SBAS996B May   2020  – April 2021 AMC3306M25

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal Information
    5. 6.5  Power Ratings
    6. 6.6  Insulation Specifications
    7. 6.7  Safety-Related Certifications
    8. 6.8  Safety Limiting Values
    9. 6.9  Electrical Characteristics
    10. 6.10 Switching Characteristics
    11. 6.11 Timing Diagrams
    12. 6.12 Insulation Characteristics Curves
    13. 6.13 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Analog Input
      2. 7.3.2 Modulator
      3. 7.3.3 Isolation Channel Signal Transmission
      4. 7.3.4 Digital Output
        1. 7.3.4.1 Output Behavior in Case of a Full-Scale Input
        2. 7.3.4.2 Output Behavior in Case of a High-Side Supply Failure
      5. 7.3.5 Isolated DC/DC Converter
      6. 7.3.6 Diagnostic Output
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Digital Filter Usage
    2. 8.2 Typical Application
      1. 8.2.1 Solar Inverter Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Shunt Resistor Sizing
          2. 8.2.1.2.2 Input Filter Design
          3. 8.2.1.2.3 Bitstream Filtering
        3. 8.2.1.3 Application Curve
      2. 8.2.2 What To Do and What Not To Do
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Device Nomenclature
        1. 11.1.1.1 Isolation Glossary
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.3.2 Modulator

The second-order, switched-capacitor, feed-forward ΔΣ modulator conceptualized in Figure 7-2 is implemented in the AMC3306M25. The analog input voltage VIN and the output V5 of the 1-bit digital-to-analog converter (DAC) are differentiated, providing an analog voltage V1 at the input of the first integrator stage. The output of the first integrator feeds the input of the second integrator stage, resulting in an output voltage V3 that is differentiated with the input signal VIN and the output of the first integrator V2. Depending on the polarity of the resulting voltage V4, the output of the comparator is changed. In this case, the 1-bit DAC responds on the next clock pulse by changing the associated analog output voltage V5, causing the integrators to progress in the opposite direction, and forcing the value of the integrator output to track the average value of the input.

GUID-20201221-CA0I-8TVQ-SSXL-JKCN5LF2PXGG-low.gif Figure 7-2 Block Diagram of a Second-Order Modulator

The modulator shifts the quantization noise to high frequencies, as depicted in Figure 7-1. Therefore, use a low-pass digital filter at the output of the device to increase the overall performance. This filter is also used to convert the 1-bit data stream at a high sampling rate into a higher-bit data word at a lower rate (decimation). TI's C2000™ and Sitara™ microcontroller families offer a suitable programmable, hardwired filter structure termed a sigma-delta filter module (SDFM) optimized for usage with the AMC3306M25. Alternatively, a field-programmable gate array (FPGA) or complex programmable logic device (CPLD) can be used to implement the filter.