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Philips Semiconductors
Low-power FM stereo radio for
handheld applications
7
FUNCTIONAL DESCRIPTION
7.1
Low-noise RF amplifier
The LNA input impedance together with the LC RF input
circuit defines an FM band filter. The gain of the LNA is
controlled by the RF AGC circuit.
7.2
FM mixer
The FM quadrature mixer converts the FM RF
(76 MHz to 108 MHz) to an IF of 225 kHz.
7.3
VCO
The varactor tuned LC VCO provides the Local Oscillator
(LO) signal for the FM quadrature mixer. The VCO
frequency range is 150 MHz to 217 MHz.
7.4
Crystal oscillator
The crystal oscillator can operate with a 32.768 kHz clock
crystal or a 13 MHz crystal. The temperature drift of
standard 32.768 kHz clock crystals limits the operational
temperature range from −10 °C to +60 °C.
2004 Sep 13
CPOUT
1
2
VCOTANK1
VCOTANK2
3
4
V
CC(VCO)
TEA5768HL
DGND
5
V
6
CCD
7
DATA
CLOCK
8
Fig.2 Pin configuration.
24
LIMDEC2
23
LIMDEC1
22
TIFC
21
V
ref
20
MPXO
19
TMUTE
18
V
AFR
17
V
AFL
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The PLL synthesizer can be clocked externally with a
32.768 kHz, a 6.5 MHz or a 13 MHz signal via pin XTAL2.
The crystal oscillator generates the reference frequency
for:
• The reference frequency divider for the synthesizer PLL
• The timing for the IF counter
• The free-running frequency adjustment of the stereo
decoder VCO
• The centre frequency adjustment of the IF filters.
7.5
PLL tuning system
The PLL synthesizer tuning system is suitable to operate
with a 32.768 kHz or a 13 MHz reference frequency
generated by the crystal oscillator or applied to the IC from
an external source. The synthesizer can also be clocked
via pin XTAL2 at 6.5 MHz. The PLL tuning system can
perform an autonomous search tuning function.
7.6
RF AGC
The RF AGC prevents overloading and limits the amount
of intermodulation products created by strong adjacent
channels.
7
Product specification
TEA5768HL
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