TDA7402 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TDA7402' PDF : 69 Pages View PDF
Audioprocessor part
TDA7402
volume with the same value in order to get the desired output-level. In clipping situation the
open collector current generates a voltage drop at the rectifier input, which forces the
compander to decrease the gain until the clipping disappears.
It is even possible to run the compression mode and the anti-clipping mode in parallel. In
this case the maximum compander gain should be set to 29dB.
3.11.2
Characteristic
To achieve the desired compression characteristic like shown below the volume has to be
decreased by 4dB.
Figure 18. Compander characteristic
Obsolete Product(s) - Obsolete Product(s) 3.11.3
0
-10
Output Level
-20
dB
-30
-40
-50
-60
0
-8dB
2:1
-38dB
15dB
-10
-20
-30
-40
-50
-60
Input Level
dB
I2C bus timing
While the compander is working, a volume word coming from this stage is added to the I2C
bus volume word, and the volume is changed with a soft slope between adjacent steps
(Soft Step stage). As mentioned in the description of this stage, it is not recommended to
change the volume during this slope. To avoid this while the compander is working and the
volume has to be changed, the compander hold-bit is implemented (Bit 7 in the subaddress
byte). The recommended timing for changing the volume during compander ON is the
following:
1. Set the compander hold bit
2. Wait the actual Soft Step time
3. Change the volume
4. Reset the compander hold bit
The Soft Step times are in compander ON condition automatically adapted to the attack time
of the compander. In the following table the related Soft Step times are shown:
Table 6.
Attack times vs. soft-step times
Attack time
6ms
12ms
24ms
48ms
Soft Step time
0.16ms
0.32ms
0.64ms
1.28ms
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