TDA7419_09 Datasheet, PDF (25/40 Pages) STMicroelectronics – 3 band car audio processor

TDA7419
Description of the audio processor
4.9
Subwoofer filter
The subwoofer lowpass filter has butterworth characteristics with programmable cut-off
frequency (80/120/160 Hz)
Figure 18. Subwoofer control
4.10
Spectrum analyzer
A fully integrated seven-band spectrum analyzer with programmable quality factor is
present. The spectrum analyzer consists of seven band pass filters with rectifier and sample
capacitor that stores the maximum peak signal level since the last read cycle. This peak
signal level can be read by a microprocessor at the SAout pin. To allow easy interfacing to
an analog port of the microprocessor, the output voltage at this pin is referred to device
ground.
The microprocessor starts a read cycle with the negative going clock edge at the SAclk
input. On the following positive clock edges, the peak signal level for the band pass filters is
subsequently switched to SAout. Each analog output data is valid after the time t_Sadel. A
reset of the sample capacitors is induced whenever SAclk remains high for the time t_intres.
Note that a proper reset requires the clock signal SAclk to be held at high potential. Figure
20 shows the block diagram and figure 21 illustrates the read cycle timing of the spectrum
analyzer.
Figure 19. Spectrum analyzer block diagram
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