Complete Dual 18-Bit
16 ؋ FS Audio DAC
Dual Serial Input, Voltage Output DACs
No External Components Required
110 dB SNR
Operates at 16 ؋ Oversampling per Channel
؎5 Volt Operation
116 dB Channel Separation
Pin Compatible with AD1864
DIP or SOIC Packaging
Multichannel Audio Applications
Compact Disc Players
Multivoice Keyboard Instruments
DAT Players and Recorders
Digital Mixing Consoles
The AD1865 is a complete, dual 18-bit DAC offering excellent
THD+N and SNR while requiring no external components. Two
complete signal channels are included. This results in cophased
voltage or current output signals and eliminates the need for
output demultiplexing circuitry. The monolithic AD1865 chip
includes CMOS logic elements, bipolar and MOS linear ele-
ments and laser-trimmed thin-film resistor elements, all fabri-
cated on Analog Devices’ ABCMOS process.
The DACs on the AD1865 chip employ a partially segmented
architecture. The first four MSBs of each DAC are segmented
into 15 elements. The 14 LSBs are produced using standard R-2R
techniques. Segment and R-2R resistors are laser trimmed to pro-
vide extremely low total harmonic distortion. This architecture
minimizes errors at major code transitions resulting in low out-
put glitch and eliminating the need for an external deglitcher.
When used in the current output mode, the AD1865 provides
two ± 1 mA output signals.
Each channel is equipped with a high performance output am-
plifier. These amplifiers achieve fast settling and high slew rate,
producing ± 3 V signals at load currents up to 8 mA. Each out-
put amplifier is short-circuit protected and can withstand indefi-
nite short circuits to ground.
The AD1865 was designed to balance two sets of opposing re-
quirements, channel separation and DAC matching. High chan-
nel separation is the result of careful layout. At the same time,
both channels of the AD1865 have been designed to ensure
matched gain and linearity as well as tracking over time and
temperature. This assures optimum performance when used in
stereo and multi-DAC per channel applications.
*Protected by U.S. Patents Nos.: RE 30,586; 3,961,326; 4,141,004;
4,349,811; 4,855,618; 4,857,862.
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.
FUNCTIONAL BLOCK DIAGRAM
NC = NO CONNECT
A versatile digital interface allows the AD1865 to be directly
connected to standard digital filter chips. This interface employs
five signals: Data Left (DL), Data Right (DR), Latch Left (LL),
Latch Right (LR) and Clock (CLK). DL and DR are the serial
input pins for the left and right DAC input registers. Input data
bits are clocked into the input register on the rising edge of
CLK. A low-going latch edge updates the respective DAC out-
put. 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.
The AD1865 operates with ± 5 V power supplies. The digital
supply, VL, can be separated from the analog supplies, VS and
–VS, for reduced digital feedthrough. Separate analog and digital
ground pins are also provided. The AD1865 typically dissipates
only 225 mW, with a maximum power dissipation of 260 mW.
The AD1865 is packaged in both a 24-pin plastic DIP and a
28-pin SOIC package. Operation is guaranteed over the temper-
ature range of –25°C to +70°C and over the voltage supply
range of ± 4.75 V to ± 5.25 V.
11. The AD1865 is a complete dual 18-bit audio DAC.
12. 110 dB signal-to-noise ratio for low noise operation.
13. THD+N is typically 0.003%.
14. Interchannel gain and midscale matching.
15. Output voltages and currents are cophased.
16. Low glitch for improved sound quality.
17. Both channels are 100% tested at 16 × FS.
18. Low Power—only 225 mW typ, 260 mW max.
19. Five-wire interface for individual DAC control.
10. 24-pin DIP or 28-pin SOIC packages available.
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