TDA7406T View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TDA7406T' PDF : 49 Pages View PDF
TDA7406T
2.5 Volume Control
2.5.1 Gain/Attenuation Control
The volume control can range from a gain of 32dB up to an attenuation of 79dB; however it is not recommended
to use a gain higher than 20dB for performance reasons.
2.5.2 Soft Step Volume
When the speaker-level is changed, audible clicks could appear at the output. The root cause of those clicks
could either be a DC offset before the speaker-stage or the sudden change of the envelope of the audio signal.
With the SoftStep-feature both kinds of clicks could be reduced to a minimum and are no more audible. The
blend-time from one step to the next is programmable with four different values: 320µs, 1.28ms, 5.12ms and
20.4ms.
Figure 6. SoftStep-Timing for Volume
1dB
0.5dB
-0.5dB
SS Time
-1dB
Note: For steps more than 0.5dB (Volume) or 1dB (Speaker) the SoftStep mode should be deactivated because it could generate a hard 1dB
step during blending.
2.6 The Seven Band Equalizer
2.6.1 Equalizer Filter
Each filter is realized as a switched capacitor with a 2nd order frequency response.
There are three parameters programmable in the equalizer filter:
s Attenuation: ±15dB in 1db step resolution (Figure 7 shows the boost and cut response as a function
of frequency at a center frequency of 1kHz.)
s Center Frequency: This parameter is programmable in the filter stages 1(62/100Hz), 6(4/6.34kHz) and
7(15/16kHz). The others bands are fixed at: 157, 396, 1K and 2.5K Hertz (see Figure 8).
s Quality Factors: The four possible quality factors are 1, 1.4, 1.8 and 2.2 (see Figure 9).
The center frequency, Q, DC-mode and boost/cut can be set fully independently for each filter. Figure 10 shows
the superposition of all equalizer filter curves for different quality factors.
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