Complete 12-Bit
A/D Converters
a
AD674B*/AD774B*
FEATURES
FUNCTIONAL BLOCK DIAGRAM
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)
ꢂ5 V, ꢂ10 V, 0 V–10 V, 0 V–20 V Input Ranges
Commercial, Industrial, and Military Temperature
Range Grades
5V SUPPLY
STATUS
STS
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
V
LOGIC
DATA MODE SELECT
12/8
MSB
N
DB11 (MSB)
DB10
DB9
CHIP SELECT
CS
Y
B
B
L
CONTROL
3
3
BYTE ADDRESS/
4
SHORT CYCLE A
S
T
A
T
E
0
E
READ/CONVERT R/C
5
DB8
12
CLOCK
SAR
COMP
A
CHIP ENABLE
CE
6
DB7
N
Y
B
B
L
–
+
12V/15V SUPPLY
O
U
T
P
U
T
7
DB6
V
DIGITAL
DATA
OUTPUTS
CC
10V
I DAC
10V REFERENCE
REF
8
DB5
REF OUT
E
MIL-STD-883-Compliant Versions Available
ANALOG COMMON
AC
9
DB4
B
REFERENCE INPUT
N
Y
B
B
L
B
U
F
10
11
12
13
14
DB3
REF IN
I REF
–12V/–15V SUPPLY
199.95
kꢀ
+
–
DB2
F
V
EE
E
R
S
BIPOLAR OFFSET
E
DB1
BIPOFF
DAC
10V SPAN INPUT
VEE
C
N
DB0 (LSB)
10V
IN
LSB
20V SPAN INPUT
DIGITAL
COMMON DC
VOLTAGE
DIVIDER
20V
IN
AD674B/AD774B
PRODUCT DESCRIPTION
PRODUCT HIGHLIGHTS
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.
1. Industry Standard Pinout: The AD674B and AD774B use
the pinout established by the industry standard AD574A.
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.
The AD674B and AD774B are pin-compatible with the indus-
try 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
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.
4. The internal reference is trimmed to 10.00 V with 1% maxi-
mum 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 bipo-
lar offset 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.
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. C
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, norforanyinfringementsofpatentsorotherrightsofthirdpartiesthat
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
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Tel: 781/329-4700
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© Analog Devices, Inc., 2002