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

2.2.7 Selecting the CITIMER Capacitor to Set the Overcurrent Blanking Timer

An appropriate capacitor must be connected at the ITIMER pin to ground of the primary or standalone device to adjust the duration for which the load transients above the circuit-breaker threshold are allowed. The transient overcurrent blanking interval can be calculated using Equation 17.

Equation 17. tITIMERms=CITIMERnF×∆VITIMERVIITIMERμA

where

  • tITIMER = the transient overcurrent blanking timer
  • CITIMER is the capacitor connected between the ITIMER pin of the primary device and GND
  • IITIMER = 2.07µA (typical)
  • ΔVITIMER = 1.5V (typical)

A 22nF capacitor with 10% tolerance and DC voltage rating of 25V is used as the CITIMER for the primary device in this design, which results in 16.5ms of tITIMER. Leave the ITIMER pin for all the secondary devices open.