CC1000
5. Circuit Description
RSSI/IF
MIXER
RF_IN
LNA
DEMOD
CONTROL
DIO
IF STAGE
DCLK
PDATA, PCLK, PALE
3
/N
PA
RF_OUT
BIAS
R_BIAS
XOSC_Q2
XOSC_Q1
CHARGE
PUMP
VCO
PD
/R
OSC
LPF
~
L1 L2
CHP_OUT
Figure 1. Simplified block diagram of the CC1000
In transmit mode the voltage controlled
oscillator (VCO) output signal is fed
directly to the power amplifier (PA). The
RF output is frequency shift keyed (FSK)
by the digital bit stream fed to the pin DIO.
The internal T/R switch circuitry makes the
antenna interface and matching very easy.
A simplified block diagram of CC1000 is
shown in Figure 1. Only signal pins are
shown.
In receive mode CC1000 is configured as a
traditional superheterodyne receiver. The
RF input signal is amplified by the low-
noise amplifier (LNA) and converted down
to the intermediate frequency (IF) by the
mixer (MIXER). In the intermediate
frequency stage (IF STAGE) this
downconverted signal is amplified and
filtered before being fed to the
demodulator (DEMOD). As an option a
RSSI signal, or the IF signal after the
mixer is available at the RSSI/IF pin. After
demodulation CC1000 outputs the digital
demodulated data on the pin DIO.
Synchronisation is done on-chip providing
data clock at DCLK.
The frequency synthesiser generates the
local oscillator signal which is fed to the
MIXER in receive mode and to the PA in
transmit mode. The frequency synthesiser
consists of a crystal oscillator (XOSC),
phase detector (PD), charge pump
(CHARGE PUMP), VCO, and frequency
dividers (/R and /N). An external crystal
must be connected to XOSC, and only an
external inductor is required for the VCO.
The 3-wire digital serial interface
(CONTROL) is used for configuration.
SWRS048A
Page 9 of 55
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