Using PWM Output as a Digital-to-Analog Converter on DSP

This paper presents a method for utilizing the on-chip PWM (pulse width modulated) generators on a TMS320C240 DSP for digital-to-analog (D/A) conversion. The method involves analog low-pass filtering the PWM signal to remove high frequency components, leaving only the low-frequency content. Theoretical and experimental results are presented to quantify the achievable bit resolution. In addition, analog low-pass filter design is discussed and an example 3rd order filter design is given.