AD8600 查看數據表（PDF） - Analog Devices
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AD8600 Datasheet PDF : 16 Pages
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AD8600
Unipolar Output Operation
The AD8600 is configured to give unipolar operation. The full-
scale output voltage is equivalent to the reference input voltage
minus 1 LSB. The output is dependent upon the digital code
and follows Table III. The actual numbers given for the analog
output are calculated assuming a +2.5 V reference.
Table III. Unipolar Code Table
DAC
Binary Input
MSB LSB
Analog Output
Table IV. Bipolar Code Table
DAC
Binary Input
MSB LSB Analog Output
1111 1111
1000 0001
1000 0000
0111 1111
0000 0001
0000 0000
+2 VREF (255/256) – VREF = +2.49 V
+2 VREF (129/256) – VREF = +0.02 V
+2 VREF (128/256) – VREF = +0.00 V
+2 VREF (127/256) – VREF = –0.02 V
+2 VREF (001/256) – VREF = –2.48 V
+2 VREF (000/256) – VREF = –2.50 V
1111 1111
1000 0001
1000 0000
0111 1111
0000 0001
0000 0000
+VREF (255/256) = +2.49 V
+VREF (129/256) = +1.26 V
+VREF (128/256) = +1.25 V
+VREF (127/256) = +1.24 V
+VREF (001/256) = +0.01 V
+VREF (000/256) = +0.00 V
E Bipolar Output Operation
The AD8600 can be configured for bipolar operation with the
addition of an op amp for each output as shown in Figure 20.
T The output will now have a swing of ± VREF, as detailed in Table
IV. This modification is only needed on those channels that re-
quire bipolar outputs. For channels which only require unipolar
output, no external amplifier is needed. The OP495 quad am-
E plifier is chosen for the external amplifier because of its low
power, rail-to-rail output swing, and DC accuracy. Again, the
values calculated for the analog output are based upon an as-
L sumed +2.5 V reference.
VREF
R1
R1
10k
10k
O VREF
S AD8600
+5V
1/4
OUTø OP495
–5V
VOUT
OB Figure 20. Circuit for Bipolar Output Operation
Interfacing to the 68HC11 Microcontroller
The 68HC11 is a popular microcontroller from Motorola,
which is easily interfaced to the AD8600. The connections be-
tween the two components are shown in Figure 21. Port C of
the 68HC11 is used as a bidirectional input/output data port to
write to and read from the AD8600. Port B is used for address-
ing and control information. The bottom 4 LSBs of Port B are
the address, and the top 4 MSBs are the control lines (LD, CS,
EN, and R/W). The microcode for the 68 HC11 is shown in
Figure 22. The comments in the program explain the function
of each step. Three routines are included in this listing: read
from the AD8600, write to the AD8600, and a continuous loop
that generates a saw-tooth waveform. This loop is used in the
application below.
8
PC0–PC7
4
PB0–PB3
PB4
MOTOROLA
68HC11
PB5
PB6
GND
PB7
DB0–DB7
A0–A3
LD
AD8600
EN
R/ W
DGND1, DGND2
CS
DACGND
DIGITAL GROUND
ANALOG GROUND
Figure 21. Interfacing the 68HC11 to the AD8600
REV. 0
–11–
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