12-Bit A/D Converter
Complete 12-Bit A/D Converter with Reference
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
BLOCK DIAGRAM AND
DATA MODE SELECT 2
12 A A 24 DB8
4 x N x IREF
REFERENCE INPUT 10
10V SPAN INPUT
20V SPAN INPUT
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/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.
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 .
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.
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
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
4. AD674B (15 µs) and AD774B (8 µs) provide higher speed,
pin compatibility; AD1674 (10 µs) includes on-chip Sample-
Hold Amplifier (SHA).
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