Philips Semiconductors
Product specification
New In Car Entertainment car radio tuner IC with
Precision Adjacent Channel Suppression (NICE-PACS)
TEA6848H
7
FUNCTIONAL DESCRIPTION
Oscillators
7.3
FM signal channel
7.1
7.3.1
FM MIXER 1
7.1.1
VCO
FM quadrature mixer converts FM RF (65 to 108 MHz and
weather band) to IF of 10.7 MHz. The FM mixer provides
inherent image rejection and high RF sensitivity.
The varactor tuned VCO provides the local oscillator signal
for both FM and AM mixer 1. It has a frequency range of
162.9 to 248.2 MHz.
It is capable of tuning the US FM, US weather,
Europe FM, Japan FM and East Europe FM bands:
7.1.2
PLL
• US FM = 87.9 to 107.9 MHz
Fast synthesizer PLL tuning system with local control for
inaudible RDS updating.
• US weather FM = 162.4 to 162.55 MHz
• Europe FM = 87.5 to 108 MHz
• Japan FM = 76 to 91 MHz
7.1.3
CRYSTAL OSCILLATOR
• East Europe FM = 65 to 74 MHz.
The crystal oscillator provides a 20.5 MHz signal that is
used for:
7.3.2
BUFFER OUTPUT FOR WEATHER BAND FLAG
(PIN WBFLAG)
• Reference frequency for frequency synthesizer PLL
• Local oscillator for AM mixer 2 and FM mixer 2
• Reference frequency for the IF counter
The buffer output on pin WBFLAG is HIGH for weather
band mode.
• Timing signal for the RDS update algorithm
7.3.3
FM KEYED AGC
• Reference frequency (75.368 kHz) for the TEA688x (car
audio signal processor - CASP) or TEF689x (car radio
integrated signal processor - CRISP).
The AGC threshold is programmable and the keyed AGC
function is switchable via the I2C-bus. AGC detection
occurs at the input of the first FM mixer. If the keyed AGC
function is activated, the AGC is keyed only by the narrow
band level. The AGC PIN diode drive can be activated via
the I2C-bus as a local function for search tuning. The AGC
sources a constant 10 mA current into the FM PIN diode in
AM mode.
7.2
DAA
To reduce the number of manual alignments in production
the following I2C-bus controlled Digital Auto Alignment
(DAA) functions are included:
• FM RF DAA
7.3.4
FM IF AMPLIFIER
– 7-bit DAA circuitry for the conversion of the VCO
tuning voltage to a controlled alignment voltage for
the FM antenna tank circuit
The FM IF amplifier provides 18 dB amplification with high
linearity over a wide dynamic range.
• FM and AM level DAA
7.3.5
FM MIXER 2
– Level DAA circuitry for alignment of slope (3-bit) and
starting point (5-bit) of the level curve
The FM mixer 2 converts 10.7 MHz FM IF1 to 450 kHz
FM IF2 in I and Q phase to achieve image rejection in the
demodulator.
• IF2 centre DAA
– Centre frequency alignment (7-bit) of integrated
FM IF2 dynamic selectivity.
2004 Nov 12
9
NXP [ NXP ]
