Philips Semiconductors
Product specification
New In Car Entertainment (NICE) car radio
TEA6845AH; TEA6845H
7
FUNCTIONAL DESCRIPTION
Oscillators
It includes an AGC PIN diode drive circuit for the FM RF
AGC. The PIN diode drive can be activated via the I2C-bus
as a local or distance function.
7.1
7.1.1
VCO
The AGC threshold is programmable and the keyed AGC
function is switchable via the I2C-bus.
The L and C tuned VCO provides the local oscillator signal
for both FM and AM mixer 1. It has a frequency range of
151.2 to 248.2 MHz.
7.2.4
FM IF AMPLIFIERS
The two FM IF amplifiers provide 10 dB and 4 dB
amplification with high linearity and dynamic range.
7.1.2
CRYSTAL OSCILLATOR
The crystal oscillator provides a 20.5 MHz signal that is
used for:
7.2.5
FM DEMODULATOR
• Reference frequency for frequency synthesizer PLL
• Local oscillator for AM mixer 2
The FM quadrature demodulator includes automatic
centre frequency adjustment and THD compensation.
• Reference frequency for the IF counter
• Timing signal for the RDS update algorithm
7.3
AM signal channel
7.3.1
AM TUNER INCLUDING MIXER 1 AND MIXER 2
• Reference frequency (75.4 kHz) for the TEA6880H (car
audio signal processor - CASP) or TEF6890H (car radio
integrated signal processor).
The AM tuner is realized in a double conversion technique
and is capable of selecting LW, MW and SW bands.
AM mixer 1 converts AM RF to IF1 of 10.7 MHz, while
AM mixer 2 converts IF1 of 10.7 MHz to IF2 of 450 kHz:
7.1.3
PLL
Fast synthesizer PLL tuning system with local control for
inaudible RDS updating.
• LW = 144 to 288 kHz
• MW = 530 to 1710 kHz (US AM band)
• SW = 5.85 to 9.99 MHz (including the 31 m, 41 m and
7.2
FM signal channel
49 m bands).
7.2.1
DAA
7.3.2
AM RF AGC AND IF2 AGC
FM RF Digital Auto Alignment (DAA) circuitry for the
conversion of the VCO tuning voltage to a controlled
alignment voltage for the FM antenna tank circuit.
The AM RF includes a PIN diode drive circuit. The
threshold detection points for AM AGC are performed at
AM mixer 1 and AM IF2. AGC thresholds are
programmable via the I2C-bus.
7.2.2
FM I/Q MIXER
FM quadrature mixer converts FM RF (65 to 162.55 MHz)
to IF of 10.7 MHz. The FM mixer provides inherent image
rejection and high RF sensitivity.
7.3.3
AM DETECTOR
The AM detector provides AM level information and
AM AF or AM IF2.
It is capable of tuning the US FM, US weather,
Europe FM, Japan FM and East Europe FM bands:
7.3.4
AM AF OR IF2 SWITCH
• US FM = 87.9 to 107.9 MHz
The AM output provides either a detected AM AF or the
corresponding AM IF2 signal. The IF2 signal can be used
for AM stereo decoder processing.
• US weather FM = 162.4 to 162.55 MHz
• Europe FM = 87.5 to 108 MHz
• Japan FM = 76.0 to 91 MHz
• East Europe FM = 65.8 to 74 MHz.
7.2.3
FM KEYED AGC
FM contains keyed wide-band RF AGC. AGC detection
occurs at the FM mixer. The wide-band RF signal switches
a narrow band signal (IF) from the FM IF level detector
circuitry that controls the FM RF AGC block.
2001 Apr 12
9
NXP [ NXP ]
