RF2489PCBA-41X View Datasheet(PDF) - RF Micro Devices
Part Name
Description
MFG CO.
'RF2489PCBA-41X' PDF : 30 Pages View PDF
RF2489
Application Schematic with Dual-Band TX LO Buffer Output
VCC
BAND SEL
33 nF
DNI
IP SET
IF SEL
VCC
L2
C1
47 nH
33 nF
20 kΩ
5.1 kΩ
VCC
8.7 nH
F2
6 GND GND 4
3 GND GND 1
DNI
FM IF OUT
VCC
CDMA
IF OUT
/2 SELECT
LO IN
HB/LB LO OUT
C2
DNI
C2
DNI
68 Ω
2 nH
0Ω
L1
R
C1
C1
L2
0Ω
L1
R
C1
32
31
30
29
28
27
26
25
1
2
3
4
/2
5
6
7
8
9
10
11
12
24
23
S 1.5 nH
22
47 nH
33 nF
N 21
33 nF
33 nF
20
IG 1pF
19
7.5 nH
18
S17
DE 13
14
15
16
7.5 nH
15 nH
0Ω
0.5 pF
1 nH
DNI
LNA L IN
LNA H IN
VCC
VCC
TX BUFF ENABLE
BUF ENABLE
W47 nH
NE 33nF
F1
DNI
5 OUT
IN 2
LNA GAIN
MIX GAIN
Output Interface Network
R L1, C1, and R form a current combiner which per-
forms a differential to single-ended conversion at the
O IF frequency and sets the output impedance. In most
where ROUT is the desired output impedance and RP is
the parasitic equivalent parallel resistance of L1.
F cases, the resonance frequency is independent of R
C1 should be chosen as high as possible (not greater
and can be set according to the following equation:
than 22pF), while maintaining an RP of L1 that allows
TfIF =
O 2π
1
L21(C1 + CEQ)
for the desired ROUT.
L2 and C2 serve dual purposes. L2 serves as an output
N bias choke, and C2 serves as a series DC block.
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.
In addition, L2 and C2 may be chosen to form an imped-
ance matching network if the input impedance of the IF
filter is not equal to ROUT. Otherwise, L2 is chosen to be
R can then be used to set the output impedance
according to the following equation:
( ) R =
4
1
ROUT
-
1
RP
-1
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 A21 DS070308
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.
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