LMX2320 National Semiconductor, LMX2320 Datasheet - Page 19

• Manufacturer Part Number: LMX2320
• Description: Frequency Synthesizer for RF Personal Communications
• Manufacturer: National Semiconductor

Application Information
Example
K
K
RF
F
N
ATTEN
if we choose R3
Converting to standard component values gives the follow-
ing filter values which are shown in Figure 4
Note 1 See related equation for K in Charge Pump Current Specification
VCO
ref
p
p
C1
R2
C2
R3
C3
e
opt
e
e
e
e
RF
e
e
e
e
e
43
e
2
e
2 8 mA (Note 1)
Definitions For this example V
be approximated using the curves in the Typical Performance Char-
acteristics for Charge Pump Current vs D
K are in mA You may also use K
case you must convert K
300 kHz
T1
T3
T2
C1
C2
R2
opt
e
560 pF
6 8 k
2700 pF
27 k
56 pF
34 MHz V
1665 MHz
c
12 dB
e
e
e
e
e
e
e
e
20 kHz
2
f
ref
sec
(9 682e4)
(3 462e
3 462e
2 437e
0 63 nF
0 63 nF
2 437e
3 88e
e
(2
10
e
5550
(12 20)
e
1
b
27k then C3
b
p
b
b
b
a
b
1 256e5
300e3)
tan
9
6
5
5
2
6
2 437e
3 402e
(3 462e
tan43 (3 862e
(3 462e
(9 682e4)
e
a
(2 8e
b
VCO
e
6 28 k
9 16e
1
2
3 462e
to (rad V) multiplying by 2
b
1
b
b
P
e
b
e
b
3) 34e6
5
6
tan43 (3 462e
b
6
e
9 16e
2
3 3V The value for K can then
6
b
a
e
7)
a
9 16e
b
1
5550
b
2
(2 8 mA 2
9 16e
27e3
6
9 16e
b
a
6
(Continued)
o
e
7
a
Voltage The units for
b
3 462e
3 88 nF
b
7
9 16e
b
7)
e
b
7)
1
rad) but in this
2
a
34 pF
b
6
e
a
b
a
6 9 16e
(9 682e4)
7)
2 437e
3 462e
9 16e
b
b
b
b
2
5
6 9 16e
7)
1
19
7)
(3 462e
a
2
(9 682e4)
b
b
6)
7
2
b
2
1
1
(2 437e
a
FIGURE 9 E 20 kHz Loop Filter
(9 682e4)
b
5)
2
2
(9 16e
b
7)
2
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