tda9874h NXP Semiconductors, tda9874h Datasheet - Page 13

• Manufacturer Part Number: tda9874h
• Description: Digital Tv Sound Demodulator/decoder
• Manufacturer: NXP Semiconductors

Philips Semiconductors
6.3
6.3.1
The TDA9874H has one external analog stereo input, one
mono input and one two-channel output port. Analog
source selector switches are employed to provide the
desired analog signal routing capability, which is done by
the analog crossbar switch section.
The basic signal routing philosophy of the TDA9874H is
that each switch handles two signal channels at the same
time, e.g. Left and Right, language A and B, directly at the
source. For an overview of the signal flow see Fig.5.
Each source selector switch is followed by an analog
matrix to perform further selection tasks, like putting a
signal from one input channel, say, language A, to both
output channels or for swapping left and right channel.
The analog matrix provides the functions given in Table 5.
All switches and matrices are controlled via the I
Table 5 Analog matrix functions
2000 Jun 26
handbook, full pagewidth
Digital TV sound demodulator/decoder
MODE
Description of the analog audio section
A
1
2
3
4
NALOG CROSSBAR SWITCH AND ANALOG MATRIX
L OUTPUT
mono (AM)
R input
R input
L input
L input
EXTIR
DACR
EXTIL
DACL
MATRIX OUTPUT
Fig.4 Switch diagram for the audio section.
R OUTPUT
R input
R input
L input
L input
2
source select
C-bus.
13
6.3.2
The external and mono inputs accept signal levels of up to
1.4 V (RMS). By adding external series resistors to
provide a suitable attenuation, the external input could be
used as a SCART input. Whenever the external or mono
input is selected, the output of the DAC is muted to
improve the crosstalk performance.
6.3.3
The TDA9874H comprises a two-channel audio DAC for
feeding signals from the DSP section to the analog
crossbar switch. These DACs have a resolution of 15 bits
and employ four-fold oversampling and noise shaping.
6.3.4
The output buffers provide 0 dB of gain and offer a muting
possibility. The post filter capacitors of the audio DACs are
connected to the buffer outputs.
6.3.5
The standby mode (see Section 7.3.2) disables most
functions and reduces power dissipation of the
TDA9874H, but provides no other functionality.
Internal registers may lose their information in standby
mode. Therefore, the device needs to be initialized on
returning to normal operation. This can be accomplished in
the same way as after a Power-on reset.
E
D
A
S
matrix
XTERNAL AND MONO INPUTS
UDIO OUTPUT BUFFERS
TANDBY MODE
UAL AUDIO
DAC
MGK754
OUTL
OUTR
Product specification
TDA9874H