EVAL-ADF7021DBZ5 Datasheet, PDF (57/64 Pages) Analog Devices – High Performance Narrow-Band Transceiver IC

Data Sheet
REGISTER 10—AFC REGISTER
MAX_AFC_RANGE
KP
KI
AFC SCALING_FACTOR
ADF7021
ADDRESS
BITS
KP3 KP2 KP1 KP
0 0 0 2^0
0 0 1 2^1
.
.
.
...
1 1 1 2^7
KI4 KI3 KI2 KI1 KI
0 0 0 0 2^0
0 0 0 1 2^1
.
.
.
.
...
1 1 1 1 2^15
AE1 AFC ENABLE
0 OFF
1 AFC ON
MA8 ...
0
...
0
...
0
...
0
...
.
...
.
...
.
...
1
...
1
...
1
...
MAX AFC
MA3 MA2 MA1 RANGE
0011
0102
0113
1004
.
.
.
.
.
.
.
.
.
.
.
.
1 0 1 253
1 1 0 254
1 1 1 255
M12 ...
0
...
0
...
0
...
0
...
.
...
.
...
.
...
1
...
1
...
1
...
AFC SCALING
M3 M2 M1 FACTOR
0011
0102
0113
1004
.
.
.
.
.
.
.
.
.
.
.
.
1 0 1 4093
1 1 0 4094
1 1 1 4095
Figure 72. Register 10—AFC Register Map
The AFC_SCALING_FACTOR can be expressed as
AFC
_
SCALING
_
FACTOR
=
Round

2
24 _{× 500}
XTAL

The settings for KI and KP affect the AFC settling time and
AFC accuracy. The allowable range of each parameter is
KI > 6 and KP < 7
The recommended settings to give optimal AFC performance
are KI = 11 and KP = 4.
To tradeoff between AFC settling time and AFC accuracy, the
KI and KP parameters can be adjusted from the recommended
settings (staying within the allowable range) such that
AFC Correction Range = MAX_AFC_RANGE × 500 Hz
When the RF_DIVIDE_BY_2 (R1_DB18) is enabled, the
programmed AFC correction range is halved. The user
accounts for this halving by doubling the programmed
MAX_AFC_RANGE value.
Signals that are within the AFC pull-in range but outside the IF
filter bandwidth are attenuated by the IF filter. As a result, the
signal can be below the sensitivity point of the receiver and,
therefore, not detectable by the AFC.
Rev. B | Page 57 of 64