tda5225 Infineon Technologies Corporation, tda5225 Datasheet - Page 17

• Manufacturer Part Number: tda5225
• Description: Enhanced Sensitivity Multi-channel Quad-conf Igurat Ion Receiver With Digital Slicer
• Manufacturer: Infineon Technologies Corporation

2.4.2
The TDA5225 is separated into the following main blocks:
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2.4.3
The receiver path uses a double down conversion super-heterodyne/low-IF architecture,
where the first IF frequency is located around 10.7 MHz and the second IF frequency
around 274 kHz. For the first IF frequency an adjustment-free image frequency rejection
is realized by means of two low-side injected I/Q-mixers followed by a second order
passive polyphase filter centered at 10.7 MHz (PPF). The I/Q-oscillator signals for the
first down conversion are delivered from the PLL synthesizer. The frequency selection
in the first IF domain is done by an external CER filter (optionally by two, decoupled by
a buffer amplifier). For moderate or low cost applications, this ceramic filter can be
substituted by a simple LC Pi-filter or completely by-passed using the receiver as a
single down conversion low-IF scheme with 274 kHz IF frequency. The down conversion
to the second IF frequency is done by means of two high-side injected I/Q-mixers
together with an on-chip third order bandpass polyphase filter (PPF2 + BPF). The I/Q-
oscillator signals for the second down conversion are directly derived by division of two
from the crystal oscillator frequency. The bandwidth of the bandpass filter (BPF) can be
selected from 50 kHz to 300 kHz in 5 steps. For a frequency offset of -150 kHz to -120
kHz, the AFC (Automatic Frequency Control) function is mandatory. Activated AFC
option might require a longer preamble sequence in the receive data stream.
The receiver enable signal (RX_RUN) can be offered at each of the port pins to control
external components. Whenever the receiver is active, the RX_RUN output signal is
active. Active high or active low is configurable via PPCFG2 register.
Data Sheet
RF / IF Receiver
Crystal Oscillator and Clock Divider
Sigma-Delta Fractional-N PLL Synthesizer
ASK / FSK Demodulator incl. AFC, AGC and ADC
RSSI Peak Detector
Digital Baseband Receiver
Power Supply Circuitry
System Interface
System Management Unit
Block Overview
RF/IF Receiver
17
Functional Description
V1.0, 2010-02-19
TDA5225