RF2489 Ver la hoja de datos (PDF) - RF Micro Devices
Número de pieza
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Lista de partido
RF2489 Datasheet PDF : 16 Pages
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Preliminary
RF2489
VCC
BAND SEL
IP SET
IF SEL
VCC
FM IF OUT
VCC
CDMA
IF OUT
/2 SELECT
LO IN
HB LO OUT
LB LO OUT
VCC
TX BUFF ENABLE
BUF ENABLE
Application Schematic
C2
DNI
C2
DNI
68 Ω
2 nH
2 nH
L2
C1
0Ω
L1
R
C1
C1
L2
0Ω
L1
R
C1
33 nF
DNI
47 nH
33 nF
20 kΩ
5.1 kΩ
32
31
30
29
28
27
26
25
1
24
VCC
8.7 nH
F2
6 GND GND 4
3 GND GND 1
DNI
2
3
4
/2
5
6
23
1.5 nH
22
47 nH
33 nF
21
33 nF
33 nF
20
1 pF
19
7.5 nH
7
18
8
9
17
10
11
12
13
14
15
16
7.5 nH
15 nH
0Ω
0.5 pF
1 nH
DNI
47 nH
33 nF
F1
DNI
5 OUT
IN 2
LNA L IN
LNA H IN
VCC
8
LNA GAIN
MIX GAIN
Output Interface Network
L1, C1, and R form a current combiner which per-
forms a differential to single-ended conversion at the
IF frequency and sets the output impedance. In most
cases, the resonance frequency is independent of R
and can be set according to the following equation:
fIF =
2π
1
L21(C1 + CEQ)
Where CEQ is the equivalent stray capacitance and
capacitance looking into pins 1 and 2. An average
value to use for CEQ is 2.5pF to 3pF.
R can then be used to set the output impedance
according to the following equation:
( ) R =
4
1
ROUT
-
1
RP
-1
where ROUT is the desired output impedance and RP
is the parasitic equivalent parallel resistance of L1.
C1 should be chosen as high as possible (not greater
than 22pF), while maintaining an RP of L1 that allows
for the desired ROUT.
L2 and C2 serve dual purposes. L2 serves as an out-
put bias choke, and C2 serves as a series DC block.
In addition, L2 and C2 may be chosen to form an
impedance matching network if the input impedance
of the IF filter is not equal to ROUT. Otherwise, L2 is
chosen to be large, and C2 is chosen to be large if a
DC path to ground is present in the IF filter, or omitted
if the filter is DC blocked.
Rev A10 011017
8-43
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