TDA9875 datasheet(13/92 Pages) PHILIPS

13 / 92 page

1998 Feb 13

Philips Semiconductors

Preliminary speciﬁcation

Digital TV Sound Processor (DTVSP)

TDA9875

6.2.1

LEVEL SCALING

All input channels to the digital crossbar switch (except for

the loudspeaker feedback path) are equipped with a level

adjust facility to change the signal level in a range of

±15 dB. It is recommended to scale all input channels to be

15 dB below full-scale (

−15 dB full-scale) under nominal

conditions.

6.2.2

NICAM PATH

The NICAM path has a switchable J17 de-emphasis.

6.2.3

FM (AM) PATH

A high-pass filter suppresses DC offsets from the

FM demodulator due to carrier frequency offsets and

supplies the monitor/peak function with DC values and an

unfiltered signal, e.g. for the purpose of carrier detection.

The de-emphasis function offers fixed settings for the

supported standards (50

µs, 60 µs, 75 µs and J17).

An adaptive de-emphasis is available for

Wegener-Panda 1 encoded programs.

A matrix performs the dematrixing of 1

⁄2(L + R) and

R to L and R signals, of 1

⁄2(L + R) and 1⁄2(L − R) to L and R

signals or of channel 1 and channel 2 to L and R signals.

6.2.4

NICAM AUTO-MUTE

If NICAM is received and the signal quality becomes poor,

the digital crossbar switch switches automatically to FM

and switches the matrix to channel 1. The automatic

switching between NICAM and channel 1 (FM or AM)

reception depends on the NICAM bit error rate.

The auto-mute function can be disabled via the I2C-bus.

6.2.5

MONITOR

This function provides data words from a number of

locations of the signal processing paths to the I2C-bus

interface (2 data bytes). Signal sources include the

FM demodulator outputs, most inputs to the digital

crossbar switch and the inputs to the loudspeaker channel

of the ADC. Source selection and data read-out is

performed via the I2C-bus.

Optionally, the peak value can be measured instead of

simply taking samples. The internally stored peak value is

reset to zero when the data is read via the I2C-bus.

The monitor function may be used, for example, for signal

level measurements or carrier detection.

6.2.6

LOUDSPEAKER (MAIN) CHANNEL

The matrix provides the following functions; forced mono,

stereo, channel swap, channel 1, channel 2 and spatial

effects.

There are fixed coefficient sets for spatial settings of 30%,

40% and 52%.

The Automatic Volume Level (AVL) function provides a

constant output level of

−23 dB full-scale for input levels

between 0 dBFS and

−29 dB full-scale. There are some

fixed decay time constants to choose from, i.e. 2, 4 and

8 seconds.

Pseudo stereo is based on a phase shift in one channel via

a 2nd-order all-pass filter. There are fixed coefficient sets

to provide 90 degrees phase shift at frequencies of

150, 200 and 300 Hz.

Volume is controlled individually for each channel ranging

from +24 dB to

−83 dB with 1 dB resolution. There is also

a mute position. For the purpose of a simple control

software in the microcontroller, the decimal number that is

sent as an I2C-bus data byte for volume control is identical

to the volume setting in dBs (e.g. the I2C-bus data

byte +10 sets the new volume value to +10 dB).

Balance can be realized by independent control of the left

and right channel volume settings.

Contour is adjustable between 0 dB and +18 dB with 1 dB

resolution.

Bass is adjustable between +15 dB and

−12 dB with 1 dB

resolution and treble is adjustable between

±12 dB with

1 dB resolution.

For the purpose of a simple control software in the

microcontroller, the decimal number that is sent as an

I2C-bus data byte for contour, bass or treble is identical to

the new contour, bass or treble setting in dBs (e.g. the

I2C-bus data byte +8 sets the new value to +8 dB).

Extra bass boost is provided up to 20 dB with 2 dB

resolution. The implemented coefficient set serves merely

as an example on how to use this filter.

The beeper provides tones in a range from approximately

400 Hz to 30 kHz. The frequency can be selected via the

I2C-bus. The beeper output signal is added to the

loudspeaker and headphone channel signals. The beeper

volume is adjustable with respect to full-scale between

0 dB and

−93 dB with a 3 dB step resolution. The beeper

is not effected by mute.

TDA9875 Datasheet(PDF) 13 Page - NXP Semiconductors

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