SLVSHR9 December   2024 TPS25984B

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  Digital Overcurrent Indication (D_OC)
      8. 7.3.8  Stacking Multiple eFuses for 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 (GOK/FLT)
      12. 7.3.12 Power-Good Indication (PG)
      13. 7.3.13 Output Discharge
      14. 7.3.14 FET Health Monitoring
    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
      3. 8.1.3 Digital Telemetry Using External Microcontroller
    2. 8.2 Typical Application: 12V, 3.3kW Power Path Protection in Data Center Servers
      1. 8.2.1 Application
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
      4. 8.2.4 Application Curves
    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 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

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.4.3 Active Current Limiting During Start-Up

The TPS25984Bx responds to output overcurrent conditions during start-up by actively limiting the current. The device constantly senses the current flowing through each one (IDEVICE) and provides an analog current output (IILIM) on the ILIM pin, which in turn produces a proportional voltage (VILIM) across the ILIM pin resistor (RILIM) as per Equation 9.

Equation 9. VILIM=IDEVICE×GILIM×RILIM

Where GILIM is the current monitor gain (IILIM : IDEVICE)

The overcurrent condition is detected by comparing this voltage against a threshold which is a scaled voltage (CLREFSAT) derived from the reference voltage (VIREF) on the IREF pin as presented in Equation 30.

Equation 10. CLREFSAT=0.4×VIREF

The reference voltage (VIREF) can be controlled in two ways, which sets the start-up current limit threshold (ILIM) accordingly.

  1. In the standalone mode of operation, the internal current source interacts with the external IREF pin resistor (RIREF) to generate the reference voltage as shown in Equation 11.
    Equation 11. VIREF=IIREF×RIREF

The active current limit (ILIM) threshold during start-up can be calculated using Equation 12.

Equation 12. IILIM=CLREFSATGILIM×RILIM

When the load current through the device during start-up exceeds ILIM, the device tries to regulate and hold the load current at ILIM.

During current regulation, the output voltage drops, resulting in increased device power dissipation across the FET. If the device internal temperature (TJ) exceeds the thermal shutdown threshold (TSD), the FET is turned off. After the part shuts down due to a TSD fault, it either stays latched off (TPS25984B2 variant with MODE pin floating or TPS25984B0/3 variants) or restarts automatically after a fixed delay (TPS25984B2 variant with MODE pin connected to GND or TPS25984B1 variant). See Overtemperature protection section for more details on device response to overtemperature.

Note:

The active current limit block employs a foldback mechanism during start-up based on the output voltage (VOUT). When VOUT is below the foldback threshold (VFB), the current limit threshold is further lowered.