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LMX2572: max data rate when using phase adjustment feature

Hans
Genius 12865 points

Part Number: LMX2572

Hello Team,

can you confirm that I can achieve a maximum toggle rate of about 4.5MHz when using a 75MHz SPI clock? Can I do a 180° phase shift for a BPSK by using MASH_SEED (page 19, data sheet) only with SPI or also with external pins? 

Thanks and Best Regards,

Hans

  • 0
    TI__Guru** 120270 points

    Hi Hans,

    the MASH_SEED is 32-bit long, assuming you just need 16-bit, then you need to write one register for each phase change. 

    A register is 25-bit (24 + 1). if the SPI is 75MHz, writing one register takes 0.33333µs. 

    The period of 4.5MHz is 0.22222µs, which is shorter than the register write time. So, phase change at a rate of 4.5MHz does not seem possible.