, SYSREF_REPEAT bit should go high R71[2] --> 1 along with SYSREF_EN and SYSREF input at SysRefReq pin.

    Try with SYSREF_repeater setting and it should provide output at RFoutB port.

    Meantime, if possible share the .tcs file of their setting to go over it.

    Regards,

    Ajeet Pal