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
Low Cost Signal
Conditioning 8-Bit ADC
AD670
FUNCTIONAL BLOCK DIAGRAM
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.
REV. A
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.
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
AD670–SPECIFICATIONS
Model
OPERATING TEMPERATURE RANGE
RESOLUTION
CONVERSION TIME
RELATIVE ACCURACY
T
MIN
to T
MAX
DIFFERENTIAL LINEARITY ERROR
1
T
MIN
to T
MAX
GAIN ACCURACY
@ +25°C
T
MIN
to T
MAX
UNIPOLAR ZERO ERROR
@ +25°C
T
MIN
to T
MAX
BIPOLAR ZERO ERROR
@ +25°C
T
MIN
to T
MAX
ANALOG INPUT RANGES
DIFFERENTIAL (–V
IN
to +V
IN
)
Low Range
High Range
ABSOLUTE (Inputs to Power GND)
Low Range T
MIN
to T
MAX
High Range T
MIN
to T
MAX
BIAS CURRENT (255 mV RANGE)
T
MIN
to T
MAX
OFFSET CURRENT (255 mV RANGE)
T
MIN
to T
MAX
2.55 V RANGE INPUT RESISTANCE
2.55 V RANGE FULL-SCALE MATCH
+ AND – INPUT
COMMON-MODE REJECTION
RATIO (255 mV RANGE)
COMMON-MODE REJECTION
RATIO (2.55 V RANGE)
POWER SUPPLY
Operating Range
Current I
CC
Rejection Ratio T
MIN
to T
MAX
DIGITAL OUTPUTS
SINK CURRENT (V
OUT
= 0.4 V)
T
MIN
to T
MAX
SOURCE CURRENT (V
OUT
= 2.4 V)
T
MIN
to T
MAX
THREE-STATE LEAKAGE CURRENT
OUTPUT CAPACITANCE
DIGITAL INPUT VOLTAGE
V
INL
V
INH
DIGITAL INPUT CURRENT
(0
≤
V
IN
≤
+5 V)
I
INL
I
INH
INPUT CAPACITANCE
NOTES
1
Tested at V
CC
= 4 5 V, 5.0 V and 5.5 V.
(@ V
CC
= +5 V and +25 C, unless otherwise noted)
Min
0
8
10
1/2
l/2
GUARANTEED NO MISSING CODES ALL GRADES
1.5
2.0
1.5
2.0
1.5
2.0
0.75
1.0
0.75
1.0
0.75
1.0
LSB
LSB
LSB
LSB
LSB
LSB
AD670J
Typ
Max
+70
Min
0
8
AD670K
Typ
Max
+70
10
1/4
1/2
Units
°C
Bit
µs
LSB
LSB
0 to +255
–128 to +127
0 to +2.55
–1.28 to +1.27
–0.150
–1.50
200
40
8.0
±
1/2
1
1
4.5
30
5.5
45
0.015
4.5
V
CC
– 3.4
V
CC
500
200
12.0
8.0
–0.150
–1.50
0 to +255
–128 to +127
0 to +2.55
–1.28 to +1.27
V
CC
– 3.4
V
CC
200
40
500
200
12.0
±
1/2
1
1
5.5
45
0.015
mV
mV
V
V
V
V
nA
nA
kΩ
LSB
LSB
LSB
V
mA
% of FS/%
30
1.6
0.5
40
5
0.8
2.0
1.6
0.5
40
5
0.8
2.0
mA
mA
µA
pF
V
V
–100
+100
10
–100
+100
10
µA
µA
pF
Specifications shown in
boldface
are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels. All min and max specifications
are guaranteed although only those shown in boldface are tested on all production units.
Specifications subject to change without notice.
–2–
REV. A
AD670
Model
Min
OPERATING TEMPERATURE RANGE
RESOLUTION
CONVERSION TIME
RELATIVE ACCURACY
T
MIN
to T
MAX
DIFFERENTIAL LINEARITY ERROR
1
T
MIN
to T
MAX
GAIN ACCURACY
@ +25°C
T
MIN
to T
MAX
UNIPOLAR ZERO ERROR
@ +25°C
T
MIN
to T
MAX
BIPOLAR ZERO ERROR
@ +25°C
T
MIN
to T
MAX
ANALOG INPUT RANGES
DIFFERENTIAL ( –V
IN
to +V
IN
)
Low Range
High Range
ABSOLUTE (Inputs to Power GND)
Low Range T
MIN
to T
MAX
High Range T
MIN
to T
MAX
BIAS CURRENT (255 mV RANGE)
T
MIN
to T
MAX
OFFSET CURRENT (255 mV RANGE)
T
MIN
to T
MAX
2.55 V RANGE INPUT RESISTANCE
2.55 V RANGE FULL-SCALE MATCH
+ AND – INPUT
COMMON-MODE REJECTION
RATIO (255 mV RANGE)
COMMON-MODE REJECTION
RATIO (2.55 V RANGE)
POWER SUPPLY
Operating Range
Current I
CC
Rejection Ratio T
MIN
to T
MAX
DIGITAL OUTPUTS
SINK CURRENT (V
OUT
= 0.4 V)
T
MIN
to T
MAX
SOURCE CURRENT (V
OUT
= 2.4 V)
T
MIN
to T
MAX
THREE-STATE LEAKAGE CURRENT
OUTPUT CAPACITANCE
DIGITAL INPUT VOLTAGE
V
INL
V
INH
DIGITAL INPUT CURRENT
(0
≤
V
IN
≤
+5 V)
I
INL
I
INH
INPUT CAPACITANCE
5
0.8
2.0
2.0
4.5
30
8.0
±
1/2
1
1
5.5
45
0.015
4.5
30
–40
8
10
1/2
1/2
AD670A
Typ
Max
+85
Min
–40
AD670B
Typ
Max
+85
8
10
1/4
1/2
Min
–55
AD670S
Typ
Max
+125
8
10
1/2
1
Units
°C
Bit
µs
LSB
LSB
GUARANTEED NO MISSING CODES ALL GRADES
1.5
2.5
1.0
2.0
1.0
2.0
0.75
1.5
0.5
1.0
0.5
1.0
1.5
2.5
1.0
2.0
1.0
2.0
LSB
LSB
LSB
LSB
LSB
LSB
0 to +255
–128 to +127
0 to +2.55
–1.28 to +1.27
–0.150
–1.50
200
40
V
CC
– 3.5 –0.150
V
CC
–1.50
500
200
12.0
8.0
0 to +255
–128 to +127
0 to +2.55
–1.28 to +1.27
V
CC
– 3.5 –0.150
V
CC
–1.50
200
40
500
200
12.0
±
1/2
1
1
5.5
45
0.015
4.75
8.0
0 to +255
–128 to +127
0 to +2.55
–1.28 to +1.27
mV
mV
V
V
V
CC
– 3.5
V
V
CC
V
200
40
750
200
12.0
±
1/2
1
1
5.5
45
0.015
nA
nA
kΩ
LSB
LSB
LSB
V
mA
% of FS/%
30
1.6
0.5
40
1.6
0.5
40
5
0.8
1.6
0.5
40
5
0.7
2.0
mA
mA
µA
pF
V
V
–100
+100
10
–100
+100
10
–100
+ 100
10
µA
µA
pF
NOTES
1
Tested at V
CC
= 4.5 V, 5.0 V and 5.5 V for A, B grades; 4.75 V, 5.0 V and 5.5 V for S grade.
Specifications shown in
boldface
are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels. All min and max specifications
are guaranteed, although only those shown in boldface are tested on all production units.
Specifications subject to change without notice.
REV. A
–3–
AD670
ABSOLUTE MAXIMUM RATINGS*
V
CC
to Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V to +7.5 V
Digital Inputs (Pins 11–15) . . . . . . . . . . . –0.5 V to V
CC
+0.5 V
Digital Outputs (Pins 1–9) . Momentary Short to V
CC
or Ground
Analog Inputs (Pins 16–19) . . . . . . . . . . . . . . . –30 V to +30 V
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