12-Bit 200 kSPS
Complete Sampling ADC
a
AD678*
FUNCTIONAL BLOCK DIAGRAM
FEATURES
AC and DC Characterized and Specified
(K, B and T Grades)
12/8
SC OE EOCEN SYNC
EOC
CS
AD678
200k Conversions per Second
1 MHz Full Power Bandwidth
500 kHz Full Linear Bandwidth
72 dB S/N+D (K, B, T Grades)
Twos Complement Data Format (Bipolar Mode)
Straight Binary Data Format (Unipolar Mode)
10 M⍀ Input Impedance
CONTROL LOGIC
VOLTAGE
REF.
REF
OUT
DB11
DB2
12
REF
IN
OUTPUT
REGISTER
DB1
(R/L)
12
CONVERSION
LOGIC
12-BIT D/A
CONVERTER
DB0
(HBE)
8-Bit or 16-Bit Bus Interface
BIPOFF
V
V
V
CC
EE
DD
4
On-Board Reference and Clock
10 V Unipolar or Bipolar Input Range
Commercial, Industrial and Military Temperature
Range Grades
4-BIT FLASH
A/D
CONVERTER
GAIN
STAGE
SAMPLE/
HOLD
AIN
DGND
AGND
MIL-STD-883 Compliant Versions Available
PRODUCT DESCRIPTION
PRODUCT HIGHLIGHTS
The AD678 is a complete, multipurpose 12-bit monolithic
analog-to-digital converter, consisting of a sample-hold ampli-
fier (SHA), a microprocessor compatible bus interface, a voltage
reference and clock generation circuitry.
1. COMPLETE INTEGRATION: The AD678 minimizes ex-
ternal component requirements by combining a high speed
sample-hold amplifier (SHA), ADC, 5 V reference, clock and
digital interface on a single chip. This provides a fully speci-
fied sampling A/D function unattainable with discrete designs.
The AD678 is specified for ac (or “dynamic”) parameters such
as S/N+D ratio, THD and IMD which are important in signal
processing applications. In addition, the AD678K, B and T
grades are fully specified for dc parameters which are important
in measurement applications.
2. SPECIFICATIONS: The AD678K, B and T grades provide
fully specified and tested ac and dc parameters. The AD678J,
A and S grades are specified and tested for ac parameters; dc
accuracy specifications are shown as typicals. DC specifica-
tions (such as INL, gain and offset) are important in control
and measurement applications. AC specifications (such as
S/N+D ratio, THD and IMD) are of value in signal process-
ing applications.
The AD678 offers a choice of digital interface formats; the 12
data bits can be accessed by a 16-bit bus in a single read opera-
tion or by an 8-bit bus in two read operations (8+4), with right
or left justification. Data format is straight binary for unipolar
mode and twos complement binary for bipolar mode. The input
has a full-scale range of 10 V with a full power bandwidth of
1 MHz and a full linear bandwidth of 500 kHz. High input im-
pedance (10 MΩ) allows direct connection to unbuffered
sources without signal degradation.
3. EASE OF USE: The pinout is designed for easy board lay-
out, and the choice of single or two read cycle output pro-
vides compatibility with 16- or 8-bit buses. Factory trimming
eliminates the need for calibration modes or external trim-
ming to achieve rated performance.
This product is fabricated on Analog Devices’ BiMOS process,
combining low power CMOS logic with high precision, low
noise bipolar circuits; laser-trimmed thin-film resistors provide
high accuracy. The converter utilizes a recursive subranging
algorithm which includes error correction and flash converter
circuitry to achieve high speed and resolution.
4. RELIABILITY: The AD678 utilizes Analog Devices’ mono-
lithic BiMOS technology. This ensures long-term reliability
compared to multichip and hybrid designs.
5. UPGRADE PATH: The AD678 provides the same pinout as
the 14-bit, 128 kSPS AD679 ADC.
6. The AD678 is available in versions compliant with MIL-
STD-883. Refer to the Analog Devices Military Products
Databook or current AD678/883B data sheet for detailed
specifications.
The AD678 operates from +5 V and 12 V supplies and dissipates
560 mW (typ). The AD678 is available in 28-lead plastic DIP,
ceramic DIP, and 44-lead J-leaded ceramic surface mount packages.
Screening to MIL-STD-883C Class B is also available.
*Protected by U.S. Patent Nos. 4,804,960; 4,814,767; 4,833,345; 4,250,445;
4,808,908; RE30,586.
REV. C
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.
Tel: 781/329-4700
Fax: 781/326-8703
World Wide Web Site: http://www.analog.com
© Analog Devices, Inc., 2000
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