SLVSHA1D September   2024  – July 2026 TPS1685

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 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 Electrical Characteristics
    6. 6.6 Logic Interface
    7. 6.7 Timing Requirements
    8. 6.8 Switching Characteristics
    9. 6.9 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Undervoltage Protection
      2. 7.3.2  Insertion Delay
      3. 7.3.3  Overvoltage Protection
      4. 7.3.4  Inrush Current, Overcurrent, and Short-Circuit Protection
        1. 7.3.4.1 Slew Rate (dVdt) and Inrush Current Control
          1. 7.3.4.1.1 Start-Up Time Out
        2. 7.3.4.2 Steady-State Overcurrent Protection (Circuit-Breaker)
        3. 7.3.4.3 Active Current Limiting During Start-Up
        4. 7.3.4.4 Short-Circuit Protection
      5. 7.3.5  Analog Load Current Monitor (IMON)
      6. 7.3.6  Mode Selection (MODE)
      7. 7.3.7  Parallel Device Synchronization (SWEN)
      8. 7.3.8  Stacking Multiple eFuses for Unlimited Scalability
        1. 7.3.8.1 Current Balancing During Start-Up
      9. 7.3.9  Analog Junction Temperature Monitor (TEMP)
      10. 7.3.10 Overtemperature Protection
      11. 7.3.11 Fault Response and Indication (FLT)
      12. 7.3.12 Power Good Indication (PG)
      13. 7.3.13 Output Discharge
      14. 7.3.14 FET Health Monitoring
      15. 7.3.15 Single Point Failure Mitigation
        1. 7.3.15.1 IMON Pin Single Point Failure
        2. 7.3.15.2 IREF Pin Single Point Failure
        3. 7.3.15.3 ITIMER Pin Single Point Failure
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Single Device, Standalone Operation
      2. 8.1.2 Multiple Devices, Parallel Connection
    2. 8.2 Typical Application: 54V Power Path Protection in Data Center Servers
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
      1. 8.3.1 Transient Protection and Other Design Considerations
      2. 8.3.2 Output Short-Circuit Measurements
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 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
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.4.1 Slew Rate (dVdt) and Inrush Current Control

During hot plug events or while trying to charge a large output capacitance, there can be a large inrush current. If the inrush current is not managed properly, the inrush current can damage the input connectors and cause the system power supply to droop. This action can lead to unexpected restarts elsewhere in the system. The inrush current during turn-on is directly proportional to the load capacitance and rising slew rate. Use Equation 3 to find the slew rate (SR) required to limit the inrush current (IINRUSH) for a given load capacitance (CLOAD):

Equation 3. SRV/ms=IINRUSHACLOADmF

Add a capacitor to the DVDT pin to control the rising slew rate and lower the inrush current during turn-on. Slew rate control using the DVDT pin holds true as long as the resulting startup current through the device is less than the Istart-up peak. The device limits the current at startup to not exceed Istart-up peak. Calculate the required CdVdt capacitance to produce a given slew rate using Equation 4.

Equation 4. CDVDTnF=48SRV/ms

Leave the dVdt pin open to achieve the fastest output slew rate.

Note:
  1. TI recommends using a minimum dvdt capacitor of 22nF.
  2. High input slew rates in combination with high input power path inductance can result in oscillations during start-up. Mitigate oscillations using one or more of the following steps:
    1. Reduce the input inductance.
    2. Increase the capacitance on VIN pin.
    3. Increase the dVdt pin capacitance to reduce the slew rate or increase the start-up time.