SBAS951B August   2019  – April 2020 AMC1336

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. Table 1.  Absolute Maximum Ratings
    2. Table 2.  ESD Ratings
    3. Table 3.  Recommended Operating Conditions
    4. Table 4.  Thermal Information
    5. Table 5.  Power Ratings
    6. Table 6.  Insulation Specifications
    7. Table 7.  Safety-Related Certifications
    8. Table 8.  Safety Limiting Values
    9. Table 9.  Electrical Characteristics
    10. Table 10. Switching Characteristics
    11. 6.1       Insulation Characteristics Curves
    12. 6.2       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 Clock Input
      5. 7.3.5 Digital Output
    4. 7.4 Device Functional Modes
      1. 7.4.1 Output Behavior in Case of a Full-Scale Input
      2. 7.4.2 AVDD Diagnostics and Fail-Safe Output
  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 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curve
      4. 8.2.4 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 Community 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 modulator implemented in the AMC1336, as conceptualized in Figure 42, is a second-order, switched-capacitor, feed-forward ΔΣ modulator. The analog input voltage VIN and the output V5 of the 1-bit digital-to-analog converter (DAC) are subtracted, 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.

AMC1336 ai_modulator_bas654.gifFigure 42. Block Diagram of a Second-Order Modulator

As depicted in Figure 39, the modulator shifts the quantization noise to high frequencies. 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 from the 1-bit data stream at a high sampling rate into a higher-bit data word at a lower rate (decimation). TI's microcontroller families TMS320F2807x and TMS320F2837x offer a suitable programmable, hardwired filter structure termed a sigma-delta filter module (SDFM) optimized for usage with the AMC1336. Furthermore, the SD24_B converters on the MSP430F677x microcontrollers offer a path to directly access the integrated sinc filters for a simple system-level solution for multichannel, isolated current sensing. An additional option is to use a suitable application-specific device, such as the AMC1210 (a four-channel digital sinc-filter). Alternatively, a field-programmable gate array (FPGA) can be used to implement the filter.