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

2.2.11 TVS Diode Selection at Input and Schottky Diode Selection at Output

When the device interrupts a large amount of current instantaneously causing a short circuit and overload current limit, the input inductance generates a positive voltage spike on the input, whereas the output inductance creates a negative voltage spike on the output. The peak amplitudes of these voltage spikes (transients) are dependent on the value of inductance in series with the input or output of the device. Such transients can exceed the absolute maximum ratings of the device and eventually lead to failures due to electrical over-stress (EOS) if appropriate steps are not taken to address this issue. Typical methods for addressing this issue include:

  1. Minimize lead length and inductance into and out of the device.
  2. Use a large PCB GND plane.
  3. Add TVS diodes to clamp the positive transient spike at the input.
  4. Use Schottky diodes across the output to absorb negative spikes.

See also TVS Clamping in Hot-Swap Circuits and Selecting TVS Diodes in Hot-Swap and ORing Applications for details on selecting an appropriate TVS diode and the number of TVS diodes to be in parallel to effectively clamp the positive transients at the input below the absolute maximum ratings of the IN pin (20V). These TVS diodes also help to limit the transient voltage at the IN pin during the Hot Plug event. Five (5) 5.0SMDJ12A are used in parallel in the TIDA-050077.

Note: Maximum Clamping Voltage (VC) specification of the selected TVS diode at Ipp (10/1000μs) (V) must be lower than the absolute maximum rating of the power input (IN) pin for safe operation of the eFuse.

Select Schottky diodes based on the following criteria:

  • The non-repetitive peak forward surge current (IFSM) of the selected diode must be more than the fast-trip threshold (2 × IOCP(TOTAL)). Two or more Schottky diodes in parallel must be used if a single Schottky diode is unable to meet the required IFSM rating. Equation 19 calculates the number of Schottky diodes (NSchottky) that must be in parallel.
    Equation 19. NSchottky>2×IOCPTOTALIFSM
  • Forward Voltage Drop (VF) at or near to IFSM must be as small as possible. For the best outcome, clamp the negative transient voltage at the OUT pin within the absolute maximum rating of the OUT pin (–1V).
  • DC Blocking Voltage (VRM) must be more than the maximum input operating voltage.
  • Leakage current (IR) must be as small as possible.

Five (5) PMEG045V100EPE-QZ devices are used in parallel in the TIDA-050077.