Flexible Interface for Synchronous Coherent DAQ Using Multiple ADCs (PRU-ICSS) Reference Design

This reference design demonstrates an interface implementation to multiple high-voltage bipolar input, 8-channel, multiplexed input SAR ADCs (6) via a Sitara Arm processor using a Programmable Real-Time Unit (PRU- ICSS) expands the number of input channels. The ADCs can be configured so that the same channels can be sampled simultaneously across all ADCs. This design highlights the PRU-ICSS's ability to handle a data rate of 1536ksps (each sample = 16 bits) (640 samples sampled per line cycle). For a 50Hz period, this equates to 32ksps per channel between 6 ADCs simultaneously (640 samples/period*50Hz*6 ADC*8 channels = 1536ksps). In addition, a second PRU is used to post-process the data to achieve coherent sampling.

characteristic

• ● Flexible interface to communicate with multiple SAR ADCs using PRU-ICSS (Sitara Processor)
• ● AC voltage and current measurement accuracy:
  • ● AC voltage: Accuracy is less than ±0.2% in the range of 2.5V to 120V
  • ● AC current: Accuracy less than ±0.2% in the range of 2.5A to 70A
  • ● Simultaneous sampling between six ADCs (16-bit, 500ksps/ADC)
• ● PRU-ICSS interface:
  • ● Programmable Real-Time Unit Industrial Communication Subsystem (PRU-ICSS) provides flexible data capture function to achieve channel expansion
  • ● Firmware-based approach allows reuse across different Sitara processors
  • ● Achieve coherent sampling by calculating the line period in software and adjusting the CS signal