SAA2501 Datasheet, PDF (6/52 Pages) NXP Semiconductors – Digital Audio Broadcast DAB decoder

Philips Semiconductors
Digital Audio Broadcast (DAB) decoder
Preliminary specification
SAA2501
SYMBOL
TMS
TDI
FSCLK384
FSCLKM
MCLK24
PIN
DESCRIPTION
40 boundary scan test mode select input
41 boundary scan test data input
42 sample rate clock frequency indication input
43 sample rate clock source selection for the master input
44 master clock frequency indication input
TYPE
I
I
I
I
I
dbook, full pagewidth
RESET 1
FSCLK 2
FSCLKIN 3
MCLK 4
VDD1 ₅
GND1 6
MCLKOUT 7
MCLKIN 8
X22OUT 9
X22IN 10
STOP 11
SAA2501
33 FDFSY
32 FDAI
31 FDAO
30 WS
29 SCK
28 GND3
27 FDEF
26 SD
25 L3MODE
24 L3DATA
23 L3CLK
MBE113
Fig.2 Pin configuration (QFP44).
7 FUNCTIONAL DESCRIPTION
7.1 Coding system
The perceptual audio encoding/decoding scheme defined
within the “ISO/IEC 11172-3 MPEG Standard” allows for a
high reduction in the amount of data needed for digital
audio whilst maintaining a high perceived sound quality.
The coding is based upon a psycho-acoustic model of the
human auditory system. The coding scheme exploits the
fact that the human ear does not perceive weak spectral
components that are in the proximity (both in time and
frequency) of loud components. This phenomenon is
called masking.
For layers I and II of ISO/MPEG the broadband audio
signal spectrum is split into 32 sub-bands of equal
bandwidth. For each sub-band signal a masking threshold
is calculated. The sub-band samples are then
re-quantized to such an accuracy that the spectral
distribution of the re-quantization noise does not exceed
the masking threshold. It is this reduction of representation
accuracy which yields the data reduction. The
re-quantized sub-band signals are multiplexed, together
with ancillary information regarding the actual
re-quantization, into a MPEG audio bitstream.
January 1995
6