TDA7419_09 datasheet(25/40 Pages) STMICROELECTRONICS

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TDA7419

Description of the audio processor

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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 tSadel. A

reset of the sample capacitors is induced whenever SAclk remains high for the time tintres.

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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