TEF6721HL NXP Semiconductors, TEF6721HL Datasheet - Page 9

• Manufacturer Part Number: TEF6721HL
• Description: Car Radio Tuner Front-end For Digital If
• Manufacturer: NXP Semiconductors

Philips Semiconductors
TEF6721HL_4
Product data sheet
7.7 FM keyed AGC
7.8 AM mixer
7.9 AM RF AGC
The AGC detects at the FM mixer input and the IF AGC amplifier input. The AGC
threshold for the FM mixer input is programmable via the I
exceeded, the AGC sources a current to an external PIN diode circuit, keeping the RF
signal level at the FM mixer input constant.
The keyed function shifts the threshold of the AGC if the in-band signal is small. This
reduces desensitization by other strong transmitters. The amount of threshold shift is
limited to 10 dB. The keyed function can be activated via the I
in-band level information delivered from IF DSP via pin KAGC.
The AGC can be activated via the I
search tuning. In AM mode the AGC can be activated to source a constant 10 mA current
into the FM PIN diode.
The AM mixer has a high dynamic range and converts AM RF to an IF frequency of
10.7 MHz.
The outputs of the AM and FM mixers can be separated to allow the use of different IF
filters for AM and FM modes.
resistor R1 between pins AMIFIN and IFAGCBIAS the input impedance of the IF AGC
amplifier is matched to the AM IF filter output impedance.
The input impedance of the AM IF filter is matched to 330
The AM wideband AGC in front of the AM mixer 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
Fig 4. Separate IF paths for AM and FM mode
8.5 V
Rev. 04 — 20 December 2005
22
22
nF
12
MIXER
AM
Figure 4
10
2
I/Q MIXER
C-bus to source a fixed current as a local function for
11
FM
shows this optional application. By adding the
TEF6721HL
9
7
L1
L2
22
nF
Car radio tuner front-end for digital IF
6
FM IF filter
R2
AGC
IF
R3
5
22
nF
AM IF filter
2
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
C-bus. When the threshold is
4
with R2 and R3.
2
R1
C-bus and is controlled by
mdb414
TEF6721HL
3
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