C2510Fx / CC2511Fx
9.2 Radio
requiring very few external components. See
Section 14 for details.
CC2510Fx/CC2511Fx features an RF transceiver
based on the industry-leading CC2500,
10 Application Circuit
Only a few external components are required
for using the CC2510Fx/CC2511Fx. The
recommended application circuit for CC2510Fx
is shown in Figure 10. The recommended
application circuits for CC2511Fx are shown in
Figure 11 and Figure 12. The first of the
recommended CC2511Fx circuit uses
a
fundamental crystal and the second uses a 3rd
overtone crystal. The external components are
described in Table 28, and typical values are
given inTable 29.
10.1 Bias Resistor
The bias resistor R271 is used to set an
accurate bias current.
10.2 Balun and RF Matching
The balanced RF input and output of
CC2510Fx/CC2511Fx share two common pins and
are designed for a simple, low-cost matching
and balun network on the printed circuit board.
The RX- and TX switching at the
CC2510Fx/CC2511Fx front-end is controlled by a
dedicated on-chip function, eliminating the
need for an external RX/TX-switch.
C232, C242, and two inductive transmission
PCB lines form the recommended balun that
converts the differential RF port on CC2510Fx to
a single-ended RF signal. For the CC2511Fx
balun, the inductive PCB lines are replaced by
L241 and L231. Note that either of the
solutions (PCB lines or discrete components)
can be used for both the chips. C241 and
C231 are needed for DC blocking. Together
with an appropriate LC filter network, the balun
components also transform the impedance to
match a 50 Ω antenna (or cable). Component
values for the RF balun and LC network are
found in the latest CC2510EM and
CC2511Dongle reference designs ([1] and [2]).
Suggested values are also listed in Table 29.
The balun and LC filter component values,
their placement and layout are important in
order to keep the performance of the
CC2510Fx/CC2511Fx optimized. It is highly
recommended to follow the CC2510EM /
CC2511Dongle reference designs. Gerber
files for the reference designs are available for
download from the TI website
A few passive external components combined
with the internal RX/TX switch/termination
circuitry ensures match in both RX and TX
mode.
Although CC2510Fx/CC2511Fx has a balanced
RF input/output, the chip can be connected to
a single-ended antenna with few external low
cost capacitors and inductors.
The
passive
matching/filtering
network
connected to CC2510Fx/CC2511Fx should have
the following differential impedance as seen
from the RF-port (RF_P and RF_N) towards
the antenna:
Zout = 80 + j74 Ω
SWRS055D
Page 33 of 243
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