SLUSFL6A June   2024  – November 2024 TPSM82866C

PRODMIX  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Options
  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 I2C Interface Timing Characteristics
    7. 6.7 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 Power Save Mode
      2. 7.3.2 Forced PWM Mode
      3. 7.3.3 Optimized Transient Performance from PWM to PSM Operation
      4. 7.3.4 Low Dropout Operation (100% Duty Cycle)
      5. 7.3.5 Enable and Soft-Start Ramp
      6. 7.3.6 Switch Current Limit and HICCUP Short-Circuit Protection
      7. 7.3.7 Undervoltage Lockout
      8. 7.3.8 Thermal Warning and Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Enable and Disable (EN)
      2. 7.4.2 Output Discharge
      3. 7.4.3 Start-Up Output Voltage and I2C Target Address Selection (VSET)
      4. 7.4.4 Select Output Voltage Registers (VID)
    5. 7.5 Programming
      1. 7.5.1 Serial Interface Description
      2. 7.5.2 Standard-Mode, Fast-Mode, and Fast-Mode Plus Protocol
      3. 7.5.3 HS-Mode Protocol
      4. 7.5.4 I2C Update Sequence
      5. 7.5.5 I2C Register Reset
  9. 8 Register Map
    1. 8.1 Target Address Byte
    2. 8.2 Register Address Byte
    3. 8.3 VOUT Register 1
    4. 8.4 VOUT Register 2
    5. 8.5 CONTROL Register
    6. 8.6 STATUS Register
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Input and Output Capacitor Selection
      3. 9.2.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
        1. 9.4.2.1 Thermal Considerations
  11. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Third-Party Products Disclaimer
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Support Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

7.3.1 Power Save Mode

As the load current decreases, the device seamlessly enters power save mode (PSM) operation. In PSM, the converter operates with a reduced switching frequency and a minimum quiescent current to maintain high efficiency. Power save mode is based on a fixed on-time architecture, as shown in Equation 1. The inductance used in the TPSM8286xx is 200nH typical.

Equation 1. t O N = V O U T V I N ×   f S W

For very small output voltages, an absolute minimum on time of approximately 50ns is kept to limit switching losses. The operating frequency is thereby reduced from the nominal value, which keeps efficiency high. The switching frequency in PSM is estimated as:

Equation 2. f P S M = 2   ×   I O U T t O N 2 × V I N V O U T × V I N -   V O U T L

The load current at which PSM is entered is at one half of the ripple current of the inductor and can be estimated as:

Equation 3. I L o a d ( P S M - e n t r y ) = V I N × t O N 2 × 1 -   V O U T V I N L

In power save mode, the output voltage rises slightly above the nominal output voltage. This effect is minimized by increasing the output capacitance.