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
MIL-STD-883-Compliant Versions Available
FUNCTIONAL BLOCK DIAGRAM
DATA MODE SELECT
SHORT CYCLE A0
10V SPAN INPUT
20V SPAN INPUT
27 DB11 (MSB)
16 DB0 (LSB)
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.
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).
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.
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.
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% 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.
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.
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.
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