SLUSF22 November   2024 TPS54538

PRODUCTION DATA  

  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 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  Fixed Frequency Peak Current Mode
      2. 6.3.2  Mode Selection
      3. 6.3.3  Voltage Reference
      4. 6.3.4  Output Voltage Setting
      5. 6.3.5  Switching Frequency Selection / Synchronization
      6. 6.3.6  Phase Shift
      7. 6.3.7  Enable and Adjusting Undervoltage Lockout
      8. 6.3.8  External Soft Start and Prebiased Soft Start
      9. 6.3.9  Power Good
      10. 6.3.10 Minimum On Time, Minimum Off Time, and Frequency Foldback
      11. 6.3.11 Frequency Spread Spectrum
      12. 6.3.12 Overvoltage Protection
      13. 6.3.13 Overcurrent and Undervoltage Protection
      14. 6.3.14 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Modes Overview
      2. 6.4.2 Heavy Load Operation
      3. 6.4.3 Pulse Frequency Modulation
      4. 6.4.4 Forced Continuous Conduction Modulation
      5. 6.4.5 Dropout Operation
      6. 6.4.6 Minimum On-Time Operation
      7. 6.4.7 Shutdown Mode
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Custom Design With WEBENCH® Tools
        2. 7.2.2.2 Output Voltage Resistors Selection
        3. 7.2.2.3 Choosing Switching Frequency
        4. 7.2.2.4 Soft-Start Capacitor Selection
        5. 7.2.2.5 Output Inductor Selection
        6. 7.2.2.6 Output Capacitor Selection
        7. 7.2.2.7 Input Capacitor Selection
        8. 7.2.2.8 Feedforward Capacitor CFF Selection
        9. 7.2.2.9 Maximum Ambient Temperature
      3. 7.2.3 Application Curves
    3. 7.3 Best Design Practices
    4. 7.4 Power Supply Recommendations
    5. 7.5 Layout
      1. 7.5.1 Layout Guidelines
      2. 7.5.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Third-Party Products Disclaimer
      2. 8.1.2 Development Support
        1. 8.1.2.1 Custom Design With WEBENCH® Tools
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

6.1 Overview

The TPS54538 is a high efficiency, high voltage input, and easy-to-use synchronous buck converter with high design flexibility. With the wide operating input voltage range of 3.8V to 28V, the TPS54538 is designed for systems powered from 5V, 12V, 19V, 24V power-bus rails. The device supports up to 5A continuous output current and 98% maximum duty cycle.

TPS54538 uses peak current mode control with internal compensation for fast transient response and good line and load regulation. With the internal adaptive loop adjustment, the device eliminates the need for external compensation over a wide output voltage range and switching frequency. The integrated boostcap and the related circuit helps achieve single layer PCB and further reduce the external component count.

With different configuration of MODE pin, the device has option for pulse frequency modulation (PFM), forced continuous current modulation (FCCM) at light load condition and adjustable soft-start time / power-good indicator. When working at PFM mode, the device can attain high efficiency at light load. The FCCM mode helps TPS54538 have low output ripple in all load conditions. A small value capacitor or resistor divider is connected to the SS/PG pin for soft-start time setting or voltage tracking when the device is set to have SS function. When PG function is selected, the device can indicate power good through SS/PG pin.

The EN pin has an internal pullup current that can be used to adjust the input voltage undervoltage lockout (UVLO) with two external resistors. In addition, the EN pin can be floating for the device to operate with the internal pullup current.

The switching frequency can be set by the configuration of the RT/SYNC pin in the range of 200kHz to 2.2MHz, which allows for efficiency and design size optimization when selecting the output filter components. The frequency spread spectrum feature helps the device lower down EMI noise.

TPS54538 has the on-time extension function with a maximum on time of 8μs (typical). During low dropout operation, the high-side MOSFET can turn on up to 8μs, then the high-side MOSFET turns off and the low-side MOSFET turns on with a minimum off time of 114ns (typical). The devices support the maximum 98% duty cycle.

Cycle-by-cycle current limiting on the high-side MOSFET protects the device in overload situations and is enhanced by a low-side sourcing current limit, which prevents current runaway. The TPS54538 provides output undervoltage protection (UVP) when the regulated output voltage is lower than 65% of the nominal voltage due to overcurrent being triggered, approximately 256μs (typical) deglitch time later, both the high-side and low-side MOSFET turn off, the device steps into hiccup mode.

The devices minimize excessive output overvoltage transient by taking advantage of the overvoltage comparator. When the regulated output voltage is greater than 115% of the nominal voltage, the overvoltage comparator is activated, and the high-side MOSFET is turned off and keep off until the output voltage is lower than 104%.

Thermal shutdown disables the devices when the die temperature, TJ, exceeds 165°C and enables the devices again after TJ decreases below the hysteresis amount of 30°C.