TEF6700HL NXP Semiconductors, TEF6700HL Datasheet - Page 11

• Manufacturer Part Number: TEF6700HL
• Description: Car Radio Tuner Front-end For Digital If
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7.10
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 an IF1 of 10.7 MHz, while
AM mixer 2 converts IF1 of 10.7 MHz to IF2 of 450 kHz:
7.11
The AM wideband AGC in front of the AM mixer 1 is
realized first by a cascoded NPN transistor, which controls
the transconductance of the RF amplifier JFET with 10 dB
of AGC range. Second, an AM PIN diode stage with 30 dB
of 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 some conditions, noise behaviour will increase. In this
case pins VAMCAS and VAMCASFB have to be left
open-circuit. In FM mode, the cascode 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 RF AGC are at the AM
mixer 1 input (threshold programmable via the I
and the IF2 AGC input (fixed threshold).
2003 Oct 21
LW from 144 to 288 kHz
MW from 522 to 1710 kHz (US AM band)
SW from 5.73 to 9.99 MHz (including the 31 m, 41 m
and 49 m bands).
Car radio tuner front-end for digital IF
AM tuner including mixer 1 and mixer 2
AM RF AGC
2
C-bus)
11
7.12
The detection point for the AM noise blanker is the output
stage of AM mixer 1, while blanking is realized at the
output of mixer 2.
7.13
This is a linear AM IF2 AGC amplifier. The gain controlled
AM IF2 is output via the multiplexed FM IF/AM IF2 buffer
to a car IF DSP IC (e.g. SAA7724H).
7.14
This buffers and multiplexes AM IF2 and FM IF to pin
IFOUT.
7.15
The 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 I
7.16
The output (open-collector) sinks a current which in
AM mode is proportional to the voltage at pin TRFAMAGC
and in FM mode proportional to the RF level detector
voltage (pin TFMAGC) inside the FM AGC.
2
C-bus.
AM noise blanker
AM IF2 AGC
FM IF and AM IF2 buffer
FM and AM level detector
FM/AM RF AGC buffer
Product specification
TEF6700HL