AD1954 Analog Devices, AD1954 Datasheet - Page 9

• Manufacturer Part Number: AD1954
• Description: SigmaDSP Digital Audio Processor
• Manufacturer: Analog Devices

PRODUCT OVERVIEW (continued from page 1)
An extensive SPI port allows click-free parameter updates, along
with read-back capability from any point in the algorithm flow.
The AD1954 also includes ADI’s patented multibit sigma-delta
DAC architecture. This architecture provides 112 dB SNR and
dynamic range and THD+N of –100 dB. These specifications
allow the AD1954 to be used in applications ranging from low-
end “boom-boxes” to high-end professional mixing/editing systems.
The AD1954 also has a digital output that allows it to be used
purely as a DSP. This digital output can also be used to drive an
external DAC to extend the number of channels beyond the
three that are provided on the chip.
FEATURES
The AD1954 is comprised of a 26-bit DSP (48-bit with double-
precision) for interpolation and speaker processing, three multibit
sigma-delta modulators, and analog output drive circuitry. Other
features include an on-chip parameter RAM using a “safe-upload”
feature for transparent and simultaneous updates of filter coeffi-
cients. Digital deemphasis filters are also included. On-chip
input selectors allow up to three sources of serial data and mas-
ter clock to be selected. The three-channel configuration is
especially useful for 2.1 playback systems that include two satel-
lite speakers and a subwoofer. The default program allows for
independent equalization and compression/limiting for the satel-
lite and subwoofer outputs. Figure 1 shows the block diagram of
the device.
The AD1954 contains a program RAM that is booted from an
internal program ROM on power-up. Signal-processing parameters
are stored in a 256-location parameter RAM, which is initialized
on power-up by an internal boot-ROM. New values are written
to the Parameter RAM using the SPI port. The values stored in
the parameter RAM control the IIR equalization filters, the dual-
band compressor/limiter, the delay values, and the settings of the
stereo spreading algorithm.
SERIAL DATA I/O
AUX SERIAL
DATA INPUT
CLOCK I/O
MASTER
GROUP
GROUP
GROUP
SPI I/O
3
3
3
3
3
PRELIMINARY TECHNICAL DATA
NOTES
1
2
CONTROLLED THROUGH SPI CONTROL REGISTERS
DAC DOES NOT USE DIGITAL INTERPOLATION
MCLK
AUDIO
MUX
SPI PORT
MUX
DATA
3:1
3:1
1
1
(256/384/512 f
256/512f
GENERATOR
REGISTERS
REGISTERS
TRAP REG.
SAFELOAD
CONTROL
(I
2
MCLK
ZEROFLAG
S, SPI)
SERIAL
S
IN
OUT
1
S
1
IN)
3.45 (DOUBLE PRECISION)
3.23 (SINGLE PRECISION)
The AD1954 has a very sophisticated SPI port that supports
complete read/write capability of both the program RAM and
the parameter RAM. Two control registers are also provided to
control the chip serial modes, and various other optional fea-
tures. Handshaking is included for ease of memory uploads/
downloads.
The AD1954 contains four independent data-capture circuits
that can be programmed to tap the signal flow of the processor
at any point in the DSP algorithm flow. These captured signals
can be accessed either through a separate serial-out pin (which
can be connected to an external DAC or DSP, for example), or
by reading from the data-capture SPI registers. This allows the
basic functionality of the AD1954 to be easily extended.
The processor core in the AD1954 has been designed from the
ground up for straightforward coding of sophisticated compression/
limiting algorithms. The AD1954 contains two independent
compressor/limiters with RMS-based amplitude detection and
attack/hold/release controls, together with an arbitrary compression
curve that is loaded by the user into a lookup table that resides in
the parameter RAM. The compressor also features look-ahead
compression, which prevents compressor overshoots.
The AD1954 has a very flexible serial data input port that allows
for glueless interconnection to a variety of ADCs, DSP chips,
AES/EBU receivers, and sample rate converters. The AD1954
can be configured in left-justified, I
serial port compatible modes. It can support 16, 20, and 24 bits
in all modes. The AD1954 accepts serial audio data in MSB
first, two’s complement format. The part can also be set up in a
four channel serial input mode by simultaneously using serial
input mux and auxiliary serial input.
The AD1954 operates from a single 5 V power supply. It is
fabricated on a single monolithic integrated circuit and is housed
in a 44-lead MQFP or 48-lead LQFP package for operation
over the temperature range –40°C to +105°C.
PROGRAM
MEMORY CONTROLLERS
512
DATA MEMORY, 52
RAM
DATA FORMAT:
DSP CORE
35
26
22
PROGRAM
256
RESETB
RAM
22
26
MUTE DE-EMPHASIS
DAC –SW
SCOUT TRAP
DAC – L
DAC – L
COEFFICIENT
BIAS
64
ROM
2
22
2
S, right-justified, or DSP
DCSOUT
ANALOG
OUTPUTS
ANALOG
BIAS GROUP
AD1954