SBAS897C March   2018  – June 2022 AMC1311-Q1

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 Diagram
    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 Isolation Channel Signal Transmission
      3. 7.3.3 Analog Output
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Input Filter Design
        2. 8.2.2.2 Differential to Single-Ended Output Conversion
      3. 8.2.3 Application Curve
    3. 8.3 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 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

8.2.2 Detailed Design Procedure

The 100-μA, cross-current requirement at the maximum DC bus voltage (600 V) determines that the total impedance of the resistive divider is 6 MΩ. The impedance of the resistive divider is dominated by the top portion (shown exemplary as RX1 and RX2 in Figure 8-1) and the voltage drop across RSNS can be neglected for a moment. The maximum allowed voltage drop per unit resistor is specified as 100 V; therefore, the minimum number of unit resistors in the top portion of the resistive divider is 600 V / 100 V = 6. The calculated unit value is 6 MΩ / 6 = 1 MΩ and matches a value from the E96 series.

RSNS is sized such that the voltage drop across the resistor at the maximum DC-bus voltage (600 V) equals the linear full-scale range input voltage (VFSR) of the AMC1311-Q1, which is 2 V. The value of RSNS is calculated as RSNS = VFSR / (VDC-Bus, max – VFSR) × RTOP, where RTOP is the total value of the top resistor string (6 × 1 MΩ = 6 MΩ). RSNS is calculated as 20.07 kΩ. The next closest, lower value from the E96 series is 20 kΩ.

Table 8-2 summarizes the design of the resistive divider.

Table 8-2 Resistor Value Example
PARAMETER VALUE
Unit resistor value, RX 1 MΩ
Number of unit resistors 6
Sense resistor value, RSNS 20 kΩ
Total resistance value 6.02 MΩ
Resulting current through resistive divider, ICROSS 99.7 μA
Resulting full-scale voltage drop across sense resistor RSNS 1.993 V
Power dissipated in unit resistor RX 9.9 mW
Total power dissipated in resistive divider 59.8 mW