AD571 데이터 시트보기 (PDF) - Analog Devices
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AD571 Datasheet PDF : 9 Pages
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AD571
BIT 9 1
18 BIT 10 (LSB)
BIT 8 2
17 DATA READY
BIT 7 3
16 DIGITAL COM
BIT 6 4 AD571 15 BIPOLAR OFF
BIT 5 5 TOP VIEW 14 ANALOG COM
(Not to Scale)
BIT 4 6
13 ANALOG IN
BIT 3 7
12 V–
BIT 2 8
(MSB) BIT 1 9
11 BLK AND CONV
10 V+
Figure 3. AD571 Pin Connections
FULL-SCALE CALIBRATION
The 5 kΩ thin-film input resistor is laser trimmed to produce a
current which matches the full-scale current of the internal
DAC—plus about 0.3%—when a full-scale analog input voltage
of 9.990 volts (10 volts—1 LSB) is applied at the input. The in-
put resistor is trimmed in this way so that if a fine trimming po-
tentiometer is inserted in series with the input signal, the input
current at the full-scale input voltage can be trimmed down to
match the DAC full-scale current as precisely as desired. How-
ever, for many applications the nominal 9.99 volt full scale can
be achieved to sufficient accuracy by simply inserting a 15 Ω re-
sistor in series with the analog input to Pin 13. Typical full-scale
calibration error will then be about ± 2 LSB or ± 0.2%. If a more
precise calibration is desired, a 50 Ω trimmer should be used in-
stead. Set the analog input at 9.990 volts, and set the trimmer
so that the output code is just at the transition between
1111111110 and 1111111111. Each LSB will then have a weight
of 9.766 mV. If a nominal full scale of 10.24 volts is desired
(which makes the LSB have a value of exactly 10.00 mV), a
100 Ω resistor in series with a 100 Ω trimmer (or a 200 Ω trim-
mer with good resolution) should be used. Of course, larger
full-scale ranges can be arranged by using a larger input resistor,
but linearity and full-scale temperature coefficient may be com-
promised if the external resistor becomes a sizable percentage
of 5 kΩ.
BIT 9 1
18
BIT 8 2
17
BIT 7 3
16
BIT 6 4 AD571 15
BIT 5 5 TOP VIEW 14
(Not to Scale)
BIT 4 6
13
BIT 3 7
12
BIT 2 8
11
(MSB) BIT 1 9
10
BIT 10 (LSB)
DATA READY
DIGITAL COM
(SHORT TO COM FOR
BIPOLAR CONTROL UNIPOLAR, OPEN FOR BIPOLAR)
ANALOG COM (TOLERATES 200mV TO
DIGITAL COM)
–15V
RIN
BLK AND CONV
ANALOG IN
15Ω FIXED OR
50Ω VARIABLE
(SEE TEXT)
+5V
Figure 4. Standard AD571 Connections
BIPOLAR OPERATION
The standard unipolar 0 V to +10 V range is obtained by short-
ing the bipolar offset control pin to digital common. If the pin is
left open, the bipolar offset current will be switched into the
comparator summing node, giving a –5 V to +5 V range with an
offset binary output code. (–5.00 volts in will give a 10-bit code
of 0000000000; an input of 0.00 volts results in an output code of
1000000000 and 4.99 volts at the input yields the 1111111111).
The bipolar offset control input is not directly TTL compatible,
but a TTL interface for logic control can be constructed as
shown in Figure 5.
+5V
USE ACTIVE
PULL-UP GATE
TTL
GATE
3x IN4148
5V COM
B&C
AIN AD571
ACOM
DR
BIPOLAR
OFFSET
CONTROL
DCOM
DATA 10 BITS
30kΩ
15V COM
–15V
Figure 5. Bipolar Offset Controlled by Logic Gate
Gate Output = 1: Unipolar 0 V–10 V Input Range
Gate Output = 0: Bipolar ±5 V Input Range
COMMON-MODE RANGE
The AD571 provides separate analog and digital common con-
nections. The circuit will operate properly with as much as
± 200 mV of common-mode range between the two commons.
This permits more flexible control of system common bussing
and digital and analog returns.
In normal operation the analog common terminal may generate
transient currents of up to 2 mA during a conversion. In addi-
tion, a static current of about 2 mA will flow into analog com-
mon in the unipolar mode after a conversion is complete. An
additional 1 mA will flow in during a blank interval with zero
analog input. The analog common current will be modulated by
the variations in input signal.
The absolute maximum voltage rating between the two com-
mons is ± 1 volt. We recommend that a parallel pair of back-to-
back protection diodes can be connected between the commons
if they are not connected locally.
11
10
9
8
7
6
5
4
3
2
1.5
1
–50 –25
0
25
50 70
TEMPERATURE – °C
C = CONVERT MODE
B = BLANK MODE
I –15V,C
I +15V,C
I –15V,B
I +15V,B
I +5V,C
I +5V,B
100 125
Figure 6. AD571 Power Supply Current vs. Temperature
–4–
REV. B
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