FUNCTIONAL BLOCK DIAGRAM
REV. A
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a
Low Cost Signal
Conditioning 8-Bit ADC
AD670
FEATURES
Complete 8-Bit Signal Conditioning A/D Converter
Including Instrumentation Amp and Reference
Microprocessor Bus Interface
10 ms Conversion Speed
Flexible Input Stage: Instrumentation Amp Front End
Provides Differential Inputs and High Common-Mode
Rejection
No User Trims Required
No Missing Codes Over Temperature
Single +5 V Supply Operation
Convenient Input Ranges
20-Pin DIP or Surface-Mount Package
Low Cost Monolithic Construction
MIL-STD-883B Compliant Versions Available
GENERAL DESCRIPTION
The AD670 is a complete 8-bit signal conditioning analog-
to-digital converter. It consists of an instrumentation amplifier
front end along with a DAC, comparator, successive approxima-
tion register (SAR), precision voltage reference, and a three-
state output buffer on a single monolithic chip. No external
components or user trims are required to interface, with full
accuracy, an analog system to an 8-bit data bus. The AD670
will operate on the +5 V system supply. The input stage pro-
vides differential inputs with excellent common-mode rejection
and allows direct interface to a variety of transducers.
The device is configured with input scaling resistors to permit
two input ranges: 0 mV to 255 mV (1 mV/LSB) and 0 to 2.55 V
(10 mV/LSB). The AD670 can be configured for both unipolar
and bipolar inputs over these ranges. The differential inputs and
common-mode rejection of this front end are useful in applica-
tions such as conversion of transducer signals superimposed on
common-mode voltages.
The AD670 incorporates advanced circuit design and proven
processing technology. The successive approximation function
is implemented with I
2
L (integrated injection logic). Thin-film
SiCr resistors provide the stability required to prevent missing
codes over the entire operating temperature range while laser
wafer trimming of the resistor ladder permits calibration of the
device to within ±1 LSB. Thus, no user trims for gain or offset
are required. Conversion time of the device is 10 µs.
The AD670 is available in four package types and five grades.
The J and K grades are specified over 0°C to +70°C and come
in 20-pin plastic DIP packages or 20-terminal PLCC packages.
The A and B grades (–40°C to +85°C) and the S grade (–55°C
to +125°C) come in 20-pin ceramic DIP packages.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700 Fax: 617/326-8703
The S grade is also available with optional processing to
MIL-STD-883 in 20-pin ceramic DIP or 20-terminal LCC
packages. The Analog Devices Military Products Databook
should be consulted for detailed specifications.
PRODUCT HIGHLIGHTS
1. The AD670 is a complete 8-bit A/D including three-state
outputs and microprocessor control for direct connection to
8-bit data buses. No external components are required to
perform a conversion.
2. The flexible input stage features a differential instrumenta-
tion amp input with excellent common-mode rejection. This
allows direct interface to a variety of transducers without
preamplification.
3. No user trims are required for 8-bit accurate performance.
4. Operation from a single +5 V supply allows the AD670 to
run off of the microprocessor’s supply.
5. Four convenient input ranges (two unipolar and two bipolar)
are available through internal scaling resistors: 0 mV to
255 mV (1 mV/LSB) and 0 V to 2.55 V (10 mV/LSB).
6. Software control of the output mode is provided. The user
can easily select unipolar or bipolar inputs and binary or 2s
complement output codes.
