CC1110Fx / CC1111Fx
9.2 Radio
CC1110Fx/CC1111Fx features an RF transceiver
based on the industry-leading CC1101, requiring
very few external components. See Section 10
for details.
10 Application Circuit
Only a few external components are required
Figure 12. The recommended CC1111Fx circuit
uses a fundamental crystal. The external
components are described in Table 28, and
typical values are given in Table 29.
for
using
the
CC1110Fx/CC1111Fx.
The
recommended application circuit for CC1110Fx is
shown in Figure 10. The recommended
application circuits for CC1111Fx are shown in
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
CC1110Fx/CC1111Fx share two common pins and
are designed for a simple, low-cost matching
and balun network on the printed circuit board.
The receive- and transmit switching at the
CC1110Fx/CC1111Fx front-end is controlled by a
dedicated on-chip function, eliminating the
need for an external RX/TX-switch.
The
passive
matching/filtering
network
connected to CC1110Fx/CC1111Fx should have the
following differential impedance as seen from
the RF-port (RF_P and RF_N) towards the
antenna:
Z
Z
Z
out 315 MHz = 122 + j31 Ω
out 433 MHz = 116 + j41 Ω
out 868/915 MHz = 86.5 + j43 Ω
A few passive external components combined
with the internal RX/TX switch/termination
circuitry ensure match in both RX and TX
mode.
To ensure optimal matching of the
CC1110Fx/CC1111Fx differential output it is highly
recommended to follow the CC1110EM
reference designs [1] or the CC1111 USB-
Dongle Reference Design [4] as closely as
possible. Gerber files for the reference designs
are available for download from the TI website.
Although CC1110Fx/CC1111Fx has a balanced RF
input/output, the chip can be connected to a
single-ended antenna with few external low
cost capacitors and inductors.
10.3 Crystal
what the internal RC oscillator can provide.
When not using X2, P2_3 and P2_4 may be
used as general IO pins.
The crystal oscillator for the CC1110Fx uses an
external crystal X1, with two loading capacitors
(C201 and C211).
The loading capacitor values depend on the
total load capacitance, CL, specified for the
crystal. The total load capacitance seen
between the crystal terminals should equal CL
for the crystal to oscillate at the specified
frequency. For the CC1110Fx using the crystal
X1, the load capacitance CL is given as:
The crystal oscillator for the CC1111Fx uses an
external crystal X1, with two loading capacitors
(C203 and C214).
Note: The high speed crystal oscillator
must be stable (SLEEP.XOSC_STB=1)
before using the radio.
1
CL =
+ CParasitic
1
1
+
The recommended application circuits also
show the connections for an optional 32.768
kHz crystal oscillator with external crystal X2
and loading capacitors C181 and C171. This
crystal can be used by the Sleep Timer if more
accurate wake-up intervals are needed than
C211 C201
The parasitic capacitance is constituted by pin
input capacitance and PCB stray capacitance.
Total parasitic capacitance is typically 2.5 pF.
SWRS033E
Page 36 of 239
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