FEATURES
Dual Serial Input, Voltage Output DACs
Single +5 Volt Supply
0.005% THD+N
Low Power –50 mW
115 dB Channel Separation
Operates at 83 Oversampling
16-Pin Plastic DIP or SOIC Package
APPLICATIONS
Multimedia Workstations
PC Audio Add-In Boards
Portable CD and DAT Players
Automotive CD and DAT Players
Noise Cancellation
PRODUCT DESCRIPTION
The AD1866 is a complete dual 16-bit DAC offering excellent
performance while requiring a single +5 V power supply. It is
fabricated on Analog Devices’ ABCMOS wafer fabrication
process. The monolithic chip includes CMOS logic elements,
bipolar and MOS linear elements and laser trimmed, thinfilm resistor elements. Careful design and layout techniques
have resulted in low distortion, low noise, high channel separation and low power dissipation.
The DACs on the AD1866 chip employ a partially segmented
architecture. The first three MSBs of each DAC are segmented
into 7 elements. The 13 LSBs are produced using standard
R-2R techniques. The segments and R-2R resistors are laser
trimmed to provide extremely low total harmonic distortion.
The AD1866 requires no deglitcher or trimming circuitry.
Each DAC is equipped with a high performance output amplifier. These amplifiers achieve fast settling and high slew rate,
producing ±1 V signals at load currents up to ±1 mA. The buffered output signal range is 1.5 V to 3.5 V. The 2.5 V reference
voltages eliminate the need for “false ground” networks.
A versatile digital interface allows the AD1866 to be directly
connected to all digital filter chips. Fast CMOS logic elements
allow for an input clock rate of up to 16 MHz. This allows for
operation at 2×, 4×, 8×, or 16× the sampling frequency (where
F
= 44.1 kHz) for each channel. The digital input pins of the
S
AD1866 are TTL and +5 V CMOS compatible.
Dual 16-Bit Audio DAC
AD1866*
FUNCTIONAL BLOCK DIAGRAM
16-BIT
DAC
16-BIT
SERIAL
REGISTER
16-BIT
SERIAL
REGISTER
16-BIT
DAC
CLK
DGND
VBR
V
DL
DR
LR
1
L
2
LL
3
4
5
6
7
8
The AD1866 operates on +5 V power supplies. The digital
supply, V
, can be separated from the analog supply, VS, for re-
L
duced digital feedthrough. Separate analog and digital ground
pins are also provided. In systems employing a single +5 volt
power supply, V
and VS should be connected together. In bat-
L
tery operated systems, operation will continue even with reduced supply voltage. Typically, the AD1866 dissipates 50 mW.
The AD1866 is packaged in either a 16-pin plastic DIP or a
16-pin plastic SOIC package. Operation is guaranteed over the
temperature range of –35°C to +85°C and over the voltage
supply range of 4.75 V to 5.25 V.
PRODUCT HIGHLIGHTS
1. Single supply operation @ +5 V.
2. 50 mW power dissipation.
3. THD+N is 0.005% (typical).
4. Signal-to-Noise Ratio is 95 dB (typical).
5. 115 dB channel separation (typical).
6. Compatible with all digital filter chips.
7. 16-pin DIP and 16-pin SOIC packages.
8. No deglitcher required.
9. No external adjustments required.
AD1866
V
REF
V
REF
L
V
16
B
V
15
S
L
V
14
O
NRL
13
AGND
12
11
NRR
10
V
R
O
V
9
S
*Protected by U.S. Patent Nos: 3,961,326; 4,141,004; 4,349,811; 4,857,862;
and patents pending.
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
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: 617/329-4700Fax: 617/326-8703
Page 2
AD1866–SPECIFICA TIONS
(TA = +258C and +5 V supplies unless otherwise noted)
MinTypMaxUnit
RESOLUTION16Bits
DIGITAL INPUTSV
IH
V
IL
I
, VIH = V
IH
I
, VIL = DGND–10.0µA
IL
L
2.4V
0.8V
1.0µA
Maximum Clock Input Frequency13.5MHz
ACCURACY
Gain Error±3% of FSR
Gain Matching±3% of FSR
Midscale Error±30mV
Midscale Error Matching±10mV
Gain Linearity Error±3dB
Digital Inputs to DGND . . . . . . . . . . . . . . . . . . . –0.3 V to V
*Stresses greater than those listed under “Absolute Maximum Ratings” may cause
permanent damage to the device. This is a stress rating only and functional
operation of the device at these or any other conditions above those indicated in the
operational section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the AD1866 features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
PIN CONFIGURATION
16-BIT
DAC
1
2
16-BIT
SERIAL
REGISTER
3
4
5
16-BIT
SERIAL
REGISTER
6
7
16-BIT
DAC
8
CLK
DGND
VBR
V
L
LL
DL
DR
LR
AD1866
V
REF
V
REF
PinMnemonicDescription
L
V
16
B
V
15
S
V
L
14
O
NRL
13
AGND
12
11
NRR
10
R
V
O
V
9
S
11V
L
12LLLeft Channel Latch Enable Pin
13DLLeft Channel Data Input Pin
14CLKClock Input Pin
15DRRight Channel Data Input Pin
16LRRight Channel Latch Enable Pin
17DGNDDigital Common Pin
18V
19V
AD1866N–35°C to +85°CPlastic DIPN-16
AD1866R–35°C to +85°CSOICR-16
AD1866R-REEL–35°C to +85°CSOICR-16
–4–
REV. 0
Page 5
Definition of Specifications–AD1866
TOTAL HARMONIC DISTORTION + NOISE
Total harmonic distortion plus noise (THD+N) is defined as
the ratio of the square root of the sum of the squares of the amplitudes of the harmonics and noise to the amplitude of the fundamental input frequency. It is usually expressed in percent (%)
or decibels (dB).
D-RANGE DISTORTION (EIAJ SPECIFICATION)
D-Range distortion is the ratio of the amplitude of the signal at
an amplitude of –60 dB to the amplitude of the distortion plus
noise. In this case, an A-weight filter is used. The value specified for D-range performance is the ratio measured plus 60 dB.
SIGNAL-TO-NOISE RATIO
The signal-to-noise ratio is defined as the ratio of the amplitude
of the output when a full-scale output is present to the amplitude of the output with no signal present. It is expressed in
decibels (dB) and measured using an A-weight filter.
GAIN LINEARITY
Gain linearity is a measure of the deviation of the actual output
amplitude from the ideal output amplitude. It is determined by
measuring the amplitude of the output signal as the amplitude
of that output signal is digitally reduced to a lower level. A perfect D/A converter exhibits no difference between the ideal and
actual amplitudes. Gain linearity is expressed in decibels (dB).
MIDSCALE ERROR
Midscale error, or bipolar zero error, is the deviation of the actual analog output from a voltage at the bias pin when the twos
complement input code representing midscale is loaded in the
DAC. Midscale error is expressed in mV.
FUNCTIONAL DESCRIPTION
The AD1866 is a complete, monolithic dual 16-bit digital audio
DAC which runs off a single +5 volt supply. As shown in the
block diagram, each channel contains a voltage reference, a
16-bit serial-to-parallel input register, a 16-bit input latch, a
16-bit DAC, and an output amplifier.
The voltage reference section provides a reference voltage and a
false ground voltage for each channel. The low noise bandgap
circuits produce reference voltages that are unaffected by
changes in temperature, time, and power supply.
The input registers are fabricated with CMOS logic gates.
These gates allow high switching speeds and low power consumption, contributing to the fast digital timing, the low glitch
and low power dissipation of the AD1866.
AD1866
V
REF
V
REF
L
V
16
B
15
V
S
V
L
14
O
13
NRL
AGND
12
11
NRR
R
V
10
O
9
V
S
CLK
DGND
VBR
V
LL
DL
DR
LR
16-BIT
1
L
2
3
4
5
6
7
8
DAC
16-BIT
SERIAL
REGISTER
16-BIT
SERIAL
REGISTER
16-BIT
DAC
AD1866 Functional Block Diagram
The 16-bit DAC uses a combination of segmentation and R-2R
architecture to achieve good integral and differential linearity.
The resistors which form the ladder structure are fabricated
with silicon-chromium thin film. Laser trimming of these resistors further reduces linearity error, resulting in low output
distortion.
The output amplifier uses both MOS and bipolar devices and
incorporates an NPN class A output stage. It is designed to produce high slew rate, low noise, low distortion, and optimal frequency response.
REV. 0
–5–
Page 6
AD1866–Analog Circuit Considerations
GROUNDING RECOMMENDATIONS
The AD1866 has two ground pins, designated as AGND (Pin
12) and DGND (Pin 7). The analog ground, AGND, serves as
the “high quality” reference ground for analog signals and as a
return path for the supply current from the analog portion of
the device. The system analog common should be located as
close as possible to Pin 12 to minimize any voltage drop which
may develop between these two points, although the internal
circuit is designed to minimize signal dependence of the analog
return current.
The digital ground, DGND, returns ground current from the
digital logic portion of the device. This pin should be connected
to the digital common node in the system. As shown in Figure
7, the analog and digital grounds should be joined at one point
in a system. When these two grounds are connected such as at
the power supply ground, care should be taken to minimize the
voltage difference between the DGND and AGND pins in order to ensure the specified performance.
POWER SUPPLIES AND DECOUPLING
The AD1866 has three power supply input pins. VS (Pins 9 and
15) provide the supply voltages which operate the analog portion of the device including the 16-bit DACs, the voltage references, and the output amplifiers. The V
supplies are designed
S
to operate from a +5 V supply. These pins should be decoupled
to the analog ground using a 0.1 µF capacitor. Good engineer-
ing practice suggests that the bypass capacitor be placed as
close as possible to the package pins. This minimizes the inherent inductive effects of printed circuit board traces.
V
(Pin 1) operates the digital portions of the chip including the
L
input shift registers and the input latching circuitry. V
is also
L
designed to operate from a +5 V supply. This pin should be bypassed to digital common using a 0.1 µF capacitor, again placed
as close as possible to the package pins. Figure 7 illustrates the
correct connection of the digital and analog supply bypass
capacitors.
An important feature of the AD1866 audio DAC is its ability to
operate at diminished power supply voltages. This feature is
very important in portable battery operated systems. As the batteries discharge, the supply voltage drops. Unlike any other audio DAC, the AD1866 can continue to function at supply
voltages as low as 3.5 V. Because of its unique design, the
power requirements of the AD1866 diminish as the battery voltage drops, further extending the operating time of the system.
POWER
SUPPLY
AD1866
V
L
1
LL
2
3
DL
CLK
4
5
DR
LR
6
DGND
7
8
VBR
(CAPACITOR VALUES ARE 0.1 µF UNLESS OTHERWISE
V
L
B
V
S
VOL
NRL
AGND
NRR
VOR
V
S
INDICATED)
16
15
14
4.7µF
+
13
12
11
10
–
4.7µF
+
–
9
Figure 7. Recommended Circuit Schematic
NOISE REDUCTION CAPACITORS
The AD1866 has two noise reduction pins, designated as NRL
(Pin 13) and NRR (Pin 11). In order to meet specifications, it
is required that external noise reduction capacitors be connected from these pins to AGND to reduce the output noise
contributed by the voltage reference circuitry. As shown in Figure 7, each of these pins should be bypassed to AGND with a
4.7 µF or larger capacitor. The connections between the ca-
pacitors, package pins and AGND should be as short as possible to achieve the lowest noise.
USING VBL AND VBR
The AD1866 has two bias voltage reference pins, designated as
V
R (Pin 8) and VBL (Pin 16). Each of these pins supplies a dc
B
reference voltage equal to the center of the output voltage swing.
These bias voltages replace “false ground” networks previously
required in single supply audio systems. At the same time, they
allow dc coupled systems, improving audio performance.
REV. 0–6–
Page 7
VOR
+5V
+5V
15
14
13
12
11
10
16
9
1
2
3
4
5
6
8
7
NRL
AGND
NRR
AD1866
LL
DL
CLK
DR
LR
DGND
V
O
L
V
O
R
V
O
R
V
S
V
B
R
VOL
V
S
V
L
VBL
VOL
Analog Circuit Considerations–AD1866
+
5V
L
V
+
5V
FALSE GROUND
(2.5V)
+
5V
O
VOR
Figure 8b. Circuitry Using Voltage Biases
Figure 8a. Schematic Using False Ground
Figure 8a illustrates the traditional approach used to generate
false ground voltages in single supply audio systems. This circuit requires additional power and circuit board space.
The AD1866 eliminates the need for “false ground” circuitry.
V
R and VBL generate the required bias voltages previously
B
generated by the “false ground.” As shown in Figure 8b, V
and V
L may be used as the reference point in each output
B
R
B
channel. This permits a dc coupled output signal path. This
eliminates ac coupling capacitors and improves low frequency
performance. It should be noted that these bias outputs have
relatively high output impedance and will not drive output currents larger than 100 µA without degrading the specified
performance.
DISTORTION PERFORMANCE AND TESTING
The THD+N figure of an audio DAC represents the amount of
undesirable signal produced during reconstruction and playback of an audio waveform. Therefore, the THD+N specification provides a direct measure to classify and choose an audio
DAC for a desired level of performance. Figure 1 illustrates the
typical THD+N versus frequency performance of the AD1866.
It is evident that the THD+N performance of the AD1866 remains stable at all three amplitude levels through a wide range
of frequencies. A load impedance of at least 2 kΩ is recommended for best THD+N performance.
Analog Devices tests all AD1866s on the basis of THD+N performance. During the distortion test, a high speed digital pattern generator transmits digital data to each channel of the
device under test. Sixteen-bit data is latched into the DAC at
352.8 kHz (8 × F
). The test input code is a digitally encoded
S
990.5 Hz sine wave with 0 dB, –20 dB, and –60 dB amplitudes.
A 4096 point FFT calculates total harmonic distortion + noise,
signal-to-noise ratio, and D-range. No deglitchers or external
adjustments are used.
REV. 0
–7–
Page 8
AD1866–Digital Circuit Considerations
CLK
M
DL
DR
LL
LR
S
B
M
S
B
Figure 9. AD1866 Control Signals
INPUT DATA
The digital input port of the AD1866 employs five signals: Data
Left (DL), Data Right (DR), Latch Left (LL), Latch Right
(LR), and Clock (CLK). DL and DR are the serial inputs for
the left and right DACs, respectively. Input data bits are clocked
into the input register on the rising edge of CLK. The falling
edges of LL and LR cause the last 16 bits which were clocked
into the serial registers to be shifted into the DACs, thereby updating the respective DAC outputs. For systems using only a
single latch signal, LL and LR may be connected together. For
systems using only one DATA signal, DR and DL may be connected together. Data is transmitted to the AD1866 in a bit
stream composed of 16-bit words with a serial, twos complement, MSB first format. Left and right channels share the Clock
(CLK) signal.
Figure 9 illustrates the general signal requirements for data
transfer for the AD1866.
TIMING
Figure 10 illustrates the specific timing requirements that must
be met in order for the data transfer to be accomplished properly. The input pins of the AD1866 are both TTL and +5 V
CMOS compatible.
L
S
B
L
S
B
>30ns
DR/DL
>10ns
CLK
>30ns
>67ns
LR/LL
>10ns
>40ns
>30ns
>40ns
>15ns
>40ns
Figure 10. AD1866 Input Signal Timing
The maximum clock rate of the AD1866 is specified to be at
least 13.5 MHz. This clock rate allows data transfer rates of 2×,
4×, 8×, and 16× F
(where FS equals 44.1 kHz). The applica-
S
tions section of this data sheet contains additional guidelines for
using the AD1866.
REV. 0–8–
Page 9
15
14
13
12
11
10
16
9
1
2
3
4
5
6
8
7
8
7
6
5
2
3
1
4
+5V POWER
SUPPLY
LEFT
CHANNEL
OUTPUT
RIGHT
CHANNEL
OUTPUT
AD1866
LL
DL
CLK
DR
LR
DGND
1
2
3
4
5
6
7
8
9
18
10
15
14
12
11
16
17
13
TEST
CXD2550P
LRCK
SLOT
DATAR
BCKO
LATCH
DATAL
LRCKO
V
DD
NRL
AGND
NRR
1000 pF
6.8kΩ
330
pF
NJM2100
1000 pF
330 pF
V
SS
V
SS
V
L
V
S
VBL
VOL
V
O
R
V
B
RV
S
+V
S
6.8kΩ
6.8kΩ
6.8kΩ
6.8kΩ
6.8kΩ
Applications of the AD1866
APPLICATIONS OF THE AD1866
The AD1866 is a high performance audio DAC specifically designed for portable and automotive digital audio applications.
These market segments have technical requirements fundamentally different than those found in the high-end or home use
market segment. Portable equipment must rely on components
which require low amounts of power to offer reasonable playback times. Also, battery voltage tends to diminish as the end of
the discharge cycle is approached. The AD1866’s ability to operate from a single +5 V supply makes it a good choice for battery operated gear. And, as the battery voltage drops, the power
dissipation of the AD1866 drops. This extends the usable battery life. Finally, as the battery supply voltage drops, the bias
voltages and signal swings also drop, preventing signal clipping
and abrupt degradation of distortion. Figure 3 illustrates how
the THD+N performance of the AD1866 remains constant
through a wide supply voltage range.
Automotive equipment relies on components which are able to
consistently perform over a wide range of temperatures. In addition, due to the limited space available in automotive applications, small size is essential. The AD1866 has guaranteed
operation between –35°C and +85°C, and the 16-pin DIP or
16-pin SOIC package is particularly attractive where overall size
is important.
Since the AD1866 provides dc bias voltages, the entire signal
chain can be dc coupled. This eliminates ac coupling capacitors
from the signal path, improving low frequency performance and
lowering system cost and size.
In summary, the AD1866 is an excellent choice for multimedia,
battery operated portable or automotive digital audio systems.
In the following sections, some examples of high performance
audio applications featuring the AD1866 are described.
AD1866 with the Sony CXD2550P Digital Filter
Figure 11 illustrates a 16-bit CD player design incorporating an
AD1866 DAC, a Sony CXD2550P digital filter, and 2-pole
antialias filters. This high performance, single supply design operates at 8× F
and is suitable for portable and automotive ap-
S
plications. In this design, the CXD2550P filter transmits left
and right channel digital data to the AD1866. The left and right
latch signals, LL and LR, are both provided by the word clock
signal (LRCKO) of the digital filter. The digital data is converted to low distortion output voltages by the output amplifiers
on the AD1866. Also, no deglitching circuitry or external adjustments are required. Bypass capacitors, noise reduction
capacitors and the antialias filter details are omitted for clarity.
ADDITIONAL APPLICATIONS
In addition to CD player designs, the AD1866 is suited for
similar applications such as DAT, portable musical instruments,
laptop and notebook personal computers, and PC audio I/O
boards. The circuit techniques illustrated here are directly applicable in those applications. Figures 12, 13, 14, and 15 show
connection diagrams for the AD1866 and several popular digital
filter chips from NPC and Yamaha. Each application operates
at 8× F
operation. Please refer to the appropriate sections of
S
this data sheet for additional information.
REV. 0
Figure 11. AD1866 with Sony CXD2550P Digital Filter
–9–
Page 10
AD1866
+5V POWER
1
2
SM5813
3
4
5
6
7
8
9
10
11
12
13
14
WCKO
BCKO
DOL
DOR
V
DD
VSS2VSS1
OW18
OW20
COB
28
27
26
25
24
23
22
21
20
19
18
17
16
15
SUPPLY
AD1866
1
V
L
2
LL
3
DL
4
CLK
5
DR
6
LR
7
DGND
RV
V
8
B
V
V
V
O
NRL
AGND
NRR
VOR
L
B
S
L
S
16
15
14
13
12
11
10
9
LOWPASS
FILTER
LOW-
PASS
FILTER
LEFT
CHANNEL
OUTPUT
RIGHT
CHANNEL
OUTPUT
1
2
3
4
5
6
7
V
8
SM5818AP
SS
V
DD
BCKO
WDCO
DOR
DOL
OMOD1
Figure 12. AD1866 with NPC SM5813 Digital Filter
+5V POWER
SUPPLY
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
AD1866
V
L
LL
DL
CLK
DR
LR
DGND
VBR
VBL
V
VOL
NRL
AGND
NRR
VOR
V
16
15
S
14
13
12
11
10
9
S
Figure 13. AD1866 with NPC SM5818AP Digital Filter
LOW
PASS
FILTER
LOW
PASS
FILTER
LEFT
CHANNEL
OUTPUT
RIGHT
CHANNEL
OUTPUT
–10–
REV. 0
Page 11
Applications–AD1866
+5V POWER
SUPPLY
YM3434
1
2
3
4
V 2
DD
5
6
7
VDD1
8
16/18
V
BCO
WCO
DRO
DLO
ST
SS
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
AD1866
V
L
LL
DL
CLK
DR
LR
DGND
V R
B
VBL
V
VOL
NRL
AGND
NRR
V
V
16
15
S
14
13
12
11
R
10
O
9
S
Figure 14. AD1866 with Yamaha YM3434 Digital Filter
LOWPASS
FILTER
LOWPASS
FILTER
LEFT
CHANNEL
OUTPUT
RIGHT
CHANNEL
OUTPUT
1
2
3
4
V
5
SS
OW20
6
7
8
9
SM5840A/B
BCKO
WCKO
DI
N
BCK
BCKO
O
VD
V
DD
D
WCK
DOL
DO
DOR
DOR
DG
+5V POWER
SUPPLY
18
17
16
15
14
13
O
12
L
11
10
10
1
2
3
4
5
6
7
8
AD1866
V
L
LL
DL
CLK
DR
LR
DGND
VBR
VBL
V
V
O
NRL
AGND
NRR
V
O
V
16
15
S
L
14
13
12
11
R
10
9
S
Figure 15. AD1866 with NPC SM5840C Digital Filter
LOWPASS
FILTER
LOWPASS
FILTER
LEFT
CHANNEL
OUTPUT
RIGHT
CHANNEL
OUTPUT
REV. 0
–11–
Page 12
AD1866
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
Plastic DIP (N) Package
16
18
0.87 (22.1) MAX
0.18
(4.57)
0.018 (0.46)
0.033 (0.84)0.1 (2.54)
9
0.25
0.31
(6.35)
(7.87)
0.035
(0.89)
0.125
(3.18)
MIN
0.011
(0.28)
0.3 (7.62)
0.18 (4.57)
MAX
Plastic SOIC (R) Package
16
0.299
(7.60)
1
0.413
(10.50)
0.012
(0.3)
0.030
(0.75)
0.013
(0.32)
0.05 (1.27)
REF
0.019 (0.49)
0.042 (1.07)
9
0.419
(10.65)
8
0.104
(2.65)
C1590–10–12/91
–12–
PRINTED IN U.S.A.
REV. 0
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