Philips Semiconductors
Product specification
New In Car Entertainment car radio tuner IC with
Precision Adjacent Channel Suppression (NICE-PACS)
TEA6848H
7.3.6
FM IF2 DYNAMIC SELECTIVITY
7.4.2
AM RF AGC
The IF bandwidth of the FM IF2 is automatically adjusted
depending on modulation and reception conditions. The
centre frequency of the selectivity is adjusted by a 7-bit
instruction via the I2C-bus. The dynamic selectivity mode
and three fixed bandwidths (60, 90 and 130 kHz) can be
selected via the I2C-bus. The IF2 bandwidth is set to
13 kHz in weather band mode.
The AM wideband AGC in front of the first AM mixer is
realized first by a cascaded NPN transistor, which controls
the transconductance of the RF amplifier JFET with 10 dB
of AGC range. Second, an AM PIN diode stage with
antenna type and frequency dependent AGC range is
available. The minimum JFET drain source voltage is
controlled by a DC feedback loop (pin VAMCASFB) in
order to limit the cascode AGC range to 10 dB. If the
cascode AGC is not required, a simple RF AGC loop is
possible by using only a PIN diode. In this event
pins VAMCASFB and VAMCAS have to be open-circuit.
In FM mode, the cascade switches off the JFET bias
current to reduce total power consumption. The PIN diode
is biased by 1 mA in FM mode.
7.3.7
FM QUADRATURE DEMODULATOR
The FM quadrature demodulator is adjustment free.
7.3.8
ADJACENT CHANNEL DETECTOR AND THRESHOLD
EXTENSION
In the event of breakthrough of a strong neighbouring
transmitter, the IF2 bandwidth is reduced dynamically.
At low RF input voltages and low modulation levels the IF2
bandwidth is reduced to achieve improved sensitivity by
demodulator threshold extension.
The AGC detection points for AM AGC are at the first AM
mixer input (threshold programmable via the I2C-bus) and
the IF2 AGC input (fixed threshold).
7.4.3
AM DETECTOR
7.3.9
BANDWIDTH CONTROL ‘ACTIVE’ FLAG
(PIN IFBWFLAG)
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. Soft mute function is
controlled by the I2C-bus in AM mono mode.
Flag output IBFW = 1 from pin IFBWFLAG indicates that
the IF2 bandwidth is reduced.
7.4.4
AM NOISE BLANKER
7.3.10 BANDWIDTH CONTROL MONITOR VOLTAGE
(PIN VIFBW
)
The detection point for the AM noise blanker is the output
stage of AM mixer 1, while blanking is realized at the
output of the mixer 2.
The actual bandwidth is indicated by a voltage at pin VIFBW
that is proportional, not linear, to the IF bandwidth.
Trigger sensitivity can be modified by adding an external
resistor at pin AMNBHOLD.
7.4
AM signal channel
7.4.1
AM TUNER INCLUDING MIXER 1 AND MIXER 2
7.5
FM and AM level detector
The AM tuner is realized in a double conversion technique
and is capable of selecting LW, MW and SW bands.
FM and AM level detectors provide the temperature
compensated output voltage. The starting points and
slopes of the level detector outputs are programmable via
the I2C-bus.
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:
• LW = 144 to 288 kHz
• MW = 530 to 1710 kHz (US AM band)
• SW = 5.73 to 9.99 MHz (including the 31 m, 41 m and
49 m bands).
2004 Nov 12
10
NXP [ NXP ]
