SBASB90 February   2025 AMC23C10-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  ESD Ratings
    3. 5.3  Recommended Operating Conditions
    4. 5.4  Thermal Information 
    5. 5.5  Power Ratings
    6. 5.6  Insulation Specifications (Reinforced Isolation)
    7. 5.7  Safety-Related Certifications 
    8. 5.8  Safety Limiting Values 
    9. 5.9  Electrical Characteristics 
    10. 5.10 Switching Characteristics 
    11. 5.11 Timing Diagrams
    12. 5.12 Insulation Characteristics Curves
    13. 5.13 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Analog Input
      2. 6.3.2 Isolation Channel Signal Transmission
      3. 6.3.3 Digital Outputs
      4. 6.3.4 Power-Up and Power-Down Behavior
      5. 6.3.5 VDD1 Brownout and Power-Loss Behavior
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Voltage Zero-Crossing Detection
      2. 7.2.2 Design Requirements
      3. 7.2.3 Detailed Design Procedure
      4. 7.2.4 Application Curves
    3. 7.3 Best Design Practices
    4. 7.4 Power Supply Recommendations
    5. 7.5 Layout
      1. 7.5.1 Layout Guidelines
      2. 7.5.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.2.3 Detailed Design Procedure

The value of shunt resistor R5 is determined by the maximum peak input voltage and the maximum allowed current. The maximum peak input voltage is 230VRMS × 1.1 × √2 = 360VPK and the maximum allowed current is 150μA. R5 is therefore calculated as 360VPK / 150μA = 2.4MΩ. Divide R5 into a minimum of five unit resistors of 480kΩ each to limit the maximum voltage drop per resistor to the allowed 75V. The closest value from the E96 series is 487kΩ and, therefore, the total R5 value is 5 × 487kΩ = 2.43MΩ.

The two diodes D1A and D1B have a forward-bias voltage from 200mV to 500mV at 150μA forward current, depending on temperature. Therefore, these diodes satisfy both the minimum required voltage swing and the maximum allowed input voltage at the INP pin.

The reverse-bias capacitance of D1A and D1B is 3pF (maximum). D1A, D1B, and R5 form an input filter with a corner frequency of less than 22.1kHz or a delay time of approximately 7.2μs (maximum). The corner frequency of the low-pass filter is adjusted down by inserting a small-value capacitor (C6). A larger filter capacitance is preferable to increase noise immunity if the system tolerates the additional delay. The total delay time of the zero-crossing detection is 7.2μs from the input filter plus the propagation delay of the comparator of 320ns (maximum). The slew rate of the AC line voltage during the zero crossing is 360VPK × 2 × π × 50Hz = 113mV/μs. The effective zero-crossing threshold therefore is 113mV/μs × (7.2μs + 320ns) = 850mV.

Table 7-2 summarizes the key parameters of the design.

Table 7-2 Zero-Crossing Detection Design Example
PARAMETER VALUE
Shunt resistor value R5 2.43MΩ (5 × 487kΩ)
Maximum current through R5 148μA
Effective switching threshold ±850mV
Propagation delay <8μs