TEA6849H Просмотр технического описания (PDF) - Philips Electronics

Номер в каталоге

Компоненты Описание

Список матч

TEA6849H

New In Car Entertainment car radio tuner IC with Precision Adjacent Channel Suppression (NICE-PACS)

Philips Electronics 

Philips Semiconductors

New In Car Entertainment car radio tuner IC with

Precision Adjacent Channel Suppression (NICE-PACS)

Product specification

TEA6849H

7.3.6 FM IF2 DYNAMIC SELECTIVITY

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.

7.3.7 FM QUADRATURE DEMODULATOR

The FM quadrature demodulator is adjustment free.

7.3.8 FM MPX SOFT MUTE

Muting depth and start of muting are adjustable via the

I2C-bus (see Figs 8 and 9).

7.3.9

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.

7.3.10 BANDWIDTH CONTROL ‘ACTIVE’ FLAG

(PIN IFBWFLAG)

Flag output IBFW = 1 from pin IFBWFLAG indicates that

the IF2 bandwidth is reduced.

7.3.11 BANDWIDTH CONTROL MONITOR VOLTAGE

(PIN VIFBW)

The actual bandwidth is indicated by a voltage at pin VIFBW

that is proportional, not linear, to the IF bandwidth.

7.4 AM signal channel

7.4.1 AM TUNER INCLUDING MIXER 1 AND MIXER 2

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:

• 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).

7.4.2 AM RF AGC

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.

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

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.

7.4.4 AM NOISE BLANKER

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.

Trigger sensitivity can be modified by adding an external

resistor at pin AMNBHOLD.

7.5 FM and AM level detector

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.

2003 Dec 19

10

Share Link: