a
FEATURES
Low Cost, Pin- and Register-Compatible Alternative to
AD1848
Single-Chip Integrated
∑∆
Digital Audio Stereo Codec
Supports the Microsoft Windows Sound System*
Multiple Channels of Stereo Input and Output
Analog and Digital Signal Mixing
Programmable Gain and Attenuation
On-Chip Signal Filters
Digital Interpolation and Decimation
Analog Output Low-Pass
Sample Rates from 5.5 kHz to 48 kHz
68-Lead PLCC Package
Operation from +5 V Supply
Byte-Wide Parallel Interface to ISA and EISA Buses
Supports One or Two DMA Channels and
Programmed I/O
PRODUCT OVERVIEW
Low Cost Parallel-Port 16-Bit
SoundPort Stereo Codec
AD1846
It provides a direct, byte-wide interface to both ISA (“AT”) and
EISA computer buses for simplified implementation on a com-
puter motherboard or add-in card. The AD1846 generates en-
able and direction controls for IC buffers such as the 74_245.
The AD1846 SoundPort Stereo Codec supports a DMA re-
quest/grant architecture for transferring data with the host com-
puter bus. One or two DMA channels can be supported.
Programmed I/O (PIO) mode is also supported for control reg-
ister accesses and for applications lacking DMA control. Two
input control lines support mixed direct and indirect addressing
of twenty-one internal control registers over this asynchronous
interface.
External circuit requirements are limited to a minimal number
of low cost support components. Anti-imaging DAC output
filters are incorporated on-chip. DAC dynamic range exceeds
80 dB over the 20 kHz audio band. Sample rates from 5.5 kHz
to 48 kHz are supported from external crystals.
The Codec includes a stereo pair of
∑∆
analog-to-digital con-
verters and a stereo pair of
∑∆
digital-to-analog converters. In-
puts to the ADC can be selected from four stereo pairs of analog
signals: line, microphone (“mic”), auxiliary (“aux”) line #1, and
post-mixed DAC output. A software-controlled programmable
gain stage allows independent gain for each channel going into
the ADC. The ADCs’ output can be digitally mixed with the
DACs’ input.
(Continued on page 9)
The Parallel-Port AD1846 SoundPort
®
Stereo Codec integrates
key audio data conversion and control functions into a single in-
tegrated circuit. The AD1846 is intended to provide a complete,
single-chip audio solution for business audio and multimedia
applications requiring operation from a single +5 V supply.
*Windows Sound System is a trademark of Microsoft Corp.
SoundPort is a registered trademark of Analog Devices, Inc.
FUNCTIONAL BLOCK DIAGRAM
ANALOG
SUPPLY
DIGITAL
SUPPLY
ANALOG
L_LINE
R_LINE
L_MIC
R_MIC
L_AUX1
R_AUX1
CRYSTALS
POWER DOWN
DIGITAL
OSCILLATORS
L
GAIN
MUX
R
GAIN
∑∆
A/D
CONVERTER
16
∑∆
A/D
CONVERTER
PLAYBACK REQ
16
µ/
A
L
A
W
P
A
R
A
L
L
E
L
P
O
R
T
PLAYBACK ACK
CAPTURE REQ
CAPTURE ACK
ADR1:0
DATA7:0
CS
WR
RD
BUS DRIVER
CONTROL
HOST DMA
INTERRUPT
EXTERNAL
CONTROL
AD1846
GAIN/ATTEN/
MUTE
L
L_OUT
∑
ATTEN/
MUTE
ANALOG
FILTER
∑∆
D/A
CONVERTER
INTERPOL
ATTENUATE
DIGITAL
MIX
∑
R_OUT
∑
R
ATTEN/
MUTE
ANALOG
FILTER
∑∆
D/A
CONVERTER
REFERENCE
INTERPOL
ATTENUATE
∑
µ/
A
L
A
W
L_AUX2
R_AUX2
GAIN/ATTEN/
MUTE
CONTROL
REGS
V
REF
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
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