CC2400_08 Datasheet, PDF (15/84 Pages) Texas Instruments – 2.4 GHz Low-Power RF Transceiver

CC2400
15 Circuit Description
LNA
TX/RX CONTROL
SmartRF ^®
CC2400
Power
Control
PA
Σ
On-chip
BIAS
XOSC
0
90
ADC
ADC
DIGITAL
DEMODULATOR
- Digital RSSI
- Gain Control
- Image Suppression
- Channel Filtering
- Demodulation
AGC CONTROL
FREQ
SYNTH
TX POWER CONTROL
DIGITAL
INTERFACE /
FIFO
DAC
DAC
DIGITAL
MODULATOR
- Data Filtering
- Modulation
- Power Control
16 MHz
Figure 2. CC2400 simplified block diagram
A simplified block diagram of CC2400 is
shown in Figure 2.
CC2400 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 (1 MHz), the I/Q
signal is filtered and amplified, and then
digitized by the ADCs. Automatic gain
control, final channel filtering,
demodulation and bit synchronization is
performed digitally.
CC2400 outputs (in un-buffered mode only)
the digital demodulated data on the DIO
pin. A synchronized data clock is then
available at the DCLK pin. In buffered
mode the demodulated data is sent to a
FIFO and is accessible through the SPI
interface. RSSI is available in digital
format and can be read via the serial
interface. The RSSI also features a
programmable carrier sense indicator with
output on either GIO1 or GIO6.
In transmit mode the baseband signal is
directly up-converted quadrature (I and Q)
and then fed to the power amplifier (PA).
The TX IF signal is frequency shift keyed
(FSK). Optionally Gaussian filtering can be
used enabling GFSK. The BT of the
Gaussian filter is 0.5 for a datarate of
1 Mbps.
The internal T/R switch circuitry simplifies
the antenna interface and matching. The
antenna connection is differential. 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
SWRS042A
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