SBASAW1A September   2023  – December 2023 AMC21C12

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 Package Characteristics
    6. 5.6 Electrical Characteristics
    7. 5.7 Switching Characteristics 
    8. 5.8 Timing Diagrams
    9. 5.9 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 Reference Input
      3. 6.3.3 Isolation Channel Signal Transmission
      4. 6.3.4 Open-Drain Digital Output
        1. 6.3.4.1 Transparent Output Mode
        2. 6.3.4.2 Latch Output Mode
      5. 6.3.5 Power-Up and Power-Down Behavior
      6. 6.3.6 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 Applications
      1. 7.2.1 Overcurrent Detection
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Overvoltage Detection
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
        3. 7.2.2.3 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

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • DEN|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.2.1.2 Detailed Design Procedure

The value of the shunt resistor in this example is 10 mΩ and is determined by the target voltage drop at peak motor current (±250 mV at ±25 A). The ±250 mV is an arbitrary value but aligns well with the linear input voltage range of isolated current sensing amplifiers that can be used to measure the current across the same shunt resistor.

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 the window comparator 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 7-2 summarizes the key parameters of the design.

Table 7-2 Overcurrent 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 at power-up(1) 470 μs
Overcurrent trip threshold (rising) 200 mV / 20.0 A
Overcurrent trip threshold (falling) 196 mV / 19.6 A
(1) Settling time to 90% of final value. Determined by simulation. Settling time must be considered during power-up, as explained in the Reference Input section.