VCM-DAS-3 Reference Manual
27
Analog Output
Analog Output Ranges and Resolution
VCM-DAS-3 provides six different analog output ranges (shown in Table 18), including four
bipolar ranges and two unipolar ranges. One of the bipolar ranges (
-
2.5 to +7.5V) is
asymmetrical. Power-up ranges are determined by jumper settings (see Power-up Span Range
Configuration). Ranges for individual channels can be set by software using the Set Span
command, available in enhanced mode.
The resolution for any output range is equal to the maximum possible range of output voltages
divided by the maximum number of possible steps. For a 12-bit D/A converter, the maximum
number of steps is 4096. The actual output codes range from 0 to 4095, which is the full range of
possible 12-bit binary numbers. (See Analog Output Data Representation.)
The table below shows the analog output ranges and resolutions available on the VCM-DAS-3.
Negative full scale refers to the output voltage for a code of 0, and positive full scale refers to the
output voltage for a code of 4095.
Table 18: Analog Output Ranges and Resolution
Full-Scale
Voltage
Bipolar or
Unipolar
Range
Name
Negative
Full Scale
Positive
Full Scale
Resolution
(1 LSB)
10V
Bipolar
±10V
-
10V
+9.9951V
4.88mV
5V
Bipolar
±5V
-
5V
+4.9963V
2.44mV
2.5V
Bipolar
±2.5V
-
2.5V
+2.4988V
1.22mV
7.5V
Bipolar
-
2.5 to +7.5V
-
2.5V
+7.4963V
2.44mV
10V
Unipolar
0-10V
0V
+9.9976V
2.44mV
5V
Unipolar
0-5V
0V
+4.9988V
1.22mV
S
ETTING A
S
PAN
R
ANGE
Power-up span ranges are determined for blocks of channels by jumper settings (see Power-up
Span Range Configuration); however, in enhanced mode, you can set the span range for any
individual channel. To perform a Set Span operation:
1.
Write the appropriate Set Span code (see Enhanced Control Register) to the CTRL field
of the ENCTRL register at I/O port 0x30A, combined with the channel number in the
SEL bits of the same register.
2.
Perform an LDAC operation by writing Ah to the CTRL field of the ENCTRL register,
combined with the channel number in the SEL field of the same register.
5
5