Texas Instruments CC112 Series, User Manual, Page: 65 / 109

CC112X/CC1175
SWRU295C Page 65 of 108
The LO divider/band select decoding is shown in Table 29.
FS_CFG.FSD_BANDSELECT
LO Divider RF Band [MHz]
0000 - 0001 - Not in use
0010 4 820 - 960
0011 - Not in use
0100 8 410 - 480
0101 - Not in use
0110 12 273.3 - 320
0111 - Not in use
1000 16 205 - 240
1001 - Not in use
1010 20 164 - 192
1011 24 136.7 - 160
1100 - 1111 - Not in use
Table 29: RF Band Selection Decoding
Since the RF band is determined by the LO divider setting, the different RF bands will also have
different frequency resolution. Note that the frequency offset word is related to the VCO frequency
programming, and hence any crystal inaccuracy compensation is therefore independent of the
selected RF band.
See Table 30 for an overview of the RF resolution.
RF Programming Resolution [Hz]
RF Band [MHz] XOSC @ 32 MHz XOSC @ 40 MHz
820 - 960 30.5 38.1
410 - 480 15.3 19.1
273.3 - 320 10.2 12.7
205 - 240 7.6 9.5
164 - 192 6.1 7.6
136.7 - 160 5.1 6.4
Table 30: RF Programming Resolution
8.13 IF Programming
The IF frequency is given by Equation 25 below (
FREQ_IF
is found in the
FREQ_IF_CFG
register).
XOSC IF
f
IF FREQ
f
15
2
_
Equation 25: IF Frequency
Note that
FREQ_IF
is given in two‟s complement format, hence both positive and negative IF are
supported.
8.14 FS Calibration
The internal on-chip FS characteristics will vary with temperature and supply voltage changes as well
as the desired operating frequency. In order to ensure reliable operation,
CC112X
includes frequency
synthesizer self-calibration circuitry. This calibration should be done regularly, and must be performed
after turning on power and before using a new radio frequency.