FUNCTIONAL BLOCK DIAGRAM

1

2

3

4

5

6

7

8

9

10

12

13

14

15

11

16

18-BIT

DAC

18-BIT

SERIAL

REGISTER

18-BIT

SERIAL

REGISTER

AD1868

LL

DL

CK

DR

LR

DGND

NRL

AGND

NRR

18-BIT

DAC

–

+

–

+

REV. A

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.

a

Single Supply

Dual 18-Bit Audio DAC

AD1868*

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 617/329-4700

Fax: 617/326-8703

FEATURES

Dual Serial Input, Voltage Output DACs

Single +5 V Supply

0.004% THD+N (typ)

Low Power: 50 mW (typ)

108 dB Channel Separation (min)

Operates at 8

Oversampling

16-Pin Plastic DIP or SOIC Package

APPLICATIONS

Portable Compact Disc Players

Portable DAT Players and Recorders

Automotive Compact Disc Players

Automotive DAT Players

Multimedia Workstations

PRODUCT DESCRIPTION

The 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. The 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.

The DACs on the AD1868 chip employ a partially segmented

architecture. The first three MSBs of each DAC are segmented

into seven elements. The 15 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 AD1868 requires no deglitcher or trimming circuitry. Low

noise is achieved through the use of two noise-reduction capacitors.

Each DAC is equipped with a high performance output ampli-

fier. 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. Reference volt-

ages of 2.5 V are provided, eliminating the need for “False

Ground” networks.

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. This allows for

operation at 2

×, 4×, 8×, or 16× the sampling frequency for each

channel. The digital input pins of the AD1868 are TTL and

+5 V CMOS compatible.

*Protected by U.S. Patent Numbers: 3,961,326; 4,141,004; 4,349,811;

4,857,862; and patents pending.

The AD1868 operates on +5 V power supplies. The digital sup-

duced digital feedthrough. Separate analog and digital ground

pins are also provided. In systems employing a single +5 volt

tery operated systems, operation will continue even with reduced

supply voltage. Typically, the AD1868 dissipates 50 mW.

The 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.

PRODUCT HIGHLIGHTS

1. Single-supply operation @ +5 V.

2. 50 mW power dissipation (typical).

3. THD+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.

9. No external adjustments required.