This application note demonstrates the usage of the pipeline flash Analog to Digital Converter (ADC) system1 on the ADSP-21990. Section one will discuss the ADC library routines. In section two, an example will be used to demonstrate the usage of these routines. The last section shows some experimental results.
The document describes an application note for the ADSP-21990 processor focusing on the utilization of its Analog to Digital Converter (ADC). It details two specific library routines: ADC_Init for initializing the block and configuring interrupts, and ADC_Read for reading channel values with offset adjustments. The text explains the usage of DSP registers within these macros and references the hardware reference manual for further configuration details.
A software example is provided demonstrating how to utilize the ADC block to generate three-phase sine-wave PWM patterns where the amplitude is controlled by an ADC channel value. The note includes experimental results showing filtered sine PWM outputs with varying amplitude factors, illustrating the system's performance under different input voltage conditions.
| ADC Interrupt Assignment | USR2 |
|---|---|
| PWM Switching Frequency | 20kHz |
| Crystal Clock Frequency | 25MHz |
| Peripheral Clock Frequency | 12.5MHz |
| PWM Dead Time | 2us |
| PWM Sync Pulse Width | 440ns |
| Fundamental Frequency | 60Hz |
The library defines two routines: ADC_Init for initialization and configuring interrupts, and ADC_Read for reading channel values with offset adjustments.
The amplitude is controlled by the ADC channel value, which acts as an amplitude factor.
The implementation is performed in the ADC_EOC interrupt service routine.