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2.3 The Calculations
Software Setup
The right side of the main control screen shows the system setup calculations.
• FREF is the reference oscillator frequency in MHz.
• Fref_Frac is not used.
• RDIV is the number the reference frequency is divided by to get Fpfd.
• NDIV is the number the output frequency is divided by to get Fpfd.
• A and B are the variables in the equation Fout = Fpfd (A+PB) as discussed in the prescalar section of
the controls. See Appendix A.
• Fout is the actual frequency out.
• Fvco 1x is the undivided frequency out of the VCO.
• Fvco DIV2 is the frequency out of the VCO divided by 2.
• Fvco DIV4 is the frequency out of the VCO divided by 4.
• Spur offset is the offset of the phase frequency detector spur.
• Icp (Rbias) is the actual current of the charge pump. Calculated from [Icp(4.75k)]/Rbias = Icp
actual
.
SLWU035A – February 2007 – Revised March 2007 TRF3761 EVM User's Guide 9
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