a
FEATURES
30 MSPS Update Rate
16-Bit Resolution
Linearity: 1/2 LSB DNL @ 14 Bits
1 LSB INL @ 14 Bits
Fast Settling: 25 ns Full-Scale Settling to 0.025%
SFDR @ 1 MHz Output: 86 dBc
THD @ 1 MHz Output: 71 dBc
Low Glitch Impulse: 35 pV-s
Power Dissipation: 465 mW
On-Chip 2.5 V Reference
Edge-Triggered Latches
Multiplying Reference Capability
APPLICATIONS
Arbitrary Waveform Generation
Communications Waveform Reconstruction
Vector Stroke Display
PRODUCT DESCRIPTION
The AD768 is a 16-bit, high speed digital-to-analog converter
(DAC) that offers exceptional ac and dc performance. The
AD768 is manufactured on ADI’s Advanced Bipolar CMOS
(ABCMOS) process, combining the speed of bipolar transistors,
the accuracy of laser-trimmable thin film resistors, and the efficiency of CMOS logic. A segmented current source architecture
is combined with a proprietary switching technique to reduce
glitch energy and maximize dynamic accuracy. Edge triggered
input latches and a temperature compensated bandgap reference
have been integrated to provide a complete monolithic DAC
solution.
The AD768 is a current-output DAC with a nominal full-scale
output current of 20 mA and a 1 kΩ output impedance. Differential current outputs are provided to support single-ended
or differential applications. The current outputs may be tied
directly to an output resistor to provide a voltage output, or fed
to the summing junction of a high speed amplifier to provide a
buffered voltage output. Also, the differential outputs may be
interfaced to a transformer or differential amplifier.
The on-chip reference and control amplifier are configured for
maximum accuracy and flexibility. The AD768 can be driven by
the on-chip reference or by a variety of external reference voltages based on the selection of an external resistor. An external
capacitor allows the user to optimally trade off reference bandwidth and noise performance.
16-Bit, 30 MSPS
D/A Converter
AD768
FUNCTIONAL BLOCK DIAGRAM
VDD
DCOM
(MSB)
DB15
AD768
MSBs: SEGMENTED
CURRENT SOURCES
AND SWITCHES
MSB
DECODER
AND
EDGETRIGGERED
BIT
LATCHES
IOUTA
LSBs:
CURRENT SOURCES,
SWITCHES, AND
1kΩ R-2R
LADDERS
IOUTB
1k
1k
LADCOM
2.5V
BANDGAP
REFERENCE
DB0
(LSB)
CLOCK
NC
CONTROL
AMP
REFCOM REFOUT
IREFIN
VEE
NR
PRODUCT HIGHLIGHTS
1. The low glitch and fast settling time provide outstanding
dynamic performance for waveform reconstruction or digital
synthesis requirements, including communications.
2. The excellent dc accuracy of the AD768 makes it suitable for
high speed A/D conversion applications.
3. On-chip, edge-triggered input CMOS latches interface
readily to CMOS logic families. The AD768 can support update rates up to 40 MSPS.
4. A temperature compensated, 2.5 V bandgap reference is
included on-chip allowing for generation of the reference
input current with the use of a single external resistor. An external reference may also be used.
5. The current output(s) of the AD768 may be used singly or
differentially, either into a load resistor, external op amp
summing junction or transformer.
6. Proper selection of an external resistor and compensation
capacitor allow the performance-conscious user to optimize
the AD768 reference level and bandwidth for the target
application.
The AD768 operates on ± 5 V supplies, typically consuming
465 mW of power. The AD768 is available in a 28-pin SOIC
package and is specified for operation over the industrial temperature range.
REV. B
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.
© Analog Devices, Inc., 1996
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
