AD565A(RevF) 查看數據表（PDF） - Analog Devices
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AD565A Datasheet PDF : 12 Pages
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AD565A
CONNECTING THE AD566A FOR BUFFERED VOLTAGE
OUTPUT
The standard current-to-voltage conversion connections using an
operational amplifier are shown in Figures 4, 5, and 6 with the
preferred trimming techniques. If a low offset operational amplifier
(OP77, AD741L, OP07) is used, excellent performance can be
obtained in many situations without trimming (an op amp with
less than 0.5 mV max offset voltage should be used to keep offset
errors below 1/2 LSB). If a 50 Ω fixed resistor is substituted for the
100 Ω trimmer, unipolar zero typically is within ±1/2 LSB (plus op
amp offset), and full-scale accuracy is within 0.1% (0.25% max).
Substituting a 50 Ω resistor for the 100 Ω bipolar offset trimmer
gives a bipolar zero error typically within ± 2 LSB (0.05%).
The AD509 is recommended for buffered voltage-output
applications that require a settling time to ± 1/2 LSB of 1 μs. The
feedback capacitor is shown with the optimum value for each
application; this capacitor is required to compensate for the
25 pF DAC output capacitance.
FIGURE 4. UNIPOLAR CONFIGURATION
This configuration provides a unipolar 0 V to 10 V output range.
In this mode, the bipolar terminal, Pin 7, should be grounded if not
used for trimming.
AD566A
100⍀
100k⍀
BIPOLAR OFF
+15V
R1
50k⍀
–15V
20V SPAN
9.95k⍀ 5k⍀
10V SPAN
R2
100⍀
REF
IN 19.95k⍀
0.5mA
+V 10V EREF
AD561
20k⍀
IREF
REF
GND
POWER
GND
5k⍀
IO 8k⍀
DAC
IOUT =
4 ؋ IREF
؋ CODE
CODE
INPUT
–VEE
MSB
LSB
DAC
OUT
10pF
AD509
2.4k⍀
Figure 4. 0 V to 10 V Unipolar Voltage Output
STEP II . . . GAIN ADJUST
Turn all bits ON and adjust 100 Ω gain trimmer, R2, until the
output is 9.9976 V. (Full scale is adjusted to 1 LSB less than
nominal full scale of 10.000 V.) If a 10.2375 V full scale is desired
(exactly 2.5 mV/bit), insert a 120 Ω resistor in series with the
gain resistor at Pin 10 to the op amp output.
FIGURE 5. BIPOLAR CONFIGURATION
This configuration provides a bipolar output voltage from
–5.000 V to +4.9976 V, with positive full scale occurring with
all bits ON (all 1s).
R1
100⍀
BIPOLAR OFF
AD566A
9.95k⍀ 5k⍀
20V SPAN
10V SPAN
R2
100⍀
REF
IN 19.95k⍀
0.5mA
+V 10V EREF
AD561
20k⍀
IREF
REF
GND
POWER
GND
5k⍀
IO 8k⍀
DAC
IOUT =
4 ؋ IREF
؋ CODE
CODE
INPUT
–VEE
MSB
LSB
DAC
OUT
10pF
AD509
2.4k⍀
Figure 5. ±5 V Bipolar Voltage Output
STEP I . . . OFFSET ADJUST
Turn OFF all bits. Adjust 100 Ω trimmer R1 to give –5.000
output V.
STEP II . . . GAIN ADJUST
Turn ON all bits. Adjust 100 Ω gain trimmer R2 to give a read-
ing of +4.9976 V.
Please note that it is not necessary to trim the op amp to obtain
full accuracy at room temperature. In most bipolar situations,
an op amp trim is unnecessary unless the untrimmed offset drift
of the op amp is excessive.
STEP I . . . ZERO ADJUST
Turn all bits OFF and adjust zero trimmer, R1, until the output
reads 0.000 V (1 LSB = 2.44 mV). In most cases, this trim is
not needed, but Pin 7 should then be connected to Pin 12.
REV. F
–9–
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