TUA4401K Infineon Technologies Corporation, TUA4401K Datasheet - Page 22

• Manufacturer Part Number: TUA4401K
• Description: Fm Car Radio Ic With Pll
• Manufacturer: Infineon Technologies Corporation

Wireless Components
3.4 Circuit Description
The TUA 4401K is a one chip FM car radio system consisting of RF frontend,
gain adjustable IF amplifier, FM-IF limiter amplifier, demodulator, PLL synthe-
sizer, IF counter for STS and ADC’s for fieldstrength and multipath detector.
The serial bus is a I
1. FM frontend
2. FM IF amplifier
3. FM limiter and demodulator
4. Multipath detector
5. A/D converter for fieldstrength and multipath detector
6. IF counter and multipath/fieldstrength evaluation for STS
The frontend consists of a two pin varactor tuned oscillator, a double bal-
anced mixer and a prestage AGC control circuit. The mixer has an improved
intermodulation behaviour and converts the RF signal to the 10,7 MHz IF
range . Two inputs allow both symmetrical and unsymmetrical operation.
The integrated AGC stage for prestage control drives MOSFETS as well as
PIN diodes a with cur- rent driver. The AGC threshold can be set with a serial
bus controlled 2 Bit DAC. For background receiver application the oscillator
is able run at double frequency, a subsequent frequency divider by 2 is acti-
vated by serial bus to provide the correct mixer frequency.
After the mixer an IF amplifier is present for IF post amplification. Input and
output impedance are both 330 Ohms for matching with ceramic filters. For
adjusting the over all gain the IF amplifier gain can be adjusted with a serial
bus controlled 4 Bit DAC.
The FM IF amplifier includes a seven stage capacitive coupled limiter ampli-
fier and a fieldstrength generator with high linearity and increased dynamic
range. The coincidence demodulator has an additional AFC short loop cir-
cuit with integrated varactor diode in parallel to the external tank circuit to
improve the distortion bahaviour in case of detuning.
A wideband multipath detector with analog output is available.
The 7 bit A/D converter has two input channels and works as successive
approximation converter. The conversion time for both input signals is t = 32
via bus into two bytes with the read subaddress 82H. The input voltage
range for both channels is 0...VREFD5V.
FM center frequencies ar available in two ranges set by bit D7 in subaddress
05H. For D7=1 the range of centerfrequency is 20.800 MHz...22.3875 MHz
in 128 steps (12.5 kHz per step). For D7=0 the range of centerfrequency is
10.400 MHz...11.1937 MHz in 128 steps (6.25 kHz per step).
The gate time is adjustable in 8 steps from 320us...40.96ms and the toler-
ance of the accepted count value, the window is adjustable in 5 steps from
+/- (6.25kHz...100kHz) for D7=0 in sub-address 05H and
s. The 7-bit digital-words from both channels (14 bit) are read out together
2
C type.
3 - 14
Functional Description
Specification, 17.02.00
TUA 4401K