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TEA6845AH

New In Car Entertainment (NICE) car radio

Philips Electronics 

Philips Semiconductors

New In Car Entertainment (NICE) car radio

Product specification

TEA6845AH; TEA6845H

7 FUNCTIONAL DESCRIPTION

7.1 Oscillators

7.1.1 VCO

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.

7.1.2 CRYSTAL OSCILLATOR

The crystal oscillator provides a 20.5 MHz signal that is

used for:

• Reference frequency for frequency synthesizer PLL

• Local oscillator for AM mixer 2

• Reference frequency for the IF counter

• Timing signal for the RDS update algorithm

• Reference frequency (75.4 kHz) for the TEA6880H (car

audio signal processor - CASP) or TEF6890H (car radio

integrated signal processor).

7.1.3 PLL

Fast synthesizer PLL tuning system with local control for

inaudible RDS updating.

7.2 FM signal channel

7.2.1 DAA

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.

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.

It is capable of tuning the US FM, US weather,

Europe FM, Japan FM and East Europe FM bands:

• US FM = 87.9 to 107.9 MHz

• 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.

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.

The AGC threshold is programmable and the keyed AGC

function is switchable via the I2C-bus.

7.2.4 FM IF AMPLIFIERS

The two FM IF amplifiers provide 10 dB and 4 dB

amplification with high linearity and dynamic range.

7.2.5 FM DEMODULATOR

The FM quadrature demodulator includes automatic

centre frequency adjustment and THD compensation.

7.3 AM signal channel

7.3.1 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 = 5.85 to 9.99 MHz (including the 31 m, 41 m and

49 m bands).

7.3.2 AM RF AGC AND IF2 AGC

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.

7.3.3 AM DETECTOR

The AM detector provides AM level information and

AM AF or AM IF2.

7.3.4 AM AF OR IF2 SWITCH

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.

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

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