TDA7513T datasheet(23/59 Pages) STMICROELECTRONICS

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TDA7513T

5.4.10DC Mode

In this mode the DC gain is increased by 5.1dB. In addition the programmed center frequency and quality

factor is decreased by 25%: this can be used to realize different center frequencies or quality factors with

respect to the values listed in the "BASS" section.

5.4.11MID

There are 3 parameters programmable in the mid filter stage (see figs. 10, 11 & 12):

5.4.12Attenuation

Figure 10 shows the attenuation as a function of frequency at a center frequency of 1kHz.

5.4.13Center Frequency

Figure 11 shows the four possible center frequencies: 500Hz, 1kHz, 1.5kHz and 2kHz.

5.4.14Quality Factor

Figure 12 shows the two possible quality factors (1 and 2) at a center frequency of 1kHz.

5.4.15TREBLE

There are two parameters programmable in the treble filter stage (see figs 13, 14):

5.4.16Attenuation

Figure 13 shows the attenuation as a function of frequency at a center frequency of 17.5kHz.

5.4.17Center Frequency

Figure 14 shows the four possible Center Fre-quencies: 10, 12.5, 15 and 17.5kHz.

5.4.18AC Coupling

In some applications additional signal manipulations are desired such as surround-sound processing or

more extensive band equalizing. For this purpose a AC-Coupling is placed before the Speaker-attenua-

tors, which can be activated or internally shorted by Bit7 in the APSD data byte 0. The input impedance

of the AC Inputs is 25k

Ω. The external AC coupling is advised for those applications where very low-level

"pop" performance is a must.

5.4.19Speaker Attenuator

The speaker attenuators have exactly the same structure and range as the Volume stage.

5.5 STEREODECODER

The stereodecoder part of the present device (see Fig. 15) contains all functions necessary to demodulate

the MPX signal such as pilot tone-dependent MONO/STEREO switch as well as "stereoblend" and "high-

cut" functions.

Stereodecoder Mute

The device has a fast and easy-to-control RDS mute function meant for "freezing" the stereo decoder sta-

tus during the RDS AF check time period. When this function is invoked three effects take place:

•1 the stereo decoder input impedance changes to infinity (condition known as high-ohmic input); this

prevents the decoupling capacitor between the pins #TUNER_OUT (tuner output) and #TUNER_IN

(stereo decoder input) to be discharged by a channel with a potentially different DC output for the

duration of the AF check;

•2 the stereo decoder PLL pilot detector is held at the current value;

•3 the external capacitor of the multipath detector used inside the stereo decoder for quality control is

disconnected from the dection circuit in order to make quality checking the AF faster.

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