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ADF 4350 MOD Vs Fract

Question asked by grb on Nov 18, 2010
Latest reply on Nov 18, 2010 by grb


When I use the EVAL ADF4350 program it almost automatically sets the registers for minimum MOD value in Register 1 and the corresponding Int and Fract values in Register 0. Mathematically I can get the same frequency output by keeping the MOD value constant and varying Fract.

For example, if I want to get 2351.3 MHz, Eval can only set MOD=100 and Fract=13. 13 being an odd number and a prime number.

However, if I want 2351.2, while MOD=100 and Fract=12 would seem logical, EVAL program choses MOD=25 and Fract=3 or it can actually choose MOD=50, Fract=6 also.

Are there phase noise or spurious output related issues associated with these choices. Logically it would seem if MOD=100 gives a particular spur performance, it will be consistent with frequencies no matter what the Fract/MOD.