Calculating the total power consumption of the
device requires all of the supply inputs and DAC loads to be known. Equation 7 calculates the total power, Each component is the power contributed by a
supply or DAC loads.
Equation 7.
where
- PIO is the power consumed by the
device from the VIO supply:
Equation 8.
- PDD is the power consumed by the
device from the VDD supply:
Equation 9.
- PCC is the power consumed by the
device from the VCC supply:
Equation 10.
- PSS is the power consumed by the
device from the VSS supply:
Equation 11.
- PDAC-LOAD is the power consumed by the
device as a result of the DAC loads from the sourcing or sinking supply. The
power of each DAC channel can be calculated separately, then summed to find the
total power of the DAC loads. The power depends not only on the voltage of the
DAC output, but also on the difference between the current sourcing or sinking
supply and the DAC output voltage. The following equation shows how to calculate
PDAC-LOAD:
Equation 12.
Figure 8-6 shows the load configuration in both the positive output range and negative
output range.
When the device is in the
positive output range, the device is likely sourcing current. While in the negative
range, the device is likely sinking current. The difference between the supply
voltage and the DAC output voltage is VSUPPLY-LOAD, as shown in the
following equations.
When the device is in the positive output range,
VSUPPLY-LOAD can be calculated as:
Equation 13.
When the device is in the negative output range,
VSUPPLY-LOAD can be calculated as:
Equation 14.