TEXAS INSTRUMENTS DEM-DAI1742 Technical data

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DEM-DAI1742

EVALUATION FIXTURE

VCCAVCC–AVCC+

DD

GND GNDML MC MDI RST MDO GND +V

SW006

Format Control

M2, M1, M0

Opt

Coax

Digital

Audio

Receiver

DAI
(BUS)
Select

External I/F

(CN004)

JUMPER

CLKO

LRCK
DATA

FEATURES

● COMPLETE EVALUATION PLATFORM FOR

THE PCM1742 STEREO AUDIO DAC

● ONBOARD LOW-PASS FILTERS FOR THE

LEFT AND RIGHT CHANNELS

● EASY CONFIGURATION USING ONBOARD

SWITCHES AND JUMPERS

● 96kHz DIGITAL AUDIO RECEIVER ACCEPTS

S/PDIF AND OPTICAL INPUTS

● DEMONSTRATION SOFTWARE FOR

PROGRAMMING THE PCM1742’S INTERNAL
REGISTERS (REQUIRES A PC RUNNING
MICROSOFT WINDOWS® 3.1, 95, 98)

● CENTRONICS CONNECTOR FOR

INTERFACING TO A PC PARALLEL PORT
(REQUIRED FOR THE DEMONSTRATION
SOFTWARE)

SCKI

BCK

3.3V

Regulator

PCM1742

L/R Ch

V

CC

2nd-Order LPF

OPA2134

● POWER-SUPPLY REQUIREMENTS: +5V,

+15V, AND –15V

● CONNECTOR FOR OPTIONAL EXTERNAL

+3.3V POWER SUPPLY

Windows is a registered trademark of Microsoft Corp.

DESCRIPTION

The DEM-DAI1742 is a complete evaluation plat­form for the PCM1742 24-bit, 192kHz stereo audio
Digital-to-Analog Converter (DAC). All necessary
connectors and circuitry are provided for interfacing
to audio test systems and commercial audio equip­ment.

L-Channel

R-Channel

Copyright © 2001, Texas Instruments Incorporated SBAU034 Printed in U.S.A. January, 2001

HARDWARE DESCRIPTION

POWER SUPPLIES

The DEM-DAI1742 evaluation fixture requires three power
supplies for operating the PCM1742, the digital support
circuitry, and the low-pass filter op amp. Standard banana
jacks are provided for all power-supply connections.

Connector CN054 provides the +5V supply required for
VCC. It is used to power the analog sections of the PCM1742,
as well as the digital audio receiver (U002) and associated
logic (U003 and U004).

Connectors CN051 (AVCC+) and CN053 (AVCC–) are used
to power the OPA2134 dual op amp (U101) that performs
the DAC output low-pass filter function. AVCC+ may be set
from +5V to +18V, while AVCC– may be set from –5V
to –18V.

Ground connections are made at connectors CN052 and
CN055. Both are connected to the ground plane of the DEM­DAI1742 board.

In addition to the three required external power supplies, a
+3.3V supply is required for the PCM1742. The +3.3V
supply is typically derived from VCC using an onboard linear
regulator, the REG1117-3.3 (U051). A jumper must be
installed at CN057 to connect the regulator output to the
PCM1742.

A connector (CN056) is provided for connection to an
optional external +3.3V power supply. When using CN056,
the jumper at CN057 must be removed in order to disable the
regulator output.

ANALOG OUTPUTS

The left and right audio outputs are available at RCA jacks
CN104 and CN105 respectively. The outputs are taken from
the low-pass filter, which has a gain of 2. The low-pass filter
may be configured for one of two cutoff frequencies: 54kHz
or 108kHz. Typically, the 54kHz cutoff frequency is used
for all measurements.

For f
installed.

For f­be removed.

ZERO-FLAG OUTPUTS

The zero flags for the left and right channels are brought out
at connector CN103. ZFGL is the zero flag for the left
channel, while ZFGR is the zero flag for the right channel.
Refer to the PCM1742 data sheet for detailed information
regarding the zero-flag outputs.

DIGITAL AUDIO INTERFACE

A digital audio receiver (U002) is provided for easy connec­tion to S/PDIF and optical signal sources, including audio test
systems (Audio Precision, Rhode & Schwarz) and commer­cial audio equipment (CD and DVD players). The receiver
can operate at rates up to a 96kHz with 24-bit audio data.

= 54kHz, jumpers JP101 through JP106 must all be

-3dB

= 108kHz, jumpers JP101 through JP106 must all

3dB

Switches SW001 through SW003 are used to set the receiver
output data format, as shown in Table I. Table II shows the
jumper configuration for JP001 for normal operation.

SW001 SW002 SW003 RECEIVER OUTPUT DATA FORMAT

L L L 16- to 24-Bit Left-Justified
L H L 16- to 24-Bit I
H L H 16-Bit Right-Justified (or Standard)
L H H 18-Bit Right-Justified (or Standard)

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S

TABLE I. Digital Audio Receiver Configuration.

16-BIT 18-BIT 16- TO 24-BIT

JP001 JUSTIFIED JUSTIFIED I

RIGHT RIGHT 16- TO 24-BIT LEFT

JUMPER FORMAT FORMAT FORMAT FORMAT

CLKO X X X X
SCLK O O O O
GND O O O O
BCK O O O NC
BCK (L.Just.) NC NC NC O
LRCK O O O O
DATA O O O O

NOTE: O = Install Jumper; NC = Remove Jumper; X = Don’t Care,

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S JUSTIFIED

TABLE II. JP001 Jumper Configuration.

Switch SW004 is a normally open, momentary-contact push­button switch used to reset the digital audio receiver when
necessary.

The demonstration board also supports direct interfacing to
audio decoders and signal processors via connector CN004
(unpopulated). SCLK, BCK, LRCK, and DATA are avail­able and buffered by U005. In addition, +5V (VCC) and
Ground are available at CN004. Switch SW005 is used to
select between the digital audio receiver and connector
CN004 as the source of the audio interface. Table III shows
the available switch settings.

SW005
SETTING SOURCE SELECTION

INT Digital Audio Receiver (U002)
EXT Connector CN004 via Buffer U005

TABLE III. Digital Audio Source Selection.

DIP-SWITCH CONFIGURATION

Switch SW006 is not utilized for the PCM1742. It is in­cluded for future products that may be compatible with this
demonstration board. All switch elements must be set to the
OFF position for the PCM1742.

PC PARALLEL PORT/HOST CONNECTOR

The evaluation fixture includes a Centronics connector, CN003,
thatis used to connect to a PC parallel port or an alternative
host controller. This connector is utilized to access the serial
control port of the PCM1742. The serial control port is used to
program the PCM1742’s internal registers. A standard printer
cable is used to connect CN003 of the evaluation fixture to a
PC parallel port. The port signals are buffered using U006.

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DEM-DAI1742

SBAU034

SCHEMATICS

Figures 1 through 4 provide schematics for the DEM-DAI1742.

FIGURE 1. DAC Low-Pass Filters.

FIGURE 2. Power-Supply Connections.

DEM-DAI1742

SBAU034

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