SLUSDO4B August   2020  – June 2022 TPS628510 , TPS628511 , TPS628512 , TPS628513

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Schematic
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Precise Enable (EN)
      2. 9.3.2 MODE / SYNC
      3. 9.3.3 Spread Spectrum Clocking (SSC)
      4. 9.3.4 Undervoltage Lockout (UVLO)
      5. 9.3.5 Power Good Output (PG)
      6. 9.3.6 Thermal Shutdown
    4. 9.4 Device Functional Modes
      1. 9.4.1 Pulse Width Modulation (PWM) Operation
      2. 9.4.2 Power Save Mode Operation (PWM/PFM)
      3. 9.4.3 100% Duty-Cycle Operation
      4. 9.4.4 Current Limit and Short Circuit Protection
      5. 9.4.5 Foldback Current Limit and Short Circuit Protection
      6. 9.4.6 Output Discharge
      7. 9.4.7 Soft Start / Tracking (SS/TR)
      8. 9.4.8 Input Overvoltage Protection
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Programming the Output Voltage
      2. 10.1.2 Inductor Selection
      3. 10.1.3 Capacitor Selection
        1. 10.1.3.1 Input Capacitor
        2. 10.1.3.2 Output Capacitor
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curves
    3. 10.3 System Examples
      1. 10.3.1 Voltage Tracking
      2. 10.3.2 Synchronizing to an External Clock
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Third-Party Products Disclaimer
    2. 13.2 Receiving Notification of Documentation Updates
    3. 13.3 Support Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

10.1.2 Inductor Selection

The TPS62851x is designed for a nominal 0.47-µH inductor with a switching frequency of typically 2.25 MHz. Larger values can be used to achieve a lower inductor current ripple but they can have a negative impact on efficiency and transient response. Smaller values than 0.47 µH cause a larger inductor current ripple which causes larger negative inductor current in forced PWM mode at low or no output current. For a higher or lower nominal switching frequency, the inductance must be changed accordingly. See Section 7.3 for details.

The inductor selection is affected by several effects like inductor ripple current, output ripple voltage, PWM-to-PFM transition point, and efficiency. In addition, the inductor selected has to be rated for appropriate saturation current and DC resistance (DCR). Equation 5 calculates the maximum inductor current.

Equation 5. GUID-4F0D3DC8-2030-435E-B616-2E7A317F2EC3-low.gif
Equation 6. GUID-F4CBEDD7-6AA3-4C6F-9A39-9E2168EE9DCA-low.gif

where

  • IL(max) is the maximum inductor current
  • ΔIL(max) is the peak-to-peak inductor ripple current
  • Lmin is the minimum inductance at the operating point
Table 10-1 Typical Inductors
TYPE INDUCTANCE [µH] CURRENT [A](1) FOR DEVICE NOMINAL SWITCHING FREQUENCY DIMENSIONS [LxBxH] mm MANUFACTURER(2)

DFE201210U-R47M

 0.47 µH, ±20% see data sheet TPS628510/511 / 512 2.25 MHz 2.0 x 1.2 x 1.0 Murata
DFE201210U-1R0M 1 µH, ±20% see data sheet TPS628510/511 / 512 2.25 MHz 2.0x 1.2 x 1.0

Murata

DFE201210U-R68

 0.68 µH, ±20% see data sheet TPS628510/511 / 512 2.25 MHz 2.0x 1.2 x 1.0 Murata
XEL3515-561ME 0.56 µH, ±20% 4.5 TPS628510/511 / 512 2.25 MHz 3.5 x 3.2 x 1.5 Coilcraft
XFL4015-701ME 0.70 µH, ±20%

3.3

 TPS628510/511 / 512 2.25 MHz 4.0 x 4.0 x 1.6 Coilcraft
XFL4015-471ME 0.47 µH, ±20% 3.5 TPS628510/511 / 512 2.25 MHz 4.0 x 4.0 x 1.6 Coilcraft
(1) Lower of IRMS at 20°C rise or ISAT at 20% drop.

Calculating the maximum inductor current using the actual operating conditions gives the minimum saturation current of the inductor needed. A margin of about 20% is recommended to add. A larger inductor value is also useful to get lower ripple current, but increases the transient response time and size as well.