TDA7340G Datasheet, PDF (16/27 Pages) STMicroelectronics – AUDIO SIGNAL PROCESSOR

TDA7340G
VOLUME
MSB
LSB
D7 D6 D5 D4 D3 D2 D1 D0
FUNCTION
0.31dB FINE ATTENUATION STEPS
0
00
0
1 -0.31dB
1
0 -0.62dB
1
1 -0.94dB
1.25dB COARSE ATTENUATION STEPS
0
0
0
0dB
0
0
1
-1.25dB
0
1
0
-2.5dB
0
1
1
-3.75dB
1
0
0
-5dB
1
0
1
-6.25dB
1
1
0
-7.5dB
1
1
1
-8.75dB
10dB GAIN ATTENUATION STEPS
0
0
0
20dB
0
0
1
10dB
0
1
0
0dB
0
1
1
-10dB
1
0
0
-20dB
1
0
1
-30dB
1
1
0
-40dB
1
1
1
-50dB
For example to select -47.81dB Volume the Data Byte is: 11011001
STATUS AFTER POWER ON RESET
VOLUME
BASS, TREBLE
SPKRS LF, RF, LR, RR
LOUDNESS
INPUT
STEREODEC
MUTE
NOISE BLANKER
-59.69dB
Treble = +2dB, Bass = 0dB, symmetrical
-37.5dB
OFF, -17.5dB
No input selected, GAIN = 0dB, DIFF CD GAIN = -06dB, FULLY DIFF MODE
OFF, FORCED MONO, 6dB GAIN, PILOT THRESHOLD LOW, NOISE BLANKER =11
DIRECTLY MUTED, SOFT OFF, ZEROCROSS RESET, WINDOW THRESHOLD =11
NTB = 11, NAT = 11, OVD = OFF, FSC OFF, BLEND MODE OFF, INTERNAL MPX
PATH ENABLED
DESCRIPTION OF THE NOISE BLANKER
In the normal automotive environment the MPX
signal is disturbed by ignition spikes, motors and
high frequency switches etc.
The aim of the noise blanker part is to cancel the
influence of the spikes produced by these compo-
nents. Therefore the output of the stereodecoder
is switched off for a time of 40µs (average spike
16/27
duration).
In a first stage the spikes must be detected but to
avoid a wrong triggering on high frequency noise
a complex trigger control is implemented.
Behind the trigger stage a pulse former generates
the 40µs ”blanking” pulse.
In the following section all of these circuits are de-
scribed in their function and their programming,
too (see fig.4).