
Programming Description (Continued)
RF N Counter Setting:
Counter Name
Symbol
Function
Modulus Counter
RF_FN
RF N Divider
N = Prescaler x RF_B + RF_A + (RF_FN / f
OSC)10
4
Programmable
Counter
RF_B
Swallow Counter
RF_A
Pulse Swallow Function:
f = {Prescaler x RF_B + RF_A + (RF_FN / f
OSC)x10
4}xf
OSC where (RF_A < RF_B)
where
f
VCO: Output frequency of voltage controlled oscillator (VCO)
Prescaler Values:
Device Type
RF Prescaler
GPS Prescaler
LMX2522
8
6
LMX2532
6
8
RF_B: Preset divide ratio of binary 4-bit programmable counter (2
≤ RF_B ≤ 15)
RF_A: Preset divide ratio of binary 3-bit swallow counter (0
≤ RF_A ≤ 7 for prescaler of 8 or 0 ≤ RF_A ≤ 5 for prescaler of 6)
RF_FN: Preset numerator of binary 11-bit modulus counter (0
≤ RF_FN < 1920 for f
OSC = 19.20 MHz; 0
≤ RF_FN < 1968 for f
OSC
= 19.68 MHz).
f
OSC: Reference oscillator frequency
NOTE: For the use of reference frequencies other than those specified, please contact National Semiconductor.
LMX2522/LMX2532
www.national.com
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