High-performance analogue measurement using internal enhanced PWM and ADC of a DSP-chip

Abstract

Modern control-oriented and general-purpose low- cost digital signal processor (DSP) chips include multiple 16-bit pulse-width modulators (PWM), in some cases with enhanced 8- bit part with possibility to adjust the PWM in fractions of the digital clock ("micro-steps"). Such PWM work at clock frequencies of 100 MHz and higher and can be used as a precise digital-to-analog converters (DAC). Such DSP chips also include multichannel (multiplexed) analog-to-digital converter ADC, of up to 12-bits resolution, working at conversion rate of up to 10 MHz. So, combining these resources together, with few extra components, high-performance analog-to-digital conversion is possible. In the current paper possibility of achieving of up to 20-bit resolution and measurement of frequencies of frequencies to tens of kHz or even more - is proposed, investigated and discussed. A PWM is used as the DAC in the compensation feedback path of the total analog-to-digital conversion path.