Hello ,
I am using PWM for DAC operation in TMS320F28069 running with SYS_CLK of 90MHz.
The PWM is operating at 48KHz, the corresponding Time Period value would be 1875 (90M / 48K).
I have a Sallen Key Low pass filter (after ePWM stage) with a cutoff freq of 300 Hz.
To test the working of DAC, I use a sine table constants.
The sine table constants have values ranging from -1 to +1, I scale them to the range 0 to 1.0
This scaled values in tha range 0 to 1.0 would correspond to duty %.
Issue:
The sine wave is clipped. The clean sine wave is obseved in the range 0.3 to 0.7 % duty cycle.
Anything below 0.3 duty & above 0.7 duty is clipped.
So I am effectively able to use count ranging from 562.5 to 1312.5 (0.3*1875 to 0.7*1875)
1. Any hints/suggestion to use the complete range 0 - 1875 counts?
2. How to test the improved DAC resoultion upon usage of HRPWM over standard PWM?
regards,
Hemanth