Complete
12-Bit A/D Converter
a
AD574A*
BLOCK DIAGRAM AND
PIN CONFIGURATION
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
STATUS
STS
+5V SUPPLY
VLOGIC
1
2
28
DB11
MSB
DATA MODE SELECT
12/8
MSB
27
26
25
24
23
22
21
20
19
18
N
I
B
B
L
E
CONTROL
CHIP SELECT
CS
BYTE ADDRESS/
SHORT CYCLE
AO
3
DB10
DB9
DB8
DB7
DB6
DB5
DB4
DB3
DB2
–55؇C to +125؇C – AD574AS, T, U
3
4
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
S
T
A
T
E
READ/CONVERT
A
5
SAR
CLOCK
3k
12
R/C
CHIP ENABLE
CE
6
N
I
B
B
L
E
O
U
T
P
U
T
+12/+15V SUPPLY
VCC
7
DIGITAL
DATA
OUTPUTS
12
COMP
IDAC
IDAC
4 x N x IREF
+10V REFERENCE
REF OUT
8
10V
REF
B
=
ANALOG COMMON
AC
9
B
U
F
REFERENCE INPUT
REF IN
-12/-15V SUPPLY
VEE
N
I
B
B
L
E
10
11
12
13
14
8k
IREF
19.95k
9.95k
5k
5k
F
E
R
S
BIPOLAR OFFSET
BIP OFF
17 DB1
DB0
C
LSB
DAC
N
VEE
10V SPAN INPUT
10VIN
16
LSB
DIGITAL COMMON
DC
20V SPAN INPUT
20VIN
15
12
AD574A
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.
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).
The AD574A design is implemented using Analog Devices’
Bipolar/I2L 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, I2L logic is used for
the successive-approximation register, control circuitry and
3-state output buffers.
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.
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.
4. AD674B (15 µs) and AD774B (8 µs) provide higher speed,
pin compatibility; AD1674 (10 µs) includes on-chip Sample-
Hold Amplifier (SHA).
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.
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.
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Tel: 617/329-4700
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