SLVSFE7 November   2019 TPS61391

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Circuit
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Recommended Operating Conditions
    2. 6.2 Absolute Maximum Ratings
    3. 6.3 ESD Ratings
    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 Undervoltage Lockout
      2. 7.3.2 Enable and Disable
      3. 7.3.3 Current Mirror
      4. 7.3.4 High Optical Power Protection
    4. 7.4 Device Functional Mode
      1. 7.4.1 PFM Operation
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirement
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Selecting the Rectifier Diode
        2. 8.2.2.2  Selecting the Inductor
        3. 8.2.2.3  Selecting Output Capacitor
        4. 8.2.2.4  Selecting Filter Resistor and Capacitor
        5. 8.2.2.5  Setting the Output Voltage
        6. 8.2.2.6  Selecting Capacitor for CAP pin
        7. 8.2.2.7  Selecting Capacitor for AVCC pin
        8. 8.2.2.8  Selecting Capacitor for APD pin
        9. 8.2.2.9  Selecting the Resistors of MON1 or MON2
        10. 8.2.2.10 Selecting the Capacitors of MON1 or MON2
        11. 8.2.2.11 Selecting the Short 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
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Package Option Addendum
      1. 12.1.1 Packaging Information
      2. 12.1.2 Tape and Reel Information

Package Options

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

8.2.2.2 Selecting the Inductor

It is suggested that the TPS61391 device works in the DCM operation; otherwise the output voltage would not be delivered for low input voltage to high output voltage.

With the device working in DCM operation, the maximum inductor could be calculated by equation Equation 1 and Equation 2:

Equation 1. TPS61391 eq_Lmax_SLVSEL7.gif

where

  • VIN is input voltage
  • D is duty cycle
  • fSW is switching frequency
  • ILIM is current limit

For instance, if VIN = 3.3 V, VOUT = 60 V, fSW = 600 kHz, ILIM = 0.8 A, the LMAX = 6.5 µH

However, there is minimum inductance is determined by the power delivered to the output side at given input condition.

Equation 2. TPS61391 eq_Lmin_SLVSEL7.gif

where

  • VOUT is output voltage
  • IOUT is output current
  • eff is the efficiency
  • fSW is switching frequency
  • ILIM is current limit

For instance, if IOUT = 8 mA, VOUT = 60 V, fSW = 600 kHz, ILIM = 0.8 A, eff = 0.6, the LMIN = 4.2 µH

With the calculation aforementioned, the operating inductor is recommended between the LMIN and LMAX.

The 4.7 µH inductance is optimum value for using the TPS61391 in application.