CC2500
SWRS040C
Page 18 of 89
balun that converts the differential RF signal
on
CC2500
to a single-ended RF signal. C121
and C131 are needed for DC blocking.
Together with an appropriate LC network, the
balun
components
also
transform
the
impedance to match a 50
antenna (or
cable). Suggested values are listed in Table
15.
The balun and LC filter component values and
their placement are important to keep the
performance
optimized.
It
is
highly
recommended
to
follow
the
CC2500EM
reference design ([4]).
Crystal
The crystal oscillator uses an external crystal
with two loading capacitors (C81 and C101).
See Section 26 on page 50 for details.
Power Supply Decoupling
The power supply must be properly decoupled
close to the supply pins. Note that decoupling
capacitors are not shown in the application
circuit. The placement and the size of the
decoupling capacitors are very important to
achieve
the
optimum
performance.
The
CC2500EM reference design ([4]) should be
followed closely.
Component
Description
C51
Decoupling capacitor for on-chip voltage regulator to digital part
C81/C101
Crystal loading capacitors, see Section 26 on page 50 for details
C121/C131
RF balun DC blocking capacitors
C122/C132
RF balun/matching capacitors
C123/C124
RF LC filter/matching capacitors
L121/L131
RF balun/matching inductors (inexpensive multi-layer type)
L122
RF LC filter inductor (inexpensive multi-layer type)
R171
Resistor for internal bias current reference
XTAL
26-27 MHz crystal, see Section 26 on page 50 for details
Table 14: Overview of External Components (excluding supply decoupling capacitors)
Antenna
(50 Ohm)
D
ig
it
a
l
In
te
fa
c
e
1.8V-3.6V power supply
6
G
D
O
0
7
C
S
n
8
X
O
S
C
_
Q
1
9
A
V
D
D
1
0
X
O
S
C
_
Q
2
S
I
2
0
G
N
D
1
9
D
G
U
A
R
D
1
8
R
B
IA
S
1
7
G
N
D
1
6
1 SCLK
2 SO (GDO1)
3 GDO2
4 DVDD
5 DCOUPL
AVDD 15
AVDD 14
RF_N 13
RF_P 12
AVDD 11
XTAL
C122
C132
L131
L121
L122
C123
C124
R171
C81
C101
C51
CSn
GDO0
(optional)
GDO2
(optional)
SO
(GDO1)
SCLK
SI
CC2500
DIE ATTACH PAD:
C131
C121
Alternative:
Folded dipole PCB
antenna (no external
components needed)
Figure 3: Typical Application and Evaluation Circuit (excluding supply decoupling capacitors)
Содержание CC2500
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