SLVSB76B August   2012  – August 2019 TPS63036

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Schematic
      2.      Efficiency vs Output Current
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Device Enable
      2. 7.3.2 Overvoltage Protection
      3. 7.3.3 Undervoltage Lockout
      4. 7.3.4 Overtemperature Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Soft-Start and Short Circuit Protection
      2. 7.4.2 Buck-Boost Operation
      3. 7.4.3 Control Loop
      4. 7.4.4 Power-Save Mode and Synchronization
  8. 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 Inductor Selection
        2. 8.2.2.2 Capacitor Selection
          1. 8.2.2.2.1 Input Capacitor
          2. 8.2.2.2.2 Output Capacitor
        3. 8.2.2.3 Setting the Output Voltage
        4. 8.2.2.4 Current Limit
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Considerations
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.4.3 Control Loop

The average inductor current is regulated by a fast current regulator loop which is controlled by a voltage control loop. Figure 3 shows the control loop.

The noninverting input of the trans-conductance amplifier Gmv can be assumed to be constant. The output of Gmv defines the average inductor current. The inductor current is reconstructed measuring the current through the high-side buck MOSFET. This current corresponds exactly to the inductor current in boost mode. In buck mode the current is measured during the ON-time of the same MOSFET. During the OFF-time the current is reconstructed internally starting from the peak value reached at the end of the ON-time cycle. The average current is then compared to the desired value and the difference, or current error, is amplified and compared to the sawtooth ramp of either the buck or the boost.

The Buck-Boost Overlap Control makes sure that the classical buck-boost function, which would cause two switches to be on every half a cycle, is avoided. Thanks to this block whenever all switches becomes active during one clock cycle, the two ramps are shifted away from each other, on the other hand when there is no switching activities because there is a gap between the ramps, the ramps are moved closer together. As a result the number of classical buck-boost cycles or no switching is reduced to a minimum and high-efficiency values have been achieved.

Slope compensation is not required to avoid subharmonic oscillation which are otherwise observed when working with peak current mode control with D > 0.5.

Nevertheless the amplified inductor current downslope at one input of the PWM comparator must not exceed the oscillator ramp slope at the other comparator input. This purpose is reached limiting the gain of the current amplifier.

TPS63036 fbd_lvs696.gifFigure 3. Average Current Mode Control