AD668 데이터 시트보기 (PDF) - Analog Devices
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AD668 Datasheet PDF : 16 Pages
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AD668
Nominal
Analog
Input
1V
0 V to 1 V
Unipolar
Unbuffered VOUT
AIN = Pins 21 + 22
1.25 V
Unipolar
Unbuffered VOUT
AIN = Pin 22
Pin 21 Grounded
Unipolar
Unbuffered VOUT
5V
AIN = Pin 21
Pin 22 Grounded
(See Figure 7)
Table II. AD668 Topology Variations
OUTPUT LEVELS
–500 mV to +500 mV
Bipolar
Unbuffered VOUT
AIN = Pins 21 + 22
Bipolar
Unbuffered VOUT
AIN = Pin 22
Pin 21 Grounded
(See Figure 8)
Bipolar
Unbuffered VOUT
AIN = Pin 21
Pin 22 Grounded
0 V to –10 V
Unipolar
Buffered VOUT
AIN = Pins 21 + 22
External Amplifier
(See Figure 10)
Unipolar
Buffered VOUT
AIN = Pin 22
Pin 21 Grounded
External Amplifier
Unipolar
Buffered VOUT
AIN = Pin 21
Pin 22 Grounded
External Amplifier
+5 V to –5 V
Bipolar
Buffered VOUT
AIN = Pins 21 + 22
External Amplifier
Bipolar
Buffered VOUT
AIN = Pin 22
Pin 21 Grounded
External Amplifier
Bipolar
Buffered VOUT
AIN = Pin 21
Pin 22 Grounded
External Amplifier
–1 V to +1 V
Bipolar
Unbuffered VOUT
AIN = Pins 21 + 22
RL (Pin 19) Tied
To IOUT (Pin 20)
Bipolar
Unbuffered VOUT
AIN = Pin 22
Pin 21 Grounded
RL (Pin 19) Tied
To IOUT (Pin 20)
Bipolar
Unbuffered VOUT
AIN = Pin 21
Pin 22 Grounded
RL (Pin 19) Tied
To IOUT (Pin 20)
(See Figure 9)
5k series resistor in the dc path. Note that because of the rela-
tively wide tolerance (± 20%) in the absolute value of the
AD668’s internal input divider resistors, substantial gain range
adjustment should be provided in the external series resistance.
Figure 11. AD586 Driving the AD668
mode (Pin 22 grounded, input into Pin 21). Fine adjustment of
the gain is provided by both the AD586 external trim resistor
and the 100 Ω potentiometer in series with the reference input.
The resistive divider at the reference input will draw approxi-
mately 1 mA from the AD586, leaving plenty of driving current
for other loads in the system.
AC HOOKUP: 1.25 V AC FULL SCALE, 2.5 V DC FULL
SCALE
The circuit shown in Figure 12 allows separate setting of dc ref-
erence bias point on a 2.5 V scale and capacitively coupled ac
signal on a 1.25 V scale. The basic reference input is configured
in the 1.25 V mode (Pin 21 grounded, Pin 22 used as the refer-
ence input.) The 2.5 V dc range is achieved by using an external
Figure 12. AC Hookup
DAC DRIVE: THE AD568 DRIVING THE AD668
The circuit shown in Figure 13 produces an analog output pro-
portional to the product of two digital inputs. The AD568 has
an on-board fixed reference and generates a full-scale output
voltage of 1.024 V (just as the AD668 does in its unbuffered
voltage output mode). This output voltage can be used to di-
rectly drive the AD668 in the 1 V reference input mode. Note
that in this case, the lower 410 codes of the AD568 are out-of-
bounds; they produce an undervoltage condition at the AD668
–10–
REV. A
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