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MAX2871 Phase Control Help

Category: Software
Product Number: MAX2871

The MAX2871 PLL datasheet is lacking information on how to actually change the phase of the output signal. The Dev kit software does things not explained clearly in the datasheet. Register 3 CDM[1:0] is never explained, what is Phase adjustment mode and how is it used? My firmware mimics the functionality of the dev kit but I get no results.

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  • Yes, we have tried this many times using the P value in REG1 and using the CDM bits in reg 3. We are in fractional mode and do not have Reg5 bit 24 set to 1. The best results we have seen is a single phase shift increment on the first toggle of CDM bit 1, but no following phase increments will occur. Oddly the older MAX2870 does seem to work.

  • I had a look at the MAX2870 datasheet and it says that you need to enable the phase change by setting CDM = 10, followed by a reset of CDM = 00 ("Phase Shift Mode" section on page 16). If you say this is working for you on MAX2870 but not MAX2871, then I don't know what the solution is. Best to request technical support at the link I posted earlier so that the correct support person is assigned to your query.

    If you do find a solution, please come back and update us here. Thanks.