AD565-566A AD [Analog Devices], AD565-566A Datasheet - Page 9

• Manufacturer Part Number: AD565-566A
• Description: High Speed 12-Bit Monolithic D/A Converters
• Manufacturer: AD [Analog Devices]

CONNECTING THE AD566A FOR BUFFERED VOLTAGE
OUTPUT
The standard current-to-voltage conversion connections using
an operational amplifier are shown here with the preferred trim-
ming techniques. If a low offset operational amplifier (AD510L,
AD517L, AD741L, AD301AL, AD OP07) is used, excellent
performance can be obtained in many situations without trim-
ming (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
will typically be within ± 1/2 LSB (plus op amp offset), and full
scale accuracy will be within 0.1% (0.25% max). Substituting a
50 Ω resistor for the 100 Ω bipolar offset trimmer will give a
bipolar zero error typically within ± 2 LSB (0.05%).
The AD509 is recommended for buffered voltage-output appli-
cations which require a settling time to ± 1/2 LSB of one micro-
second. The feedback capacitor is shown with the optimum
value for each application; this capacitor is required to compen-
sate for the 25 picofarad DAC output capacitance.
FIGURE 4. UNIPOLAR CONFIGURATION
This configuration will provide a unipolar 0 volt to +10 volt
output range. In this mode, the bipolar terminal, Pin 7, should
be grounded if not used for trimming.
STEP I . . . ZERO ADJUST
Turn all bits OFF and adjust zero trimmer, R1, until the output
reads 0.000 volts (1 LSB = 2.44 mV). In most cases this trim is
not needed, but Pin 7 should then be connected to Pin 12.
STEP II . . . GAIN ADJUST
Turn all bits ON and adjust 100 Ω gain trimmer, R2, until the
output is 9.9976 volts. (Full scale is adjusted to 1 LSB less than
nominal full scale of 10.000 volts.) 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.
REV. D
+V
100
10V
Figure 4. 0 V to +10 V Unipolar Voltage Output
R2
E
AD561
REF
GND
REF
REF
IN
–V
20k
AD566A
19.95k
EE
POWER
GND
0.5mA
I
REF
9.95k
100
MSB
INPUT
CODE
I
4
OUT
DAC
BIPOLAR OFF
5k
5k
CODE
I
REF
=
I
LSB
O
8k
100k
DAC
OUT
20V SPAN
10V SPAN
+15V
–15V
R1
50k
2.4k
AD509
10pF
–9–
FIGURE 5. BIPOLAR CONFIGURATION
This configuration will provide a bipolar output voltage from
–5.000 volts to +4.9976 volts, with positive full scale occurring
with all bits ON (all 1s).
STEP I . . . OFFSET ADJUST
Turn OFF all bits. Adjust 100 Ω trimmer R1 to give –5.000
output volts.
STEP II . . . GAIN ADJUST
Turn ON all bits. Adjust 100 Ω gain trimmer R2 to give a read-
ing of +4.9976 volts.
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.
+V
10V
100
E
AD561
R2
REF
GND
REF
Figure 5. ± 5 V Bipolar Voltage Output
REF
IN
–V
20k
AD566A
19.95k
EE
POWER
GND
100
R1
0.5mA
I
REF
9.95k
MSB
AD565A/AD566A
CODE
INPUT
I
4
OUT
DAC
BIPOLAR OFF
5k
CODE
5k
I
REF
=
I
LSB
O
8k
DAC
OUT
20V SPAN
10V SPAN
2.4k
AD509
10pF