SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
In addition to oversampling, Sample Trigger 1 offers several modes of calculation. The SAMPLE_TRIG1_MODE bit field selects from 4 of these:
On the diagrams earlier in this chapter, option 1 is called Adaptive Sample Trigger B, and option 3 is called Adaptive Sample Trigger A.
The Adaptive Offset comes from the DPWMADAPTIVE register, which is an 11 bit signed register. Without the Adaptive Offset, the sample trigger will be in the middle of the on-time for DPWMA in Normal and Multi Modes. The Adaptive Offset is used to correct for system delays in gate drivers, FET turn-on times and voltage and current sensing circuits. Using the Adaptive Offset properly can put the sample trigger in the middle of the voltage or current on-time. The adaptive offset register has the same resolution as the Sample Trigger Register – 16 nanoseconds. The adaptive register, though is not mapped the same. Bit 0 is the first usable bit. See Section 2.32 for more information.
Note that using adaptive offset will cause the phase delay of the control loop to change somewhat as the duty cycle changes.
The Fixed Offset in mode 3 is a value of 4. This is added to the DPWMADAPTIVE Register and to the Event 1 and Duty Terms.