dac0830-mwc National Semiconductor Corporation, dac0830-mwc Datasheet - Page 15

• Manufacturer Part Number: dac0830-mwc
• Description: 8-bit ?p Compatible, Double-buffered D To A Converters
• Manufacturer: National Semiconductor Corporation

DAC0830 Series Application Hints
2.6 Full-Scale Adjustment
In the case where the matching of R
R-2R ladder (typically
accuracy in a particular application, the V
adjusted or an external resistor and potentiometer can be
added as shown in Figure 10 to provide a full-scale adjust-
ment.
The temperature coefficients of the resistors used for this
adjustment are of an important concern. To prevent degra-
dation of the gain error temperature coefficient by the exter-
nal resistors, their temperature coefficients ideally would
have to match that of the internal DAC resistors, which is a
highly impractical constraint. For the values shown in Figure
10 , if the resistor and the potentiometer each had a tempera-
ture coefficient of
±
100 ppm/˚C maximum, the overall gain
±
0.2%) is insufficient for full-scale
*THESE RESISTORS ARE AVAILABLE FROM BECKMAN INSTRUMENTS, INC. AS THEIR PART NO. 694-3-R10K-D
1 1
1 1
1 0
0 1
0 0
0 0
MSB
1
0
0
1
1
0
Input Code
fb
1
0
0
1
1
0
to the R value of the
REF
1
0
0
1
1
0
voltage can be
1
0
0
1
1
0
1
0
0
1
1
0
LSB
1
0
0
1
1
0
FIGURE 9.
(Continued)
15
+V
REF
error temperature coefficent would be degraded a maximum
of 0.0025%/˚C for an adjustment pot setting of less than 3%
of R
2.7 Using the DAC0830 in a Voltage Switching
Configuration
The R-2R ladder can also be operated as a voltage switch-
ing network. In this mode the ladder is used in an inverted
manner from the standard current switching configuration.
The reference voltage is connected to one of the current
output terminals (I
for complementary binary) and the output voltage is taken
from the normal V
voltage in the range from 0V to 255/256 V
of the applied digital code as shown in Figure 11 .
fb
IDEAL V
.
OUT
OUT1
−V
REF
REF
for true binary digital control, I
pin. The converter output is now a
00560840
REF
as a function
www.national.com
OUT2
is