TDA5225 Datasheet, PDF (18/176 Pages) Infineon Technologies AG – Enhanced Sensitivity Multi-Channel Quad-Configuration Receiver

TDA5225
Functional Description
The frequency relations are calculated with the following formulas:
f_IF1 = 10.7MHz
f_IF2
=
f---_I--F---1
39
f_crystal = f_IF2 × 80
f_LO2
=
-f--^c--^r--^y---^s--^t--^a--^l
2
f_LO1 = f_crystal × NF_divider
I-Mix
RX
Input
LNA
Q-Mix
C ER -
Filter
IF1
10 .7 MHz
CER-
Filter IF1
10.7 MHz
optional
IF
Attenuation
adjust
VCO
:1/:2/:3
N
ΣΔ Modulator
Channel select
IQ Divider : 4
Multi Modulos
Divider : N_FN
Band select
Figure 3 Block Diagram RF Section
I-
Mix2
Q-
Mix2
IQ :2
RSSI Generator
LP
harm sup
LP
alias sup
digital
FSK Demod
RX
FSK Data
ASK /
RSSI
ADC
RX
ASK Data
Channel Filter
Bandwidth select
Divider
:N
AFC
Filter
PD
Loop
Filter
Crystal
oscil -
lator
LF select
Band select
Channel select
LF select
Channel Filter select
IF Attenuation adjust
RSSI Gain/ Offset adjust
Front end
control unit
The front end of the receiver comprises an LNA, an image reject mixer and a digitally
gain controlled buffer amplifier. This buffer amplifier allows the production spread of the
on-chip signal strip, of external matching circuitry and RF SAW and ceramic IF filters to
be trimmed. The second image reject mixer down converts the first IF to the second IF.
Data Sheet
18
V1.0, 2010-02-19