a
FUNCTIONAL BLOCK DIAGRAM
READ/CONVERT R/C
CHIP ENABLE
CE
12V/15V SUPPLY
VCC
10V REFERENCE
REF OUT
ANALOG COMMON
AC
REFERENCE INPUT
REF IN
–12V/–15V SUPPLY
VEE
BIPOLAR OFFSET
BIPOFF
10V SPAN INPUT
10VIN
20V SPAN INPUT
20VIN
28
1
MSB
N
Y
3 B
B
S L
T E
2
CONTROL
3
4
5
CLOCK
12
SAR
6
–
7
8
+
10V
REF
I DAC
9
10
11
I REF
199.95
k⍀
12
DAC
N
13
14
VOLTAGE
DIVIDER
A
T
E
COMP
–
5V SUPPLY
VLOGIC
DATA MODE SELECT
12/8
CHIP SELECT
CS
BYTE ADDRESS/
SHORT CYCLE A0
+
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 V–10 V, 0 V–20 V Input Ranges
Commercial, Industrial, and Military Temperature
Range Grades
MIL-STD-883-Compliant Versions Available
Complete 12-Bit
A/D Converters
AD674B /AD774B
VEE
O
U
T
P
U
T
B
U
F
F
E
R
S
A
26 DB10
25 DB9
24 DB8
N
Y
B
B
L
E
23 DB7
B
20 DB4
N
Y
B
B
L
E
19 DB3
C
LSB
22 DB6
21 DB5
DIGITAL
DATA
OUTPUTS
18 DB2
17 DB1
16 DB0 (LSB)
15
AD674B/AD774B
STATUS
STS
27 DB11 (MSB)
DIGITAL
COMMON DC
PRODUCT DESCRIPTION
PRODUCT HIGHLIGHTS
The AD674B and AD774B are complete 12-bit successiveapproximation 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.
1. Industry Standard Pinout: The AD674B and AD774B use
the pinout established by the industry standard AD574A.
The AD674B and AD774B are pin-compatible with the industry standard AD574A, but offer faster conversion time and busaccess speed than the AD574A and lower power consumption.
The AD674B converts in 15 µs (maximum) and the AD774B
converts in 8 µs (maximum).
The monolithic design is implemented using Analog Devices’
BiMOS II process allowing high-performance bipolar analog
circuitry 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.
Five different grades are available. The J and K grades are
specified 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-lead plastic DIP or 28-lead SOIC. All other grades
are available in a 28-lead hermetically sealed ceramic DIP.
2. Analog Operation: The precision, laser-trimmed scaling and
bipolar offset resistors provide four calibrated ranges: 0 V to
10 V and 0 V 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.
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).
4. The internal reference is trimmed to 10.00 V with 1% maximum error and 10 ppm/°C typical temperature coefficient.
The reference is available externally and can drive up to
2.0 mA beyond the requirements of the converter and bipolar offset resistors.
5. The AD674B and AD774B are available in versions compliant with MIL-STD-883. Refer to the Analog Devices Military Products Databook or current AD674B/AD774B/883B
data sheet for detailed specifications.
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 that
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
www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2002
