SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
Many of the configuration parameters for the DPWM, including the mode, are in DPWM Control Register 1. For automatic mode switching, some of these parameters are duplicated in the Auto Config Mid and Auto Config High registers.
If automatic mode switching is enabled, the Filter Duty signal is used to select which of these three registers is used. There are 4 registers which are used to select the points at which the mode switching takes place. They are used as shown below:
As shown, the registers are used in pairs for hysteresis. The transition from Control Register 1 to Auto Config Mid only takes place when the Filter Duty goes above the Low Upper threshold. It does not go back to Control Register 1 until the Low Lower Threshold is passed. This prevents oscillation between modes if the filter duty is close to a mode switching point. In some applications it is necessary to make the values the same, disabling hysteresis. This has to be done to make the DPWM signals from the two modes match properly at the mode switching point.