W3000 Datasheet, PDF (8/28 Pages) Agere Systems – W3000 PLL Dual-Band Frequency Synthesizer

W3000 PLL Dual-Band Frequency Synthesizer
Advance Data Sheet
December 1999
PLL Programming Information
The oscillator frequency is selected according to the following expression:
where:
fVCO = ^{[(P * M) + A] * fREF}
R
fVCO
= VCO frequency
P/(P + 1) = Dual modulus prescaler
M
= Programmable counter ratio (2 to 2047), M > A
A
= Swallow counter ratio (0 to M – 1 or 127)
fREF
= External reference oscillator frequency
R
= Reference counter ratio (2 to 2047)
Example
You wish to have a VCO operating at 1172 MHz, ability to step the frequency in 200 kHz steps, and a reference
clock at 13 MHz.
Step 1:
Calculate the reference counter ratio R
R = ^{13 MHz} = 65
200 kHz
Step 2: Calculate M & A
fVCO = ^{[(P * M) + A]* fREF}
R
1172 = ^{[(64 * M) + A]* 13}
65
(64 * M + A) = ^{1172 * 65} = 5860
13
5860 _{= 9136}
64
64
M is an integer, and so is A; therefore, M = 91, and A = 36.
8
Lucent Technologies Inc.