a
FEATURES
Complete 12-Bit A/D Converter with Reference
and Clock
8- and 16-Bit Microprocessor Bus Interface
Guaranteed Linearity Over Temperature
0 C to +70 C – AD574AJ, K, L
–55 C to +125 C – AD574AS, T, U
No Missing Codes Over Temperature
35 s Maximum Conversion Time
Buried Zener Reference for Long-Term Stability
and Low Gain T.C. 10 ppm/ C max AD574AL
12.5 ppm/ C max AD574AU
Ceramic DIP, Plastic DIP or PLCC Package
Available in Higher Speed, Pinout-Compatible Versions
(15 s AD674B, 80 s AD774B; 10 s (with SHA) AD1674)
Available in Versions Compliant with MIL-STD-883 and
JAN QPL
+5V SUPPLY
V
LOGIC
DATA MODE SELECT
12/8
CHIP SELECT
CS
BYTE ADDRESS/
SHORT CYCLE
A
O
READ/CONVERT
R/C
CHIP ENABLE
CE
+12/+15V SUPPLY
V
CC
+10V REFERENCE
REF OUT
ANALOG COMMON
AC
REFERENCE INPUT
REF IN
-12/-15V SUPPLY
V
EE
BIPOLAR OFFSET
BIP OFF
10V SPAN INPUT
10V
IN
1
2
3
4
5
6
7
Complete
12-Bit A/D Converter
AD574A*
BLOCK DIAGRAM AND
PIN CONFIGURATION
STATUS
STS
DB11
27
MSB
26 DB10
25 DB9
24 DB8
23 DB7
22 DB6
21 DB5
20 DB4
19 DB3
18 DB2
17 DB1
DB0
16 LSB
15 DIGITAL COMMON
DC
DIGITAL
DATA
OUTPUTS
28
MSB
CONTROL
3
S
T
A
T
E
O
U
T
P
U
T
B
U
F
F
E
R
S
CLOCK
3k
SAR
12
N
I
B
B
L
E
A
N
I
B
B
L
E
B
N
I
B
B
L
E
C
LSB
COMP 12
8
9
10
19.95k
11
12
13
5k
9.95k
5k
DAC N
V
EE
10V
REF
I
DAC
I
DAC
=
4 x N x I
REF
I
REF
8k
20V SPAN INPUT 14
20V
IN
AD574A
12
PRODUCT DESCRIPTION
PRODUCT HIGHLIGHTS
The AD574A is a complete 12-bit successive-approximation
analog-to-digital converter with 3-state output buffer circuitry
for direct interface to an 8- or 16-bit microprocessor bus. A high
precision voltage reference and clock are included on-chip, and
the circuit guarantees full-rated performance without external
circuitry or clock signals.
The AD574A design is implemented using Analog Devices’
Bipolar/I
2
L process, and integrates all analog and digital func-
tions on one chip. Offset, linearity and scaling errors are mini-
mized by active laser-trimming of thin-film resistors at the wafer
stage. The voltage reference uses an implanted buried Zener for
low noise and low drift. On the digital side, I
2
L logic is used for
the successive-approximation register, control circuitry and
3-state output buffers.
The AD574A is available in six different grades. The AD574AJ,
K, and L grades are specified for operation over the 0°C to
+70°C temperature range. The AD574AS, T, and U are speci-
fied for the –55°C to +125°C range. All grades are available in a
28-pin hermetically-sealed ceramic DIP. Also, the J, K, and L
grades are available in a 28-pin plastic DIP and PLCC, and the
J and K grades are available in ceramic LCC.
The S, T, and U grades in ceramic DIP or LCC are available
with optional processing to MIL-STD-883C Class B; the T
and U grades are available as JAN QPL. The Analog Devices’
Military Products Databook should be consulted for details on
/883B testing of the AD574A.
*Protected
by U.S. Patent Nos. 3,803,590; 4,213,806; 4,511,413; RE 28,633
.
1. The AD574A interfaces to most 8- or 16-bit microproces-
sors. Multiple-mode three-state output buffers connect di-
rectly to the data bus while the read and convert commands
are taken from the control bus. 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).
2. The precision, laser-trimmed scaling and bipolar offset resis-
tors provide four calibrated ranges: 0 volts to +10 volts and 0
volts to +20 volts unipolar, –5 volts to +5 volts and –10 volts
to +10 volts bipolar. Typical bipolar offset and full-scale cali-
bration errors of
±
0.1% can be trimmed to zero with one ex-
ternal component each.
3. The internal buried Zener reference is trimmed to 10.00
volts with 0.2% maximum error and 15 ppm/°C typical T.C.
The reference is available externally and can drive up to
1.5 mA beyond the requirements of the reference and bipolar
offset resistors.
4. AD674B (15
µs)
and AD774B (8
µs)
provide higher speed,
pin compatibility; AD1674 (10
µs)
includes on-chip Sample-
Hold Amplifier (SHA).
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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