TIDUF75 April   2025

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 System Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1  Determining the Number of eFuse Devices to use in Parallel
      2. 2.2.2  Setting up the Primary and Secondary Devices in a Parallel Configuration
      3. 2.2.3  Selecting the CDVDT Capacitor to Control the Output Slew Rate and Start-Up Time
      4. 2.2.4  Selecting the RIREF Resistor to set the Reference Voltage for Overcurrent Protection and Active Current Sharing
      5. 2.2.5  Selecting the RIMON Resistor to set the Overcurrent (Circuit Breaker) and Fast-Trip Thresholds During Steady-State
      6. 2.2.6  Selecting the RILIM Resistor to set the Current Limit and Fast-Trip Thresholds During Start-Up and the Active Sharing Threshold During Steady-State
      7. 2.2.7  Selecting the CITIMER Capacitor to Set the Overcurrent Blanking Timer
      8. 2.2.8  Selecting the Resistors to set the Under-voltage Lockout Threshold
      9. 2.2.9  Selecting the R-C Filter Between VIN and VDD
      10. 2.2.10 Selecting the Pullup Resistors and Power Supplies for SWEN, PG, FLT, and CMPOUT Pins
      11. 2.2.11 TVS Diode Selection at Input and Schottky Diode Selection at Output
      12. 2.2.12 Selecting CIN and COUT
    3. 2.3 Highlighted Products
      1. 2.3.1 TPS25985
      2. 2.3.2 LM94022 and LM94022-Q1
      3. 2.3.3 INA241x
      4. 2.3.4 TLV760
      5. 2.3.5 SN74LVC1G123
      6. 2.3.6 UCC27511A
      7. 2.3.7 CSD18510Q5B
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1.      36
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 Bill of Materials
      3. 4.1.3 Altium Project
      4. 4.1.4 Gerber Files
    2. 4.2 Tools
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Author

2.2.5 Selecting the RIMON Resistor to set the Overcurrent (Circuit Breaker) and Fast-Trip Thresholds During Steady-State

TPS25985x eFuse responds to the output overcurrent conditions during steady-state by turning off the output after a user-adjustable transient fault blanking interval. This eFuse continuously senses the total system current (IOUT) and produces a proportional analog current output (IIMON) on the IMON pin. This generates a voltage (VIMON) across the IMON pin resistor (RIMON) in response to the load current, which is defined as Equation 9.

Equation 9. VIMON=IOUT×GIMON×RIMON

GIMON is the current monitor gain (IIMON : IOUT), whose typical value is 18.18µA/A. The overcurrent condition is detected by comparing the VIMON against the VIREF as a threshold. The circuit-breaker threshold during steady-state (IOCP) can be calculated using Equation 10.

Equation 10. IOCP(TOTAL)=VIREFGIMON×RIMON

In the TIDA-050077, IOCP(TOTAL) is considered to be 1.1 times IOUT(max). Hence, IOCP(TOTAL) is set at 330A, and RIMON can be calculated to be 166.67Ω with GIMON as 18.18µA/A and VIREF as 1V. The nearest value of RIMON is 167Ω with 0.1% tolerance and a power rating of 100mW. For noise reduction, place a 22pF ceramic capacitor across the IMON pin and GND.

Note: A system output current (IOUT) must be considered when selecting RIMON, not the current carried by each device.