Programming Information
57
3.5.18 Register 33h (67h), Loop Filter Bandwidth Resistor
This register is programmed based on the results of the loop bandwidth value
and the results of the loop capacitor selected in
Section 3.5.17
Register 38h
(71h), Loop Capacitor/Input Select on page 54
.
Figure 3.5.18: Register 33h Bit Assignments
Table 3.5.24: Loop Filter Resistor Register Definition
The following formulas and steps are used to calculate the Loop Resistor value:
1.
Calculate the value for R
in
:
(For the 4430-V) R
in
= ((5 x 10
-3
) x (Demod f
C
))/(LBW
2
x C)
(For the 4430-VN) R
in
= ((2.55 x 10
-5
) x (Demod f
C
))/(LBW
2
x C)
Where LBW is the loop bandwidth, Demod f
C
is the demodulator carrier fre-
quency and C is the loop capacitor value selected in
Section 3.5.17
Register 38h
(71h), Loop Capacitor/Input Select on page 54
.
2.
Calculate the value for R
3
and round to the nearest whole number.
R
3
= 1 x 10
6
/R
in
3.
Using
Figure 3.5.18
Register 33h Bit Assignments on page 57
determine the bit
or bit combinations that most closely approximate the value calculated for R
3
above.
7
6
5
4
3
2
1
0
0/1
0/1 0/1
0/1
0/1
0/1
0/1
-
Loop Filter Resistor [Bit weight = 1] LSB
Loop Filter Resistor [Bit weight = 3]
Loop Filter Resistor [Bit weight = 9]
Loop Filter Resistor [Bit weight = 27]
Loop Filter Resistor [Bit weight = 81]
Loop Filter Resistor [Bit weight = 243]
Loop Filter Resistor [Bit weight = 729] MSB
Unused
Bit No.
Bit Name(s)
Functional Description
07
Unused
Set to zero for proper operation
06-00
Loop Filter Resistor
(Set according to the formulas to follow)
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