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PDF AD571 Data sheet ( Hoja de datos )
| Número de pieza | AD571 | |
| Descripción | 10-Bit A/D Converter | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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a
10-Bit A/D Converter
AD571*
FEATURES
Complete A/D Converter with Reference and Clock
Fast Successive Approximation Conversion: 40 s max
No Missing Codes Over Temperature
0؇C to +70؇C: AD571K
–55؇C to +125؇C: AD571S
Digital Multiplexing: Three-State Outputs
18-Pin Ceramic DIP
Low Cost Monolithic Construction
PRODUCT DESCRIPTION
The AD571 is an 10-bit successive approximation A/D con-
verter consisting of a DAC, voltage reference, clock, compara-
tor, successive approximation register and output buffers—all
fabricated on a single chip. No external components are re-
quired to perform a full accuracy 10-bit conversion in 40 µs.
Operating on supplies of +5 V to +15 V and –15 V, the
AD571 will accepts analog inputs of 0 V to +10 V unipolar of
± 5 V bipolar, externally selectable. When the BLANK and
CONVERT input is driven low, the three-state outputs will be
open and a conversion will commence. Upon completion of the
conversion, the DATA READY line goes low and the data ap-
pears at the output. Pulling the BLANK and CONVERT input
high blanks the outputs and readies the device for the next con-
version. The AD571 executes a true 10-bit conversion with no
missing codes in 40 µs maximum.
The AD571 is available in two version for the 0°C to +70°C
temperature range, the AD571J and K. The AD571S guarantees
10-bit accuracy and no missing codes from –55°C to +125°C.
*Covered by Patent Nos. 3,940,760; 4,213,806; 4,136,349.
FUNCTIONAL BLOCK DIAGRAM
DIGITAL
BLANK &
V+ V– COMMON CONVERT CONTROL
10 12
16
11
ANALOG 13
IN
5k
B&C
ANALOG 14
COMMON
COMPARATOR
BIPOLAR
OFFSET 15
CONTROL
10-BIT
CURRENT
OUTPUT
DAC
10-BIT
SAR
INT.
CLOCK
DATA
READY
3 STATE
BUFFERS
TEMPERATURE COMPENSATED
BURIED ZENER REFERENCE
AND DAC CONTROL
AUTO BLANK
CONTROL
AD571
17
DATA READY
9 MSB
8
7
6
5 BIT
4 OUTPUTS
3
2
1
18 LSB
PRODUCT HIGHLIGHTS
1. The AD571 is a complete 10-bit A/D converter. No external
components are required to perform a conversion. Full-scale
calibration accuracy of ± 0.3% is achieved without external
trims.
2. The AD571 is a single chip device employing the most ad-
vanced IC processing techniques. Thus, the user has at his
disposal a truly precision component with the reliability and
low cost inherent in monolithic construction,
3. The AD571 accepts either unipolar (0 V to +10 V) or bipolar
(–5 V to +5 V) analog inputs by grounding or opening a
single pin.
4. The device offers true 10-bit accuracy and exhibits no miss-
ing codes over its entire operating temperature range.
5. Operation is guaranteed with –15 V and +5 V or +15 V sup-
plies. The device will also operate with a –12 V supply.
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  
AD571
ZERO OFFSET
The apparent zero point of the AD571 can be adjusted by
inserting an offset voltage between the analog common of the
device and the actual signal return or signal common. Figure 7
illustrates two methods of providing this offset. Figure 7a shows
how the converter zero may be offset by up to ± 3 bits to correct
the device initial offset and/or input signal offsets. As shown, the
circuit gives approximately symmetrical adjustment in unipolar
mode. In bipolar mode R2 should be omitted to obtain a sym-
metrical range.
INPUT
SIGNAL
R1
10Ω
SIGNAL COMMON
AIN
R2
7.5kΩ
AD571
R3
4.7kΩ
ACOM
R4
10kΩ
+15V
–15V
ZERO OFFSET ADJ
±3 BIT RANGE
Figure 7a.
INPUT
SIGNAL
R1
2.7Ω OR
5Ω POT
AIN
AD571
ACOM
NOTE: During a conversion transient currents from the analog
common terminal will disturb the offset voltage. Capacitive de-
coupling should not be used around the offset network. These
transients will settle as appropriate during a conversion. Capaci-
tive decoupling will “pump up” and fail to settle resulting in
conversion errors. Power supply decoupling which returns to
analog signal common should go to the signal input side of the
resistive offset network.
OUTPUT
CODE
0000000100
0000000011
0000000010
0000000001
0000000000
0V 10mV 30mV 50mV
INPUT VOLTAGE
NORMAL CHARACTERISTICS
REFERRED TO ANALOG COMMON
OUTPUT
CODE
0000000100
0000000011
0000000010
0000000001
0000000000
0V 10mV 30mV 50mV
INPUT VOLTAGE
OFFSET CHARACTERISTICS WITH
2.7Ω IN SERIES WITH ANALOG COMMON
SIGNAL COMMON
1/2 BIT ZERO OFFSET
Figure 8. AD571 Transfer Curve—Unipolar Operation
(Approximate Bit Weights Shown for Illustration, Nominal
Bit Weights ϳ 9.766 mV)
Figure 7b.
Figure 8 shows the nominal transfer curve near zero for an
AD571 in unipolar mode. The code transitions are at the edges
of the nominal bit weights. In some applications it will be pref-
erable to offset the code transitions so that they fall between the
nominal bit weights, as shown in the offset characteristics. This
offset can easily be accomplished as shown in Figure 7b. At bal-
ance (after a conversion) approximately 2 mA flows into the
analog common terminal. A 2.7 Ω resistor in series with this
terminal will result in approximately the desired 1/2 bit offset of
the transfer characteristics. The nominal 2 mA analog common
current is not closely controlled in production. If high accuracy
is required, a 5 Ω potentiometer (connected as a rheostat) can
be used as R1. Additional negative offset range may be obtained
by using larger values of R1. Of course, if the zero transition
point is changed, the full-scale transition point will also move.
Thus, if an offset of 1/2 LSB is introduced, full-scale trimming
as described on previous page should be done with an analog in-
put of 9.985 volts.
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 –5.0 volt signal will give a 10-bit code of 0000000000; an in-
put of 0.00 volts results in an output code of 1000000000;
+4.99 volts at the input yields 1111111111. The nominal trans-
fer curve is shown in Figure 9.
OUTPUT
CODE
10000 00010
10000 00001
10000 00000
01111 11111
01111 11110
0
–30 –20 –10 0 +10 +20 +30
INPUT VOLTAGE – mV
Figure 9. AD571 Transfer Curve—Bipolar Operation
REV. A
–5–
5 Page | ||
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| PDF Descargar | [ Datasheet AD571.PDF ] | |
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