SLUSEY7B December   2022  – December 2024 TPSM82816

PRODMIX  

  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 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 Precise Enable (EN)
      2. 7.3.2 Output Discharge
      3. 7.3.3 COMP/FSET
      4. 7.3.4 MODE/SYNC
      5. 7.3.5 Spread Spectrum Clocking (SSC)
      6. 7.3.6 Undervoltage Lockout (UVLO)
      7. 7.3.7 Power-Good Output (PG)
      8. 7.3.8 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Pulse Width Modulation (PWM) Operation
      2. 7.4.2 Power Save Mode Operation (PSM)
      3. 7.4.3 100% Duty-Cycle Operation
      4. 7.4.4 Current Limit and Short-Circuit Protection
      5. 7.4.5 Soft Start / Tracking (SS/TR)
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Setting the Output Voltage
        2. 8.2.2.2 Feedforward Capacitor
        3. 8.2.2.3 Input Capacitor
        4. 8.2.2.4 Output Capacitor
      3. 8.2.3 Application Curves
    3. 8.3 System Examples
      1. 8.3.1 Voltage Tracking
      2. 8.3.2 Synchronizing to an External Clock
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
        1. 8.5.2.1 Thermal Consideration
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 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

7.4.4 Current Limit and Short-Circuit Protection

The TPSM8281x is protected against overload and short circuit events. If the inductor current exceeds the current limit ILIMH, the high-side MOSFET is turned off and the low-side MOSFET is turned on to ramp down the inductor current. The high-side MOSFET turns on again only if the current in the low-side MOSFET has decreased below the low-side current limit. Due to internal propagation delays, the actual current can exceed the static current limit. The dynamic current limit is given as:

Equation 6. Ipeak (typ)=ILIMH +VL L ×tPD

where

  • ILIMH is the static current limit, as specified in the electrical characteristics
  • L is the effective inductance
    • SIE: typically 220 nH
    • VCA (MagPack): typically 200 nH
  • VL is the voltage across the inductor (VIN - VOUT)
  • tPD is the internal propagation delay of typically 50 ns

The dynamic peak current is calculated as follows:

Equation 7. Ipeak (typ)=ILIMH +VIN- VOUT L ×50 ns
The low-side MOSFET also contains a negative current limit to prevent excessive current from flowing back through the inductor to the input. If the low-side sinking current limit is exceeded, the low-side MOSFET is turned off. In this scenario, both MOSFETs are off until the start of the next cycle. The negative current limit is only active in Forced PWM mode.