BL4S200 User’s Manual
44
To stay within the maximum power dissipation of the D/A converter circuit, the maximum
D/A converter output current is 10 mA per channel for the voltage outputs. If you are
using the current outputs, keep the resistance driven by a current output channel above
1 k
to stay within the voltage compliance capability of the op-amp output circuit.
As Figure 17 shows, both the voltage and the current outputs for a particular channel are
driven by the same output on the D/A converter chip. As a result, either the
anaOut-
Volts()
or the
anaOutmAmps()
function calls will set both the voltage and the current
outputs corresponding to a particular channel. Pay attention to which function call you use
to set the D/A converter output — setting a current level using voltage function calls will
not produce a correctly calibrated output.
The D/A converter outputs are factory-calibrated and the calibration constants are stored in
the user block.
3.5.1 D/A Converter Calibration
To get the best results form the D/A converter, it is necessary to calibrate each mode (uni-
polar, bipolar, and current) that you intend to use. It is imperative that you calibrate each
of the D/A converter outputs in the same manner as they are to be used in the application.
The calibration table in software only holds calibration constants based on unipolar, bipo-
lar, and voltage or current operation.
Other factors affecting the calibration must be taken into
account by calibrating using the same mode and voltage/current setup as in the intended use.
Sample programs are provided to illustrate how to calibrate the various D/A outputs for
the three operating modes.
These sample programs are found in the
DAC
subdirectory in
SAMPLES\BLxS2xx
. See
Section 4.2.4 for more information on these sample programs and how to use them.
Mode
Calibrate
Voltage
DAC_CAL_VOLTS.C
Current
DAC_CAL_MA.C
