AN 994: Drive-on-Chip Design Example for Intel Agilex® 7 Devices

ID 780361
Date 6/26/2023
Public
Document Table of Contents

5.1. Signal Sensing in Sigma-Delta

Sigma-delta modulators on the power board model convert analog signals to a one-wire digital bitstream. The design demodulates or filters the bitstream in the FPGA. The FPGA uses two types of sigma-delta filter IP in the FPGA, ADC modules and DC link modules, each with different scaling and offset.

The design downloads and filters all sigma delta inputs in parallel so no skew exists between the samples that it feeds to the software application.

Each ADC type has a different input and output ranges with the corresponding 'C' data type.

Table 3.  ADC Output Data
ADC Type Count Range C Data type
Sigma-delta ADC -32768…+32767 Signed 16-bit
Sigma-delta DC link 0…+32767 Signed 16-bit

Position feedback samples are scaled to a 23 bit unsigned integer, for consistency across all encoder types supported by this and previous Drive-on-Chip designs.

Table 4.  ADC ScalingThis table shows the ADC scaling for all signals, ADC type and board revision. The scaling depends on the way the power board processes the signals (e.g., value of current shunts, scaling, and offset in sense amplifiers).
Feedback Quantity Sigma Delta Interface IP Sigma Delta Scaling for Tandem Motion Power Board
Motor phase voltages ADC interface 545 counts/V
Motor input voltage DC Link interface 545 counts/V
Motor phase currents ADC interface 1024 counts/A