CC2420 Chipcon AS, CC2420 Datasheet - Page 15

• Manufacturer Part Number: CC2420
• Description: 2.4 GHz RF Transceiver for IEEE 802.15.4 and ZigBee
• Manufacturer: Chipcon AS

Circuit Description
A simplified block diagram of
shown in Figure 2.
CC2420
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 ADCs.
gain control, final channel filtering, de-
spreading, symbol correlation and byte
synchronisation are performed digitally.
When the SFD pin goes high, this indicates
that a start of frame delimiter has been
detected.
in a 128 byte receive FIFO. The user may
read the FIFO through a SPI interface.
CRC is verified in hardware. RSSI and
correlation values are appended to the
frame. CCA is available on a pin in receive
mode. Serial (unbuffered) data modes are
also available for test purposes.
Chipcon AS SmartRF® CC2420 Preliminary Datasheet (rev 1.0), 2003-11-17
On-chip
BIAS
TX/RX CONTROL
CC2420
R
LNA
SmartRF
PA
features a low-IF receiver. The
CC2420
16 MHz
XOSC
Control
Power
®
buffers the received data
Σ
Figure 2.
CC2420
Automatic
CC2420
0
90
is
simplified block diagram
AUTOMATIC GAIN CONTROL
SmartRF
The
up-conversion. The data is buffered in a
128 byte transmit FIFO (separate from the
receive FIFO). The preamble and start of
frame
hardware. Each symbol (4 bits) is spread
using
sequence to 32 chips and output to the
digital-to-analog converters (DACs).
An analog lowpass filter passes the signal
to the quadrature (I and Q) upconversion
mixers. 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 very 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 RXTX_SWITCH to RF_P and
RF_N through an external DC path.
Optionally one output can be turned off,
giving a single ended output, but at the
TX POWER CONTROL
ADC
ADC
SYNTH
DAC
DAC
FREQ
CC2420
the
delimiter
transmitter is based on direct
IEEE
- Digital RSSI
- Gain Control
- Image Suppression
- Channel Filtering
- Demodulation
- Frame
- Data spreading
- Modulation
synchronization
DEMODULATOR
MODULATOR
DIGITAL
DIGITAL
ENCRYPTION
®
INTERFACE
WITH FIFO
BUFFERS,
CRC AND
DIGITAL
are
802.15.4
CC2420
generated
Analog test
Digital and
regulator
interface
voltage
Page 15 of 85
Serial
spreading
by