TRF2050

SLWS030E– JUNE 1996 – REVISED OCTOBER 2000

23

POST OFFICE BOX 655303

For contiguous channels, the following rules must be observed:

For PR = 01: 61

≤ NM1 ≤ 4095 and 0 ≤ NM2 ≤ 63, which yields minimum and maximum divide ratios of 4032

and 266303, respectively.

For PR = 10: 14

≤ NM1 ≤ 4095 and 0 ≤ NM2 ≤ 15, and 0 ≤ NM3 ≤ 15, which yields minimum and maximum

divide ratios of 1096 and 264335, respectively.

The A-Word is loaded only when a main divider synchronization signal is active. This prevents phase jumps

when reprogramming the main divider. The synchronization signal is generated by the main divider, and it is

active while the main divider is counting down from the programmed value. When the main divider reaches its

terminal count, a main divider output pulse is sent to the main phase detector. Also at this time, the loading of

the A-Word is disabled. Therefore, to correctly load the new A-Word, the STROBE signal must be active high

for at least a minimum number of VCO input cycles at RFIN.

The TRF2050 main synthesizer loop can operate as a traditional integer-N feedback PLL or as a fractional-N

feedback PLL. The integer-N feedback loop divides the VCO frequency by integer values of N, which results

in phase detector reference comparisons at the desired channel spacing. A fractional-N feedback loop divides

the VCO frequency by an integer term plus a fractional term, which results in phase detector reference

comparisons at integer multiples of the desired system channel spacing.

Integer-N division: VCO frequency