SLVSHR6A July   2025  – November 2025 TPS1686

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  Switch Enable Pin (SWEN)
      7. 7.3.7  Analog Junction Temperature Monitor (TEMP)
      8. 7.3.8  Overtemperature Protection
      9. 7.3.9  Fault Response and Indication (FLT)
      10. 7.3.10 Power Good Indication (PG)
      11. 7.3.11 Output Discharge
      12. 7.3.12 FET Health Monitoring
      13. 7.3.13 Single Point Failure Mitigation
        1. 7.3.13.1 IMON Pin Single Point Failure
        2. 7.3.13.2 IREF Pin Single Point Failure
        3. 7.3.13.3 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. 8.2 Typical Application: 54V Fan Load Protection in Datacenter Servers
      1. 8.2.1 Application
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
      4. 8.2.4 Application Performance Plots
    3. 8.3 Power Supply Recommendations
      1. 8.3.1 Transient Protection
      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 Third-Party Products Disclaimer
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.4.2 Steady-State Overcurrent Protection (circuit-breaker)

The TPS1686x responds to output overcurrent conditions during steady-state by performing a circuit-breaker action after a user-adjustable transient fault blanking interval. This action allows the device to support a higher peak current for a short user-defined interval but also provides robust protection in case of persistent output faults.

The device constantly senses the output load current and provides an analog current output (IIMON) on the IMON pin which is proportional to the load current, which in turn produces a proportional voltage (VIMON) across the IMON pin resistor (RIMON) as per Equation 4.

Equation 4. V I M O N = I O U T × G I M O N × R I M O N

Where GIMON is the current monitor gain (IIMON : IOUT)

The overcurrent condition is detected by comparing this voltage against the voltage on the IREF pin as a reference. The reference voltage (VIREF) can be controlled in two ways, which sets the overcurrent protection threshold (IOCP) accordingly.

  • The internal current source interacts with the external IREF pin resistor (RIREF) to generate the reference voltage. Driving the IREF pin from an external low impedance reference voltage source as shown in Equation 5 is also possible.
    Equation 5. V I R E F = I I R E F × R I R E F

The overcurrent protection threshold during steady-state (IOCP) can be calculated using Equation 6.

Equation 6. I O C P = V I R E F G I M O N × R I M O N

After an overcurrent condition is detected, that is the load current exceeds the programmed current limit threshold (IOCP), but stays lower than the short-circuit threshold (ISFT), the device starts discharging the ITIMER pin capacitor using an internal pulldown current. If the load current drops below the current limit threshold before the ITIMER capacitor discharges by ΔVITIMER, the ITIMER is reset by pulling the voltage up to VINT internally and the circuit-breaker action is not engaged. This action allows short overload transient pulses to pass through the device without tripping the circuit. If the overcurrent condition persists, the ITIMER capacitor continues to discharge and after the capacitor falls by ΔVITIMER, the circuit-breaker action turns off the FET immediately. At the same time, the ITIMER capacitor is charged up to VINT again so that the capacitor is at the default state before the next overcurrent event. This action verifies the full blanking timer interval is provided for every overcurrent event. Equation 7 can be used to calculate the RIMON value for the desired overcurrent threshold.

Equation 7. R I M O N = V I R E F G I M O N × I O C P

The duration for which transients are allowed can be adjusted using an appropriate capacitor value from ITIMER pin to ground. The transient overcurrent blanking interval can be calculated using Equation 8.

Equation 8. t I T I M E R m s = C I T I M E R n F × ∆ V I T I M E R V I I T I M E R μ A
Note:

  1. Leave the ITIMER pin open to allow the part to break the circuit with the minimum possible delay. However, this makes the circuit-breaker response extremely sensitive to noise and can cause false tripping during load transients.

  2. Shorting the ITIMER pin to ground results in minimum overcurrent response delay (similar to ITIMER pin open condition), but increases the quiescent current – not a recommended mode of operation.

  3. Increasing the ITIMER capacitor value extends the overcurrent blanking interval. However, this value also extends the time needed for the ITIMER capacitor to recharge up to VINT before the next overcurrent event. If the next overcurrent event occurs before the ITIMER capacitor is recharged fully, less time is taken to discharge to the VITIMER threshold, thereby providing a shorter blanking interval than intended.

Figure 7-3 illustrates the overcurrent response for TPS1686x eFuse. After the part shuts down due to a circuit-breaker fault, the device either stays latched off (TPS16860 variant) or restarts automatically after a fixed delay (TPS16861 variant).

TPS1686 Steady-State Overcurrent (Circuit-Breaker) ResponseFigure 7-3 Steady-State Overcurrent (Circuit-Breaker) Response