SPRUJ53B April 2024 – September 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
Each reference 12-bit DAC can be configured to drive a reference voltage into the negative input of the respective comparator. Some CMPSS instances also allow the low DAC output to be routed to a pin to act as an external DAC. In this case, all other CMPSS module functionality is not useable, including the high DAC, both comparators, ramp generation, and the digital filters.
Two sets of DACxVAL registers, DACxVALA and DACxVALS, are present for each reference 12-bit DAC. DACxVALA is a read-only register that actively controls the reference 12-bit DAC value. DACxVALS is a writable shadow register that loads into DACxVALA either immediately or synchronized with the next EPWMSYNCPER event. The high and low reference 12-bit DAC (DACx) can optionally source the register DACxVALA value from the ramp generator instead of the register DACxVALS.
The operating range of the reference 12-bit DAC is bounded by DACREF and VSSA. The reference 12-bit DAC is illustrated in Figure 17-3.
The output of the reference 12-bit DAC can be calculated as:
Users must design the system carefully so that if the input signal crosses either DACH or DACL and trips the associated comparator, the input signal stays more than a “CMPSS DAC output disturbance” away from the other comparator trip point for “CMPSS DAC disturbance time”.