SBAS945A February   2022  – July 2022 AMC23C14

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 Reference Input
      3. 7.3.3 Isolation Channel Signal Transmission
      4. 7.3.4 Open-Drain Digital Outputs
      5. 7.3.5 Power-Up and Power-Down Behavior
      6. 7.3.6 VDD1 Brownout and Power-Loss Behavior
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Overcurrent and Short-Circuit Current Detection
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
      2. 8.2.2 Overvoltage and Undervoltage Detection
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
    3. 8.3 Best Design Practices
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
  9. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  10. 10Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.1.2 Detailed Design Procedure

The value of the shunt resistor in this example is 10 mΩ, determined by the linear input voltage range of the AMC1300B current-sensing amplifier (±250 mV) and the full-scale current of ±25 A. The short-circuit current detection threshold of the AMC23C14 is a fixed 300-mV value and places the short-circuit current threshold at 30 A.

At the desired 20-A overcurrent detection level, the voltage drop across the shunt resistor is 10 mΩ × 20 A = 200 mV. The positive-going trip threshold of window comparator 1 is VREF + VHYS, where VHYS is 4 mV as specified in the Electrical Characteristics table and VREF is the voltage across R1 that is connected between the REF and GND1 pins. R1 is calculated as (VTRIP – VHYS) / IREF = (200 mV – 4 mV) / 100 μA = 1.96 kΩ and matches a value from the E96 series (1% accuracy).

A 10-Ω, 1-nF RC filter (R5, C6) is placed at the input of the comparator to filter the input signal and reduce noise sensitivity. This filter adds 10 Ω × 1 nF = 10 ns of propagation delay that must be considered when calculating the overall response time of the protection circuit. Larger filter constants are preferable to increase noise immunity if the system can tolerate the additional delay.

Table 8-2 summarizes the key parameters of the design.

Table 8-2 Overcurrent and Short-Circuit Detection Design Example
PARAMETER VALUE
Reference resistor value (R1) 1.96 kΩ
Reference capacitor value (C5) 100 nF
Reference voltage 196 mV
Reference voltage settling time (to 90% of final value) 470 μs
Overcurrent trip threshold (rising) 200 mV / 20.0 A
Overcurrent trip threshold (falling) 196 mV / 19.6 A
Short-circuit current trip threshold (rising) 304 mV / 30.4 A
Short-circuit current trip threshold (falling) 300 mV / 30.0 A