SBAS655F September   2014  – January 2020 AMC1304L05 , AMC1304L25 , AMC1304M05 , AMC1304M25

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Power Ratings
    6. 7.6  Insulation Specifications
    7. 7.7  Safety-Related Certifications
    8. 7.8  Safety Limiting Values
    9. 7.9  Electrical Characteristics: AMC1304x05
    10. 7.10 Electrical Characteristics: AMC1304x25
    11. 7.11 Switching Characteristics
    12. 7.12 Insulation Characteristics Curves
    13. 7.13 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Analog Input
      2. 8.3.2 Modulator
      3. 8.3.3 Digital Output
    4. 8.4 Device Functional Modes
      1. 8.4.1 Fail-Safe Output
      2. 8.4.2 Output Behavior in Case of a Full-Scale Input
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Digital Filter Usage
    2. 9.2 Typical Applications
      1. 9.2.1 Frequency Inverter Application
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curve
      2. 9.2.2 Isolated Voltage Sensing
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curve
      3. 9.2.3 What To Do and What Not To Do
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Examples
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Device Nomenclature
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Related Links
    4. 12.4 Receiving Notification of Documentation Updates
    5. 12.5 Community Resources
    6. 12.6 Trademarks
    7. 12.7 Electrostatic Discharge Caution
    8. 12.8 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

9.1.1 Digital Filter Usage

The modulator generates a bit stream that is processed by a digital filter to obtain a digital word similar to a conversion result of a conventional analog-to-digital converter (ADC). A very simple filter, built with minimal effort and hardware, is a sinc3-type filter, as shown in Equation 2:

Equation 2. AMC1304L05 AMC1304L25 AMC1304M05 AMC1304M25 ai_equation2_bas654.gif

This filter provides the best output performance at the lowest hardware size (count of digital gates) for a second-order modulator. All the characterization in this document is also done with a sinc3 filter with an oversampling ratio (OSR) of 256 and an output word duration of 16 bits.

The effective number of bits (ENOB) is often used to compare the performance of ADCs and ΔΣ modulators. Figure 53 shows the ENOB of the AMC1304 with different oversampling ratios. In this document, this number is calculated from the SNR by using Equation 3:

Equation 3. AMC1304L05 AMC1304L25 AMC1304M05 AMC1304M25 ai_equation3_bas654.gif
AMC1304L05 AMC1304L25 AMC1304M05 AMC1304M25 D053_SBAS654.gif
Figure 53. Measured Effective Number of Bits versus Oversampling Ratio

An example code for implementing a sinc3 filter in an FPGA is discussed in the Combining ADS1202 with FPGA Digital Filter for Current Measurement in Motor Control Applications application note (SBAA094), available for download at www.ti.com.