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PDF AD673 Data sheet ( Hoja de datos )
| Número de pieza | AD673 | |
| Descripción | 8-Bit A/D Converter | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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a
8-Bit A/D Converter
FEATURES
Complete 8-Bit A/D Converter with Reference, Clock
and Comparator
30 s Maximum Conversion Time
Full 8- or 16-Bit Microprocessor Bus Interface
Unipolar and Bipolar Inputs
No Missing Codes Over Temperature
Operates on +5 V and –12 V to –15 V Supplies
MIL-STD-883 Compliant Version Available
AD673*
FUNCTIONAL BLOCK DIAGRAM
VCC VSS
DIGITAL
COMMON CONVERT
ANALOG
IN
ANALOG
COMMON
5k
COMP-
ARATOR
BIPOLAR
OFFSET
CONTROL
8-BIT
CURRENT
OUTPUT
DAC
8-BIT
SAR
INT
CLOCK
MSB
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
LSB
DATA
ENABLE
GENERAL DESCRIPTION
The AD673 is a complete 8-bit successive approximation
analog-to-digital converter consisting of a DAC, voltage refer-
ence, clock, comparator, successive approximation register
(SAR) and 3-state output buffers—all fabricated on a single
chip. No external components are required to perform a full ac-
curacy 8-bit conversion in 20 µs.
The AD673 incorporates advanced integrated circuit design and
processing technologies. The successive approximation function
is implemented with I2L (integrated injection logic). Laser trim-
ming of the high stability SiCr thin-film resistor ladder network
insures high accuracy, which is maintained with a temperature
compensated sub-surface Zener reference.
Operating on supplies of +5 V and –12 V to –15 V, the AD673
will accept analog inputs of 0 V to +10 V or –5 V to +5 V. The
trailing edge of a positive pulse on the CONVERT line initiates
the 20 µs conversion cycle. DATA READY indicates comple-
tion of the conversion.
The AD673 is available in two versions. The AD673J as speci-
fied over the 0°C to +70°C temperature range and the AD673S
guarantees ± 1/2 LSB relative accuracy and no missing codes
from –55°C to +125°C.
Two package configurations are offered. All versions are also of-
fered in a 20-pin hermetically sealed ceramic DIP. The AD673J
is also available in a 20-pin plastic DIP.
*Protected by U.S. Patent Nos. 3,940,760; 4,213,806; 4,136,349; 4,400,689;
and 4,400,690.
DATA
READY
BURIED ZENER REF
AD673
PRODUCT HIGHLIGHTS
1. The AD673 is a complete 8-bit A/D converter. No external
components are required to perform a conversion.
2. The AD673 interfaces to many popular microprocessors
without external buffers or peripheral interface adapters.
3. The device offers true 8-bit accuracy and exhibits no missing
codes over its entire operating temperature range.
4. The AD673 adapts to either unipolar (0 V to +10 V) or
bipolar (–5 V to +5 V) analog inputs by simply grounding or
opening a single pin.
5. Performance is guaranteed with +5 V and –12 V or –15 V
supplies.
6. The AD673 is available in a version compliant with MIL-
STD-883. Refer to the Analog Devices Military Products
Databook or current AD673/883B data sheet for detailed
specifications.
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
1 page  
AD673
BIPOLAR CONNECTION
To obtain the bipolar –5 V to +5 V range with an offset binary
output code, the bipolar offset control pin is left open.
A –5.00 volt signal will give a 8-bit code of 00000000; an input
of 0.00 volts results in an output code of 10000000 and +4.961
volts at the input yields the 11111111 code. The nominal trans-
fer curve is shown in Figure 6.
Figure 6. AD673 Transfer Curve—Bipolar Operation
Note that in the bipolar mode, the code transitions are offset
1/4 LSB such that an input voltage of 0 volts –5 mV to +35 mV
yields the code representing zero (10000000). Each output code
is then centered on its nominal input voltage.
Full-Scale Calibration
Full-Scale Calibration is accomplished in the same manner as in
Unipolar operation except the full-scale input voltage is +4.61
volts.
Negative Full-Scale Calibration
The circuit in Figure 4a can also be used in Bipolar operation to
offset the input voltage (nominally –5 V) which results in the
000000 00 code. R2 should be omitted to obtain a symmetrical
range.
The bipolar offset control input is not directly TTL compatible
but a TTL interface for logic control can be constructed as
shown in Figure 7.
SAMPLE-HOLD AMPLIFIER CONNECTION
TO THE AD673
Many situations in high-speed acquisition systems or digitizing
rapidly changing signals require a sample-hold amplifier (SHA)
in front of the A-D converter. The SHA can acquire and hold a
signal faster than the converter can perform a conversion. A
SHA can also be used to accurately define the exact point in
time at which the signal is sampled. For the AD673, a SHA can
also serve as a high input impedance buffer.
Figure 8 shows the AD673 connected to the AD582 monolithic
SHA for high speed signal acquisition. In this configuration, the
AD582 will acquire a 10 volt signal in less than 10 µs with a
droop rate less than 100 µV/ms.
DR goes high after the conversion is initiated to indicate that re-
set of the SAR is complete. In Figure 8 it is also used to put the
AD582 into the hold mode while the AD673 begins its conver-
sion cycle. (The AD582 settles to final value well in advance of
the first comparator decision inside the AD673).
DR goes low when the conversion is complete placing the
AD582 back in the sample mode. Configured as shown in Fig-
ure 8, the next conversion can be initiated after a 10 µs delay to
allow for signal acquisition by the AD582.
Observe carefully the ground, supply, and bypass capacitor con-
nections between the two devices. This will minimize ground
noise and interference during the conversion cycle.
Figure 8. Sample-Hold Interface to the AD673
Figure 7. Bipolar Offset Controlled by Logic Gate
Gate Output = 1 Unipolar 0 V–10 V Input Range
Gate Output = 0 Bipolar ±5 V Input Range
REV. A
–5–
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet AD673.PDF ] | |
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