SLVSHO1 March   2025 TPS1689

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  ESD Ratings
    3. 5.3  Recommended Operating Conditions
    4. 5.4  Thermal Information
    5. 5.5  Electrical Characteristics
    6. 5.6  PMBus and GPIO DC Characteristics
    7. 5.7  Telemetry
    8. 5.8  Logic Interface
    9. 5.9  Timing Requirements
    10. 5.10 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  Undervoltage Protection
      2. 6.3.2  Insertion Delay
      3. 6.3.3  Overvoltage Protection
      4. 6.3.4  Inrush Current, Overcurrent, and Short-Circuit Protection
        1. 6.3.4.1 Slew rate (dVdt) and Inrush Current Control
          1. 6.3.4.1.1 Start-Up Timeout
        2. 6.3.4.2 Steady-State Overcurrent Protection (Circuit-Breaker)
        3. 6.3.4.3 Active Current Limiting During Start-Up
        4. 6.3.4.4 Short-Circuit Protection
      5. 6.3.5  Analog Load Current Monitor (IMON)
      6. 6.3.6  Overtemperature Protection
      7. 6.3.7  Analog Junction Temperature Monitor (TEMP)
      8. 6.3.8  FET Health Monitoring
      9. 6.3.9  Single Point Failure Mitigation
        1. 6.3.9.1 IMON Pin Single Point Failure
        2. 6.3.9.2 IREF Pin Single Point Failure
      10. 6.3.10 General Purpose Digital Input/Output Pins
        1. 6.3.10.1 Fault Response and Indication (FLT)
        2. 6.3.10.2 Power Good Indication (PG)
        3. 6.3.10.3 Parallel Device Synchronization (SWEN)
      11. 6.3.11 Stacking Multiple eFuses for Unlimited Scalability
        1. 6.3.11.1 Current Balancing During Start-Up
      12. 6.3.12 Quick Output Discharge(QOD)
      13. 6.3.13 Write Protect Feature(WP#)
      14. 6.3.14 PMBus® Digital Interface
        1. 6.3.14.1  PMBus® Device Addressing
        2. 6.3.14.2  SMBus Protocol
        3. 6.3.14.3  SMBus™ Message Formats
        4. 6.3.14.4  Packet Error Checking
        5. 6.3.14.5  Group Commands
        6. 6.3.14.6  SMBus™ Alert Response Address (ARA)
        7. 6.3.14.7  PMBus® Commands
        8. 6.3.14.8  Analog-to-digital Converter
        9. 6.3.14.9  Digital-to-analog Converters
        10. 6.3.14.10 DIRECT format Conversion
        11. 6.3.14.11 Blackbox Fault Recording
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Single Device, Standalone Operation
      2. 7.1.2 Single TPS1689 and multiple TPS1685 Devices, Parallel Connection
      3. 7.1.3 Multiple TPS1689 Devices: Parallel Connection With Individual Telemetry
      4. 7.1.4 Multiple Devices, Independent Operation (Multi-zone)
    2. 7.2 Typical Application: 54-V, 2-kW Power Path Protection with PMBus® Interface in Datacenter Servers
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
      3. 7.2.3 Application Performance Plots
    3. 7.3 Power Supply Recommendations
      1. 7.3.1 Transient Protection
      2. 7.3.2 Output Short-Circuit Measurements
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Application Limitation and Errata
  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
    1. 11.1 Mechanical Data

Package Options

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

6.3.4.1 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, it can put excessive stress on the system power supply causing it to droop and even damage the input connectors. 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. Equation 2 can be used to find the slew rate (SR) required to limit the inrush current (IINRUSH) for a given load capacitance (CLOAD):

Equation 2. S R   V m s = I I N R U S H   ( m A ) C O U T   µ F

A capacitor can be added to the DVDT pin to control the rising slew rate and lower the inrush current during turn-on. This is also a function of the dVdt rate scaling factor which can be digitally programmed through PMBus® writes to the DEVICE_CONFIGregister. The required CdVdt capacitance to produce a given slew rate can be calculated using Equation 3.

Equation 3. C d V d t   p F = 50000   ×   k S R   V m s

where k = 0.25, if DEVICE_CONFIG[10:9] = 00 (Default)

k = 0.5, if DEVICE_CONFIG[10:9] = 01

k = 1, if DEVICE_CONFIG[10:9] = 10

k = 1.5, if DEVICE_CONFIG[10:9] = 11

The fastest output slew rate is achieved by leaving the dVdt pin open and setting DEVICE_CONFIG[10:9] = 11.

The slew rate is also a function of the energy dissipated during start-up. The slew rate control via DVDT is only below the Start-up current limit IStartup. The current will be clamped at Istartup if the start-up current due to dvdt pin exceeds it and the slew rate will be slower

Note: High turn-on slew rates in combination with high input power path inductance can result in oscillations during start-up. This can be mitigated 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 capacitor value or change the DVDT scaling factor using DEVICE_CONFIG[10:9] register bits to reduce the slew rate or increase the start-up time. TI recommends using a minimum start-up time of 30 ms.