Single Supply
Dual 18-Bit Audio DAC
a
AD1868*
FUNCTIO NAL BLO CK D IAGRAM
FEATURES
Dual Serial Input, Voltage Output DACs
Single +5 V Supply
0.004% THD+N (typ)
AD1868
18-BIT
DAC
V
V
L
L
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
B
Low Pow er: 50 m W (typ)
108 dB Channel Separation (m in)
Operates at 8؋
Oversam pling
16-Pin Plastic DIP or SOIC Package
–
+
V
18-BIT
SERIAL
REGISTER
LL
DL
S
V
L
O
V
APPLICATIONS
REF
NRL
CK
Portable Com pact Disc Players
Portable DAT Players and Recorders
Autom otive Com pact Disc Players
Autom otive DAT Players
AGND
NRR
DR
18-BIT
SERIAL
REGISTER
V
REF
LR
Multim edia Workstations
+
–
V
R
DGND
O
18-BIT
DAC
V
V
R
S
B
P RO D UCT D ESCRIP TIO N
T he AD1868 is a complete dual 18-bit DAC offering excellent
performance while requiring a single +5 V power supply. It is
fabricated on Analog Devices’ ABCMOS wafer fabrication pro-
cess. T he monolithic chip includes CMOS logic elements, bipo-
lar and MOS linear elements, and laser-trimmed thin-film
resistor elements. Careful design and layout techniques have re-
sulted in low distortion, low noise, high channel separation, and
low power dissipation.
T he AD1868 operates on +5 V power supplies. T he digital sup-
ply, VL, can be separated from the analog supply, VS, for re-
duced digital feedthrough. Separate analog and digital ground
pins are also provided. In systems employing a single +5 volt
power supply, VL and VS should be connected together. In bat-
tery operated systems, operation will continue even with reduced
supply voltage. T ypically, the AD1868 dissipates 50 mW.
T he DACs on the AD1868 chip employ a partially segmented
architecture. T he first three MSBs of each DAC are segmented
into seven elements. T he 15 LSBs are produced using standard
R-2R techniques. T he segments and R-2R resistors are laser
trimmed to provide extremely low total harmonic distortion.
T he AD1868 requires no deglitcher or trimming circuitry. Low
noise is achieved through the use of two noise-reduction capacitors.
T he AD1868 is packaged in either a 16-pin plastic DIP or a 16-
pin plastic SOIC package. Operation is guaranteed over the tem-
perature range of –35°C to +85°C and over the voltage supply
range of 4.75 V to 5.25 V.
P RO D UCT H IGH LIGH TS
1. Single-supply operation @ +5 V.
Each DAC is equipped with a high performance output ampli-
fier. T hese amplifiers achieve fast settling and high slew rate,
producing ±1 V signals at load currents up to ±1 mA. T he
buffered output signal range is 1.5 V to 3.5 V. Reference volt-
ages of 2.5 V are provided, eliminating the need for “False
Ground” networks.
2. 50 mW power dissipation (typical).
3. T HD+N is 0.004% (typical).
4. Signal-to-Noise Ratio is 97.5 dB (typical).
5. 108 dB channel separation (minimum).
6. Compatible with all digital filter chips.
7. 16-pin DIP and 16-pin SOIC packages.
8. No deglitcher required.
A versatile digital interface allows the AD1868 to be directly
connected to all digital filter chips. Fast CMOS logic elements
allow for an input clock rate of up to 13.5 MHz. T his allows for
operation at 2×, 4×, 8×, or 16× the sampling frequency for each
channel. T he digital input pins of the AD1868 are T T L and
+5 V CMOS compatible.
9. No external adjustments required.
*P r otected by U.S. P atent Num ber s: 3,961,326; 4,141,004; 4,349,811;
4,857,862; and patents pending.
REV. A
Inform ation furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assum ed by Analog Devices for its
use, nor for any infringem ents of patents or other rights of third parties
which m ay result from its use. No license is granted by im plication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norw ood, MA 02062-9106, U.S.A.
Tel: 617/ 329-4700
Fax: 617/ 326-8703