SLVSCL3E June   2014  – May 2019 TPS65283 , TPS65283-1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Typical Schematic
    1.     Efficiency, Vin = 12 V, PSM
  5. 5 Revision History
  6. 6 Description (continued)
  7. 7 Pin Configuration and Functions
    1.     Pin Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 Handling Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Power Switch Detailed Description
        1. 9.3.1.1 Overcurrent Condition
        2. 9.3.1.2 Reverse Current and Voltage Protection
        3. 9.3.1.3 nFAULT Response
        4. 9.3.1.4 UVLO
        5. 9.3.1.5 Enable and Output Discharge
        6. 9.3.1.6 Power Switch Input and Output Capacitance
        7. 9.3.1.7 Programming the Current-Limit Threshold
      2. 9.3.2 Buck DC-DC Converter Detailed Description
        1. 9.3.2.1  Output Voltage
        2. 9.3.2.2  Adjustable Switching Frequency
        3. 9.3.2.3  Synchronization
        4. 9.3.2.4  Error Amplifier
        5. 9.3.2.5  Slope Compensation
        6. 9.3.2.6  Enable and Adjusting UVLO
        7. 9.3.2.7  Internal V7V Regulator
        8. 9.3.2.8  Short Circuit Protection
          1. 9.3.2.8.1 High-Side MOSFET Overcurrent Protection
          2. 9.3.2.8.2 Low-Side MOSFET Overcurrent Protection
        9. 9.3.2.9  Bootstrap Voltage (BST) and Low Dropout Operation
        10. 9.3.2.10 Output Overvoltage Protection (OVP)
        11. 9.3.2.11 Power Good
        12. 9.3.2.12 Power-Up Sequencing
        13. 9.3.2.13 Thermal Performance
    4. 9.4 Device Functional Modes
      1. 9.4.1 Operation With VIN < 4.5 V (Minimum VIN)
      2. 9.4.2 Operation With EN Control
      3. 9.4.3 Operation at Light Loads
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Output Voltage Setting
        2. 10.2.2.2 Bootstrap Capacitor Selection
        3. 10.2.2.3 Inductor Selection
        4. 10.2.2.4 Output Capacitor Selection
        5. 10.2.2.5 Input Capacitor Selection
        6. 10.2.2.6 Minimum Output Voltage
        7. 10.2.2.7 Compensation Component Selection
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 PCB Layout Recommendation
      2. 12.1.2 Power Dissipation and Junction Temperature
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Related Links
    2. 13.2 Trademarks
    3. 13.3 Electrostatic Discharge Caution
    4. 13.4 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

10.2.2.3 Inductor Selection

The higher operating frequency allows the use of smaller inductor and capacitor values. A higher frequency generally results in lower efficiency because of MOSFET gate charge losses. In addition to this basic trade-off, consider the effect of inductor value on ripple current and low current operation. The ripple current depends on the inductor value. The inductor ripple current iL decreases with higher inductance or higher frequency and increases with higher input voltage VIN. Accepting larger values of iL allows the use of low inductances, but results in higher output voltage ripple and greater core losses.

To calculate the value of the output inductor, use Equation 6. LIR is a coefficient that represents inductor peak-to-peak ripple to dc load current. LIR is suggested to choose to 0.1 to about 0.3 for most applications.

Actual core loss of inductor is independent of core size for a fixed inductor value, but it is very dependent on inductance value selected. As inductance increases, core losses go down. Unfortunately, increased inductance requires more turns of wire and therefore copper losses increase. Ferrite designs have very-low core loss and are preferred for high switching frequencies, so design goals can concentrate on copper loss and preventing saturation. Ferrite core material saturates hard, which means that inductance collapses abruptly when the peak design current is exceeded. It results in an abrupt increase in inductor ripple current and consequent output voltage ripple. Do not allow the core to saturate. It is important that the RMS current and saturation current ratings are not exceeding the inductor specification. Calculate the RMS and peak inductor current from Equation 8 and Equation 9.

Equation 6. TPS65283 TPS65283-1 Eq10_L_slvscl3.gif

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Equation 7. TPS65283 TPS65283-1 Eq11_delta_slvscl3.gif

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Equation 8. TPS65283 TPS65283-1 Eq12_iLrms_slvscl3.gif

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Equation 9. TPS65283 TPS65283-1 Eq13_ILp_slvscl3.gif

For this design example, use LIR = 0.3, and inductor is calculated to be 2.1 µH with Vin = 12 V, Vout = 1.2 V, Iout = 3.5 A. Choose 4.7-µH value of standard inductor, the peak-to-peak inductor ripple is about 13.1% of 3.5-A dc load current.