Analog Devices AD1852EB Datasheet

24-Bit Stereo DAC

T

a

OVERVIEW

The EVAL-AD1852-EB evaluation board permits testing and
demonstrating the high-performance AD1852 24-bit stereo
DAC. An input signal is required in either optical or coaxial
SPDIF format or, alternatively, directly via a 10-pin header in

2

S, left justified, right justified, or DSP modes. A second 10-pin

I
header and DB-9 connector allows control of the internal regis­ters from an external SPI controller.

Power requirements are a clean 9 V to 12 V dc source for the
digital section and a clean ±12 V dc for the analog section. The
positive supplies can be paralleled if desired. On-board regulators
derive separate “clean” 5 V dc supplies for the digital and analog
sections. Audio output is provided from two RCA phono jacks.

AD1852 OVERVIEW

The AD1852 is a complete 16-/20-/24-bit single-chip digital
audio, stereo digital-to-analog converter (DAC). It is comprised
of a multibit sigma-delta modulator with dither, continuous
time analog filters, and differential analog outputs. Other fea­tures include an on-chip stereo attenuator, de-emphasis filter,
selectable interpolator and mute control, programmed through

Evaluation Board

EVAL-AD1852EB

an SPI-compatible serial control port. The AD1852 is fully
compatible with all known DVD formats including 96 kHz and
192 kHz sample rates and 24 bits. It also is backwards-compatible
by supporting 50 µs/15 µs digital de-emphasis intended for
“redbook” Compact Discs, as well as de-emphasis at 32 kHz
and 48 kHz sample frequencies.

The AD1852 has a very simple, but very flexible, serial data
input port that allows for a glueless interconnection to a variety
of ADCs, DSP chips, digital interface receivers (DIR) and
asynchronous sample rate converters (ASRC). The AD1852
can be configured in left-justified (LJ), I2S, right-justified (RJ),
or DSP serial port compatible modes. It can support 16, 20, and
24 bits in all modes. The AD1852 accepts serial audio data in
MSB first, twos complement format. A power-down mode is
offered to minimize power consumption when the device is
inactive. The AD1852 operates from a single 5 V power supply.
It is fabricated on a single monolithic integrated circuit and
housed in a 28-lead SSOP package. Normal operation over the
temperature range 0°C to 70°C is guaranteed.

The AD1852 data sheet gives a more complete description of
operation.

J2 EXT DATA

J1 RCA JACK

SPDIF INPUT

OPTICAL

INPUT

SPDIF/EXT(J2)

DEEMPHASIS

S4

MUTE

RESET

S3

S2

S6

U1

TOS LINK

S1

SIGNAL

SOURCE

SELECT

RESET

GENERATOR

FUNCTIONAL BLOCK DIAGRAM

S5

U4

I/F

MUX

DS3
DEEMPH

DS4
VERF

INTERPOLATION

MODE

SPI CONTROL

PORTS

INTERFACE

MODE

U11

U2

DIR

U8

U10

RESET

JP1

J3/J5

U5

U3

DAC

AD1852

U9B

U9A

J6
LEFT

J7
RIGHT

DS1
ZERO LEFT

DS2
ZERO RIGH

REV. 0

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

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] World Wide Web Site: http://www.analog.com
Fax: [phone] © Analog Devices, Inc., 2001

EVAL-AD1852EB

FUNCTIONAL DESCRIPTION

The AD1852 evaluation board presents a reference design that
can be used as a suggested layout and circuit implementation,
which will deliver optimal performance from the audio DAC. As
far as is possible on an evaluation board, current assembly methods
and components are used. Most components are surface mount
devices and a four-layer printed circuit board is used with full
internal power and ground planes for best noise performance.
For guidance, a schematic, bill of materials, PLD source code,
and PCB plots are included in this document.

POWER SUPPLIES

The PC board is divided into analog and digital sections, each
with separate power supplies, to facilitate testing. The digital
power supply input is via binding post terminals J8 and J9. The
recommended digital supply is 12 V dc at 110 mA ± 25 mA. An
on-board voltage regulator (U6) provides 5 V dc, ±5% to the
digital circuitry. The analog power supply inputs are binding
posts, J10, J11, and J12. Recommended analog supply is 12 V
dc at 50 mA ± 10 mA and –12 V dc at –20 ± 5 mA. An on­board, low noise voltage regulator, (U7) provides 5 V dc, ±5%
to the analog power pins of the AD1852 DAC.

DIGITAL AUDIO SIGNAL INPUTS

RCA phone jack, (J1) and optical TOSLink input (U1) may be
used for standard SPDIF or AES/EBU input signals. J1 is termi­nated with a 75 Ω resistor. Switch S1 selects between J1 and U1
inputs and feeds the selected signal to the digital interface receiver
(U2). Switch SPDIF/EXT (S3) controls CPLD (U4) and U11,
which is used to switch signals between the SPDIF input (J1)
and the direct input, via the 10-pin header J2, EXT DATA
INTERFACE.

The EXT DATA INTERFACE input permits buffered (U4,
M4–64/32 and U11, HC00) access to the BCLK, L/RCLK,
SDATA and MCLK inputs to the AD1852 DAC. This permits
testing with left-justified, I
Note that with right-justified input data, the AD1852 control
register must be programmed for the correct number of data
bits, i.e., 16, 20 or 24 bits. When using the direct input header,
it is necessary to provide all four signals, MCLK, BCLK, L/RCLK
and SDATA. A termination network (RC1), consisting of a series
connected 100 Ω resistor and a 47 pF capacitor, is shunted
across each signal line to reduce line reflections. A 10 kΩ pull­up network (RT1) ensures the inputs are not floating in the
absence of an external data source.

EXTERNAL SPI CONTROL PORT

An external control port, SPI CONTROL PORT (J3), is pro­vided, via a 10-pin header, so that the internal volume controls
and control registers can be programmed from an external host
or microcontroller. This port accepts serial data to indepen­dently set the left/right volume or the operating mode of the
AD1852 by programming the contents of three internal 16-bit
registers. When setting the volume, a 16-bit control word has
14 bits allocated to the left or right volume control, giving a
total range of 84 dB. Details of the signal format and timing are
discussed in the AD1852 data sheet.

2

S or right-justified, serial input modes.

An additional connector, PC PORT (J5), has been provided to
permit connection to the parallel port of a computer. A termi­nation network (RC2) consisting of a series-connected 100 Ω
resistor and a 47 pF capacitor, is shunted across each signal line
to reduce line reflections. Additionally, a Schmitt trigger (U5)
reduces the effects of noise and line reflections. A 10 kΩ pull-up
network (RT2) ensures the inputs are not floating in the absence
of an external data source.

PC LabView software (LVAD1852EB.zip) can be downloaded
from the Analog Devices, Inc., Digital Audio website, (http://
www.analog.com/techsupt/eb/lin_eb/ad1852/ad1852.html) to
program the internal control registers and set the left and right
volume levels. An interface cable connects between the PC
parallel printer port (LPTn) 25-pin Dsub connector and the
9-pin Dsub (J5) connector on the evaluation board. A suitable
cable is Belkin Modem cable, part number 589604, F2L088-06

The pin-out for this cable in shown, in the table below, for users
who wish to make their own cable.

Table I.

PC EVAL Board

Function (DB-25 Male) (DB-9 Female)

Data 6 8 1
Data 1 3 2
Data 0 2 3
GND 20 4
Data 5 7 5
Data 4 6 6
Data 2 4 7
Data 3 5 8
GND 22 9
Chassis Shield GND Case Case

NOTE: When setting the internal control registers via the SPI
port, it is essential to pull the corresponding external pins low as
they are wire-OR’d with the SPI control registers. This applies
to the interpolation mode pins, via JP1 (192/48 P7, 96/48 P10),
the power down/reset pin, (RESET), the mute pin, (MUTE), the
interface mode pins (IDPM1, IDPM0) and the de-emphasis
control pin, (DEEMPH). Also note that when the right-justified
interface mode is selected, either via the external pins or via the
SPI port, the default data word width is 24 bits. It is necessary
to select 16 or 20 bits via the SPI control register if these word
lengths are required.

AUDIO SIGNAL OUTPUTS

RCA jacks J6 and J7 provide LEFT and RIGHT audio output
signals. The output is filtered with a low-pass anti-image filter
using an OP275 audio op amp (U9) which also converts the dif­ferential outputs of the AD1852 to single ended signals. The
filter –3 dB cut-off frequency is 100 kHz and has an approxi­mate Third Order Bessel (linear phase) response. The output
source impedance is approximately 600 Ω. The full-scale output
signal is 2 V rms (5.6 V p-p).

–2–

REV. 0

EVAL-AD1852EB

SWITCH AND JUMPER FUNCTIONS

• S1 is used to select between the RCA SPDIF INPUT (J1) and
the TOSLINK optical input, (U1). The SPDIF signal is a
self-clocking, Manchester-encoded signal that is decoded by
the digital interface receiver (DIR, U2) to extract the left and
right digital audio data and associated status signals.

• S2 is used to activate the AD1852 MUTE hardware function.

• S3 switches the CPLD (U4) digital input signals between the
digital interface receiver (DIR, U2) and the EXT DATA
INTERFACE (J2). The CPLD (U4) digital outputs go directly
to the AD1852 DAC. In addition to the digital audio data
signals, S3 also switches the master clock between the DIR
(U2) and the Ext Data I/F input (J2) via the NAND gate (U11).

• S4 is used to enable the internal AD1852 DEEMPHASIS
digital filter. This is confirmed by lighting the DEEMPH
LED, (DS3).

• S5 selects the serial interface modes for the SPDIF receiver
(U2) and the AD1852 DAC (U3):

Table II. Serial Interface Mode Selection

S5
Position AD1852 Serial Interface Mode IDPM1 IDPM0

0 Left Justified, 16 to 24 Bits 1 0
1I
2 Right Justified, (U2 (DIR) is 0 0

3 DSP Word Sync, 16- to 24-Bits 1 1
4 Serial Mode is set through SPI 0 0

5 Spare – Not Used
6 Spare – Not Used
7 Spare – Not Used

2

S, 16 to 24 Bits 0 1

set for 24 Bits. Program the
AD1852 via the SPI port for
24 Bits if using U2).

Port using LabView Software.

• S6 provides a RESET function via reset generator U8
(ADM811TART) and a “clean” 200 ms delay after release.
U8 also provides a 200 ms delayed reset release at power-up.
This ensures that the digital interface receiver (DIR, U2) and
the AD1852 are correctly initialized after power-up and their
internal registers are set to the correct default values.

• JP1 Header is used to select the internal interpolation ratio for
the AD1852. Jumpers are selected according to the following
table. The default is 8× interpolation, i.e., both jumpers are
installed. NOTE: When the internal registers are used, the
effective logic state is the logical OR of the external pin and
the program register, hence both jumpers should be in place
so that the programmable registers can correctly set the state
of the control bits.

Table III.

Interpolation Ratio (SR) 96/48 (JP1-1) 192/48 (JP1-2)

8× (32 kHz to 50 kHz) 0 0
4× (64 kHz to 100 kHz) 0 1
2× (128 kHz to 200 kHz) 1 0
Not Allowed 1 1

Note: 0 = Closed.

Indicator Display LEDs

Five red LED indicators are provided for status indication.

• Display LEDs DS1, ZL and DS2, ZR show that the AD1852
is detecting a zero signal in either the left or right channel
respectively.

• Display LED DS3, DEEMPH, indicates that either switch S4
has selected de-emphasis or that the incoming SPDIF signal
has the EMPHASIS status bit set. In either case, illumination
of DS3 indicates that the DEEMPHASIS filter function of the
AD1852 is active.

• Display LED DS4, VERF, indicates that the digital interface
receiver has detected an error condition in the received SPDIF
signal or the SPDIF Invalid status bit has been set.

• Display LED DS5, POWER, shows the presence of 5 V dc on
the analog 5 V power supply.

INTEGRATED CIRCUIT FUNCTIONS

There are 11 active devices on the AD1852 evaluation board.
Following is a brief description of the function of each part.

• U1 (TORX173) is the Toshiba Digital Audio Optical
(TOSLink) Receiver. This part accepts a visible red SPDIF­modulated signal and converts it to a standard TTL digital
signal suitable for input to the digital audio receiver (U2).

• U2 (CS8414-CS) digital audio interface receiver, (DIR) receives
and decodes the serial SPDIF, digital audio encoded signal.
This signal is Manchester modulated and is self-clocked at a
multiple of the encoded SPDIF sample rate. Four digital
audio signals are decoded by the CS8414. The serial data
SDATA, the master clock at 256 F
frame clock L/RCLK and the serial bit clock at 64 F

, MCLK, the left/right

S

, BCLK.

S

• U3 (AD1852JRS) is the high performance stereo DAC.
Depending upon selected modes of operation, (JP1) sample
rates up to 192 kHz and 24 bits may be tested by changing the
internal interpolation ratio. The interface mode can be selected
for Left Justified (LJ), I

2

S or Right Justified (RJ) by means of
the Interface Mode switch (S5). Internal registers of the
AD1852 can be programmed via the PC Port (J5) or via the
SPI Control Port, header (J3). Mute is controlled directly by
the control switch S2. The De-emphasis filter can be turned
on with the switch DEEMPH (S4) or pre-emphasis may be
detected and enabled by the SPDIF receiver.

• U4 (M4-64/32) is a Vantis CPLD and has been programmed
to provides input signal MUX selection, LED buffering and
switch decoding for the different interface modes. The output
interface mode of the DIR (U2) must be compatible with the
input to the AD1852 (U3) and this is selected at the same
time as the mode for the AD1852 is selected, with switch
Interface Mode (S5). S5 is decoded to drive the DIR mode
pins (M0-3) and AD1852 mode pins (IDPM0) and (IDMP1).
The source code in included in Appendix A. Note: Because of
excessive jitter degradation in CPLDs, a separate IC (U11) is
used to select the MCLK input to the AD1852.

• U5 (74HC14) provides Schmitt trigger buffering for the SPI
Control Port (J3) and PC Port (J5) signals. This helps to
reduce problems due to noise and ringing on the signal lines.

• U6 (LM317) provides 5 V dc low voltage regulation for the
digital section of the evaluation board.

REV. 0

–3–

EVAL-AD1852EB

• U8 (ADM811TART) is a RESET generator that provides
a debounced 200 ms reset signal from the push button (S3)
or on power up. The reset is active if the 5 V supply drops
below 3 V.

• U7 (AD3303-5.0) is a low noise 5 V dc regulator for the ana­log section of the AD1852.

• U9 (OP275) is a low noise and distortion, audio op amp. U9
provides differential-to-single-ended conversion and a low­pass anti-image filter. A third order low-pass Bessel filter
response is implemented with a –3 dB corner frequency of
100 kHz and a 60 dB/decade roll-off. This type of filter is
characterized by a linear phase response and fast transient
response without overshoot.

• U10 (74HC00) is used to provide a reset code to the digital
interface receiver (U2), pins M0–3, at power up and also sends
the correct interface code to ensure the digital output for­mat matches the input of the DAC.

• U11 (74HC00) is used to select the correct master clock
source for the DAC when it is switched between the SPDIF
receiver (U2) and the Ext Data Interface (J2). A discrete logic
gate is used for this function, because of the excessive jitter
that modulates high-frequency clock signals when they are
handled by PLDs.

PERFORMANCE SPECIFICATIONS

Typical performance, for a sample rate of 48 kHz, is tabulated
below.

1. SNR, A-Weighted –114 dBFS ± 1 dB

2. DNR, A-Weighted –114 dBFS ± 1 dB

3. THD+N –102 dBFS ± 2 dB

4. Frequency Response ± 0.2 dB, 10 Hz to 20 kHz

5. Noise Floor –145 dBFS

6. Full-Scale Audio Output 2 V rms

ATTACHMENTS

The following is included for your convenience.

• Appendix A: ABEL Source Code for Vantis MACH4-64/32
CPLD.

• Appendix B: Set of Schematics, Figures 1 and 2.

• Appendix C: PCB plots showing the silkscreen layer, top
signal layer, ground planes, power planes, and the bottom
signal layer, Figures 3–7.

FURTHER INFORMATION

Ordering information: order number is EVAL-AD1852EB.

For application questions, please contact our Central Applica­tions Department at 1-781-937-1428 for assistance.

–4–

REV. 0

EVAL-AD1852EB

APPENDIX A

MODULE IF_Logic

TITLE ‘AD1852 EVB Logic’

//===================================================================================

// FILE: 1852ext.abl
// REVISION DATE: 11-01-99 (comment revisions on 2-9-00)
// REVISION BY: Brian Wachob
// REVISION: 3.0 (plus comments)
//
//
// PREVIOUS FILE: 1852r9.abl, AD1852v8.abl
// PREVIOUS DATE: 10-01-99
// PREVIOUS REVISION: 2.0
//
// ORIGINAL AUTHOR: Larry Hurst
//
// BOARD REV.: This code is written for the “AD185_ REV 1” eval. boards
// (with, of course, an AD1852 DAC installed on the eval. board)
//
// DESCRIPTION:
//
// This chip selects between the External Data Interface header (J2) and the
// onboard CS8414 DIR (U2) for the AD1852 DAC input signals, depending upon
// the SPDIF/EXT switch position (S3). When the DIR is the selected signal
// source the digital audio signals, SDATA, BCLK and LRCLK also appear at the
// external Data Interface header (J2) as outputs.
//
// It also decodes the Interface Mode Switch(S5) and sets the interface mode
// pins for both the CS8414 DIR and the AD1852 DAC and corrects the CS8414
// output signals for LJ, RJ, and DSP modes, to match the signal requirements
// for the AD1852.
//
// It also decodes signals from LabView SPI port control software so that it
// can correctly set the interface mode pins for the CS8414 and correctly
// format the CS8414 output signal for LJ, RJ, and DSP modes. (This
// functionality is required when the SPI port is used to set the data format
// used by the DAC instead of setting it directly via the IDPM pins with the
// Interface Mode Switch, S5.)
//
// It also decodes the Deemphasis control signal from the CS8414 (U2) and
// DEEMPH switch(S4), enables and buffers the output master clock and the
// VERF signal from the CS8414.
//
// Finally, the CPLD buffers and drives the status LEDs.
//
//=============================================================================
LIBRARY ‘MACH’;
MACH_SLEW(FAST,2,MCLK:MCLKO);

DECLARATIONS
// IF_Logic DEVICE ‘M4-64/32-15VC’;

“INPUTS ———————————————————————————————————
// TDI, TCK, TMS pin 4, 7, 26; //JTAG I/P’s
SLCT_C, SLCT_B, SLCT_A pin 15, 19, 14; //Interface Mode Select
ISDATA, IMCLK, ILRCLK, IBCLK pin 1, 5, 9, 10; //DIR I/P’s
VERF, NPREEMPH, NDEEMPH pin 44, 8, 13; //DAC Control
SPDIF_EXT pin 12; //DAC Signal Source Select
ZR, ZL pin 24, 34; //DAC ZERO Signals
EMCLK pin 27; //External MCLK Input

REV. 0

–5–