MAS3507D Micronas Intermetall, MAS3507D Datasheet - Page 6

• Manufacturer Part Number: MAS3507D
• Description: Mpeg 1/2 Layer 2/3 Audio Decoder
• Manufacturer: Micronas Intermetall

MAS 3507D
1.2. Application Overview
The MAS 3507D can be applied in two major environ-
ments: in multimedia mode or in broadcast mode. For
both modes, the DAC 3550A fits perfectly to the
requirements of the MAS 3507D. It is a high-quality
multi sample rate DAC (8 kHz ... 50 kHz) with internal
crystal oscillator, which is only needed for generating
the decoder clock, and integrated stereo headphone
amplifier plus 2 stereo inputs.
1.2.1. Multimedia Mode
In a memory-based multimedia environment, the easi-
est way to incorporate a MAS 3507D decoder is to use
its data-demand pin. This pin can be used directly to
request input bit stream data from the host or memory
system.
While the demand pin is active, the data stream shall
be transmitted to the MAS 3507D. The bit stream clock
should be higher than the actual data rate of the
MPEG bit stream (1 MHz bit stream clock works with
all MPEG bit rates). The demand signal will be active
until the input buffer of the MAS 3507D is filled.
Fig. 1–2: Block diagram of a MAS 3507D, decoding a stored bit stream in multimedia mode
Fig. 1–3: Block diagram of a MAS 3507D in a broadcast environment
6
ROM, CD-ROM,
RAM, Flash Mem. ..
(PC, Controller)
Front-end
Receiver
Host
L3 bit stream
control I
(fixed rate)
clock
MPEG bit stream
demand signal
demand clock
2
C
I
2
C
MAS 3507D
MAS 3507D
CLKI
CLKI
I
2
S
I
2
S
3550A
A delayed response of the host to the demand signal
(by several milliseconds) or an interrupted response of
the host will be tolerated by the MAS 3507D as long as
the input buffer does not run empty. A PC might use its
DMA capabilities to transfer the data in the background
to the MAS 3507D without interfering with its fore-
ground processes.
The source of the bit stream may be a memory (e.g.
ROM, Flash) or PC peripherals, such as CD-ROM
drive, an ISDN card, a hard disk or a floppy disk drive.
1.2.2. Broadcast Mode
In environments where the bit stream is delivered from
an independent transmitter to one or more receivers,
the MAS 3507D cannot act as master for the bit
stream clock. In this mode, it synchronizes itself to the
incoming bit stream data rate by a digital PLL and gen-
erates a synchronized digital audio sample clock for
the required output sample rates.
DAC
3550A
CLKOUT
DAC
14.725 MHz
CLKOUT
14.725 MHz
line out
line out
PRELIMINARY DATA SHEET
Micronas