TDA7514 datasheet(70/74 Pages) STMICROELECTRONICS

70 / 74 page

TDA7514

70/74

5.4.13 AM MODE 2

In this operation mode the detector operates in a much more straightforward configuration: the instanta-

neous AM audio level is compared with a fixed programmable threshold, and the comparison result acti-

vates the retriggerable monostable. The advised programmed threshold corresponds to an equivalent

140% AM modulation level.

5.5 AUDIO PROCESSOR SECTION

5.5.1

INPUTS

The audio processor input section features a main channel multiplexer, a rear channel multiplexer (RSA,

Rear Seat Audio function), an input gain stage and autozero circuit.

The main channel multiplexer allows connecting the following sources to the main audio processing path:

– 1 quasi-differential source;

– 1 stereo differential source;

– 1 mono differential source;

– tuner output (AM, FM);

– beep generator.

The RSA selector (see speaker output section) can connect the rear speaker outputs to the following

sources bypassing all the tone and volume control:

– 1 quasi-differential source;

– 1 stereo differential source;

– tuner output (AM, FM).

The different sources are subjected to the following input attenuations:

– quasi-differential source: -4 dB

– stereo differential source: 0 dB

– mono differential source: -4 dB.

The main channel signal path features an input gain stage (0..+15 dB, 1 dB step) to equalize the different

source levels and the autozero circuitry that removes the DC offset generated between the input pins and

the input gain stage output.

The autozero procedure is automatically run every time byte 0 of the audio processor I2C software is ad-

dresses, that is every time the main source is changed or the input gain is changed. In case the new

source is the stereo decoder the source change must be preceded by opening the stereo decoder input

for a time long enough to discharge the stereo decoder internal filters (see stereo decoder input section).

The same is true even when the source is switched from AM to FM and vice-versa. The autozero proce-

dure can be manually activated through a dedicated bit, and can be prevented from running by setting a

different dedicated bit. The beep generator is considered a main channel source, and it can generate a

500 Hz, 1 kHz, 2 kHz, 3 kHz tone.

5.5.2

SOFT MUTE

The input stage is followed by a soft mute stage aimed at automatically and smoothly driving the audio

processor from its current state into a full mute condition. The overall transition time is software selectable.

It is possible to control the stereo decoder RDS AF update mute circuits (input impedance open switch

("high ohmic mute"), stereo decoder mute and PLL hold) from the audio processor soft mute.

5.5.3

LOUDNESS FILTER

The TDA7514 features a loudness function made up by a 20 dB attenuator in 1 dB steps, a second order

LP filter with programmable corner frequency and a defeatable high pass filter with programmable corner

frequency.

TDA7514 Arkusz danych(PDF) 70 Page - STMicroelectronics

TDA7514 Arkusz danych(HTML) 70 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74

Arkusz danych Pobierz

Link URL