TDA7461NDTR STMicroelectronics, TDA7461NDTR Datasheet - Page 26

• Manufacturer Part Number: TDA7461NDTR
• Description: IC PROCESSOR CAR RAD SGNL SO-28
• Manufacturer: STMicroelectronics
• Type: Car Signal Processorr

Specifications of TDA7461NDTR

• Applications: Automotive Systems
• Mounting Type: Surface Mount
• Package / Case: 28-SOIC (7.5mm Width)
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Stereo decoder part
4.5
Figure 20. Block diagram of the stereo decoder
4.5.1
4.5.2
26/48
MPX
100K
Description of stereo decoder
The stereo decoder part of the TDA7461 (see
demodulate the MPX signal like pilot tone dependent mono/stereo switching as well as
“stereo blend” and “high cut” functions. Adaptations like programmable input gain, roll-off
compensation, selectable de-emphasis time constant and a programmable fieldstrength
input allow to use different IF devices.
Stereo decoder mute
The TDA7461 has a fast and easy to control RDS mute function which is a combination of
the audioprocessor softmute and the high-ohmic mute of the stereo decoder. If the stereo
decoder is selected and a softmute command is sent (or activated through the SM pin) the
stereo decoder will be set automatically to the high-ohmic mute condition after the audio
signal has been soft muted.
Hence a checking of alternate frequencies could be performed. To release the system from
the mute condition simply the unmute command must be sent: the stereo decoder is
unmuted immediately and the audioprocessor is softly unmuted.
signal V
the stereo decoder mute can be switched off by setting bit 3 of the Softmute byte to "0". A
stereo decoder mute command (bit 0, stereo decoder byte set to "1") will set the stereo
decoder in any case independently to the high-ohmic mute state.
If any other source than the stereo decoder is selected the decoder remains muted and the
MPX pin is connected to Vref to avoid any discharge of the coupling capacitor through
leakage currents.
Input stages
The In gain stage allows to adjust the MPX signal to a magnitude of about 1Vrms internally
which is the recommended value. The 4
and is used to attenuate spikes and noise and acts as an anti aliasing filter for the following
switch capacitor filters.
3.5 ... 11dB
STEP 2.5dB
INGAIN
O
as well as the internal stereo decoder mute signal. This influence of Softmute on
NOISE BLANKER
LP 80KHz
4.th ORDER
PILOT-DET.
INFILTER
D97AU762
PLL +
STEREO
HOLDN
F19
F38
- PLOT CANC
- ROLL-OFF COMP.
- LP 25KHz
DEMODULATOR
th
order input filter has a corner frequency of 80 kHz
Figure
SB CONTROL
-
20) contains all functions necessary to
MPINFL
LEVEL INTERN
MULTIPATH
DETECTOR
REF 5V
VSBL
t=50 or 75μs
DEEMPHASIS
+ HIGHCUT
Figure 21
CONTROL
D
HC
A
LP 2.2KHZ
1.th ORDER
GAIN 0..10dB
LEVEL INPUT
shows the output
FM_L
FM_R
VHCCH
VHCCL
TDA7461
LEVEL
MPIN
MPOUT