FUNCTIONAL BLOCK DIAGRAM

REV. A

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a

12-Bit Ultrahigh Speed

Multiplying D/A Converter

AD668

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

Tel: 617/329-4700

Fax: 617/326-8703

FEATURES

Ultrahigh Speed: Current Settling to 1 LSB in 90 ns for

a Full-Scale Change in Digital Input. Voltage Settling

to 1 LSB in 120 ns for a Full-Scale Change in Analog

Input

15 MHz Reference Bandwidth

Monotonicity Guaranteed over Temperature

10.24 mA Current Output or 1.024 V Voltage Output

Integral and Differential Linearity Guaranteed over

Temperature

0.3" “Skinny DIP” Packaging

MIL-STD-883 Compliant Versions Available

PRODUCT DESCRIPTION

The AD668 is an ultrahigh speed, 12-bit, multiplying digital-to-

analog converter, providing outstanding accuracy and speed per-

formance in responding to both analog and digital inputs. The

AD668 provides a level of performance and functionality in a

monolithic device that exceeds that of many contemporary hy-

brid devices. The part is fabricated using Analog Devices’

Complementary Bipolar (CB) Process, which features vertical

NPN and PNP devices on the same chip without the use of

dielectric isolation. The AD668’s design capitalizes on this pro-

prietary process in combination with standard low impedance

circuit techniques to provide its unique combination of speed

and accuracy in a monolithic part.

The wideband reference input is buffered by a high gain, closed

loop reference amplifier. The reference input is essentially a 1 V,

high impedance input, but trimmed resistive dividers are pro-

vided to readily accommodate 5 V and 1.25 V references. The

reference amplifier features an effective small signal bandwidth

of 15 MHz and an effective slew rate of 3% of full scale/ns.

Multiple matched current sources and thin film ladder tech-

niques are combined to produce bit weighting. The output range

can nominally be taken as a 10.24 mA current output or a 1.024 V

voltage output. Varying the analog input can provide modulation

of the DAC full scale from 10% to 120% of its nominal value.

Bipolar outputs can be realized through pin-strapping to provide

two-quadrant operation without additional external circuitry.

Laser wafer trimming insures full 12-bit linearity and excellent

gain accuracy. All grades of the AD668 are guaranteed mono-

tonic over their full operating temperature range. Furthermore,

the output resistance of the DAC is trimmed to 100

Ω ± 1.0%.

The AD668 is available in four performance grades. The

AD668JQ and KQ are specified for operation from 0

°C to

+70

°C, the AD668AQ is specified for operation from –40°C to

+85

°C, and the AD668SQ specified for operation from –55°C

to +125

°C. All grades are available in a 24-pin cerdip (0.3"

package.

PRODUCT HIGHLIGHTS

1. The fast settling time of the AD668 provides suitable perfor-

mance for waveform generation, graphics display, and high

speed A/D conversion applications.

2. The high bandwidth reference channel allows high frequency

modulation between analog and digital inputs.

3. The AD668’s design is configured to allow wide variation of

the analog input, from 10% to 120% of its nominal value.

4. The AD668’s combination of high performance and tremen-

dous flexibility makes it an ideal building block for a variety

of high speed, high accuracy instrumentation applications.

5. The digital inputs are readily compatible with both TTL and

5 V CMOS logic families.

6. Skinny DIP (0.3") packaging minimizes board space require-

ments and eases layout considerations.

7. The AD668 is available in versions compliant with MIL-

STD-883. Refer to the Analog Devices Military Products

Databook or current AD668/883B data sheet for detailed

specifications.