Complete
12-Bit A/D Converters
a
AD674B*/AD774B*
FUNCTIONAL BLOCK DIAGRAM
FEATURES
Complete Monolithic 12-Bit A/D Converters with
Reference, Clock, and Three-State Output Buffers
Industry Standard Pinout
High Speed Upgrades for AD574A
8- and 16-Bit Microprocessor Interface
8 s (max) Conversion Time (AD774B)
15 s (max) Conversion Time (AD674B)
؎5 V, ؎10 V, 0-10 V, 0-20 V Input Ranges
Commercial, Industrial and Military Temperature
Range Grades
+5V SUPPLY
STATUS
STS
1
28
27
26
25
24
23
22
V
LOGIC
MSB
DATA MODE SELECT
12/8
DB11 (MSB)
2
3
N
3
Y
B
B
L
CHIP SELECT
CS
CONTROL
DB10
S
T
A
T
E
BYTE ADDRESS/
SHORT CYCLE
DB9
DB8
E
4
5
A
0
READ/ CONVERT
R/C
A
12
12
SAR
COMP
CLOCK
O
U
T
P
U
T
CHIP ENABLE
CE
DB7
DB6
6
7
N
Y
B
B
L
+12/+15V SUPPLY
DIGITAL
DATA
OUTPUTS
V
CC
I DAC
+10V REFERENCE
REF OUT
B
U
F
10V
REF
DB5
DB4
8
9
21
20
E
MIL-STD-883 Compliant Versions Available
B
ANALOG COMMON
AC
F
E
R
S
REF
I
REFERENCE INPUT
REF IN
N
Y
B
B
L
DB3
DB2
10
11
12
19
18
17
16
15
19.95k
_
_
12/ 15V SUPPLY
V
EE
BIPOLAR OFFSET
BIPOFF
E
DAC
V
EE
DB1
N
C
10V SPAN INPUT
DB0 (LSB)
13
14
12
VOLTAGE
DIVIDER
10V
LSB
IN
20V SPAN INPUT
DIGITAL COMMON DC
20V
AD674B/AD774B
IN
PRODUCT HIGHLIGHTS
PRODUCT DESCRIPTION
1. Industry Standard Pinout: The AD674B and AD774B utilize
the pinout established by the industry standard AD574A.
The AD674B and AD774B are complete 12-bit successive-
approximation analog-to-digital converters with three-state
output buffer circuitry for direct interface to 8- and 16-bit
microprocessor busses. A high precision voltage reference and
clock are included on chip, and the circuit requires only power
supplies and control signals for operation.
2. Analog Operation: The precision, laser-trimmed scaling and
bipolar offset resistors provide four calibrated ranges: 0 to
+10 V and 0 to +20 V unipolar; –5 V to +5 V and –10 V to
+10 V bipolar. The AD674B and AD774B operate on +5 V
and ±12 V or ±15 V power supplies.
The AD674B and AD774B are pin compatible with the industry
standard AD574A, but offer faster conversion time and bus-
access speed than the AD574A and lower power consumption.
The AD674B converts in 15 µs (maximum) and the AD774B
converts in 8 µs (maximum).
3. Flexible Digital Interface: On-chip multiple-mode three-state
output buffers and interface logic allow direct connection to
most microprocessors. The 12 bits of output data can be
read either as one 12-bit word or as two 8-bit bytes (one with
8 data bits, the other with 4 data bits and 4 trailing zeros).
The monolithic design is implemented using Analog Devices’
BiMOS II process allowing high performance bipolar analog cir-
cuitry to be combined on the same die with digital CMOS logic.
Offset, linearity and scaling errors are minimized by active laser-
trimming of thin-film resistors.
4. The internal reference is trimmed to 10.00 volts with 1%
maximum error and 10 ppm/°C typical temperature coeffi-
cient. The reference is available externally and can drive up
to 2.0 mA beyond the requirements of the converter and bi-
polar offset resistors.
Five different grades are available. The J and K grades are speci-
fied for operation over the 0°C to +70°C temperature range.
The A and B grades are specified from –40°C to +85°C, the T
grade is specified from –55°C to +125°C. The J and K grades
are available in a 28-pin plastic DIP or 28-lead SOIC. All other
grades are available in a 28-pin hermetically sealed ceramic
DIP.
5. The AD674B and AD774B are available in versions compli-
ant with MIL-STD-883. Refer to the Analog Devices Mili-
tary Products Databook or current AD674B/AD774B/883B
data sheet for detailed specifications.
*Protected by U.S. Patent Nos. 4,250,445; 4,808,908; RE30586.
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
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