CC2480_11 Datasheet, PDF (29/48 Pages) Texas Instruments – Z-Accel 2.4 GHz ZigBee Processor

CC2480
10 Radio
LNA
TXRX SWITCH
Power
Control
PA
Σ
0
90
AUTOMATIC GAIN CONTROL
ADC
ADC
DIGITAL
DEMODULATOR
- Digital RSSI
- Gain Control
- Image Suppression
- Channel Filtering
- Demodulation
- Frame
synchronization
FREQ
SYNTH
TX POWER CONTROL
FFCTRL
RADIO
REGISTER
BANK
Register bus
CSMA/CA
STROBE
PROCESSOR
SFR bus
DAC
DAC
DIGITAL
MODULATOR
- Data spreading
- Modulation
IRQ
HANDLING
Figure 9: CC2480 Radio Module
A simplified block diagram of the IEEE
802.15.4 compliant radio inside CC2480 is
shown in Figure 9. The radio core is based on
the industry leading CC2420 RF transceiver.
CC2480 features a low-IF receiver. The
received RF signal is amplified by the low-
noise amplifier (LNA) and down-converted in
quadrature (I and Q) to the intermediate
frequency (IF). At IF (2 MHz), the complex I/Q
signal is filtered and amplified, and then
digitized by the RF receiver ADCs.
The CC2480 transmitter is based on direct up-
conversion. The preamble and start of frame
delimiter are generated in hardware. Each
symbol (4 bits) is spread using the IEEE
802.15.4 spreading sequence to 32 chips and
output to the digital-to-analog converters
(DACs).
The RF signal is amplified in the power
amplifier (PA) and fed to the antenna.
The internal T/R switch circuitry makes the
antenna interface and matching easy. The RF
connection is differential. A balun may be used
for single-ended antennas. The biasing of the
PA and LNA is done by connecting
TXRX_SWITCH to RF_P and RF_N through an
external DC path.
The frequency synthesizer includes a
completely on-chip LC VCO and a 90 degrees
phase splitter for generating the I and Q LO
signals to the down-conversion mixers in
receive mode and up-conversion mixers in
transmit mode. The VCO operates in the
frequency range 4800 – 4966 MHz, and the
frequency is divided by two when split into I
and Q signals.
An analog low pass filter passes the signal to
the quadrature (I and Q) up-conversion mixers.
An on-chip voltage regulator delivers the
regulated 1.8 V supply voltage.
CC2480 Data Sheet SWRS074
Page 29 of 43