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
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
0.3" “Skinny DIP” Packaging
MIL-STD-883 Compliant Versions Available
12-Bit Ultrahigh Speed
Multiplying D/A Converter
FUNCTIONAL BLOCK DIAGRAM
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"
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
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.