SLVS843B December   2008  – May 2018 TPS650250

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Detailed Block Diagram
  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  Dissipation Ratings
    6. 6.6  Electrical Characteristics
    7. 6.7  Electrical Characteristics VDCDC1
    8. 6.8  Electrical Characteristics VDCDC2
    9. 6.9  Electrical Characteristics VDCDC3
    10. 6.10 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 Step-Down Converters, VDCDC1, VDCDC2 AND VDCDC3
      2. 7.3.2 Power Save Mode Operation
      3. 7.3.3 Soft Start
      4. 7.3.4 100% Duty Cycle Low Dropout Operation
      5. 7.3.5 Low Dropout Voltage Regulators
      6. 7.3.6 Undervoltage Lockout
      7. 7.3.7 PWRFAIL
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Typical Configuration For The Samsung Processor S3C6400-533MHz
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
        1. 8.2.3.1 Inductor Selection for the DCDC Converters
        2. 8.2.3.2 Output Capacitor Selection
        3. 8.2.3.3 Input Capacitor Selection
        4. 8.2.3.4 Output Voltage Selection
        5. 8.2.3.5 Voltage Change on VDCDC3
        6. 8.2.3.6 Vdd_alive Output
        7. 8.2.3.7 LDO1 and LDO2
        8. 8.2.3.8 Vcc-Filter
      4. 8.2.4 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 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.3.1 Inductor Selection for the DCDC Converters

The three converters operate with 2.2 µH output inductors. Larger or smaller inductor values can be used to optimize performance of the device for specific conditions. The selected inductor has to be rated for its DC resistance and saturation current. The DC resistance of the inductor influences directly the efficiency of the converter. Therefore, an inductor with the lowest DC resistance should be selected for the highest efficiency.

For a fast transient response, a 2.2 μH inductor in combination with a 22 μF output capacitor is recommended. For an output voltage above 2.8 V, an inductor value of 3.3 μH minimum is required. Lower values result in an increased output voltage ripple in PFM mode. The minimum inductor value is 1.5 μH, but an output capacitor of 22 μF minimum is needed in this case.

Equation 4 calculates the maximum inductor current under static load conditions. The saturation current of the inductor should be rated higher than the maximum inductor current as calculated with Equation 4. This is recommended because during heavy load transient the inductor current rises above the calculated value.

Equation 4. TPS650250 q4_delta_lvs774.gif

where

  • f = Switching frequency (2.25 MHz typical)
  • L = Inductor value
  • ΔIL = Peak-to-peak inductor ripple current
  • ILmax = Maximum inductor current

The highest inductor current occurs at maximum Vin.

Open core inductors have a soft saturation characteristic and they can usually handle higher inductor currents versus a comparable shielded inductor.

A more conservative approach is to select the inductor current rating just for the maximum switch current of the corresponding converter. Consideration must be given to the difference in the core material from inductor to inductor which has an impact on efficiency especially at high switching frequencies. See Table 4 and the typical applications for possible inductors.

Table 4. Tested Inductors

DEVICE INDUCTOR
VALUE		 TYPE COMPONENT
SUPPLIER
DCDC3 Converter 3.3 μH LPS3015-332 (output current up to 1 A) Coilcraft
2.2 μH LPS3015-222 (output current up to 1 A) Coilcraft
3.3 μH VLCF4020T-3R3N1R5 TDK
2.2 μH VLCF4020T-2R2N1R7 TDK
DCDC3 Converter 2.2 μH LPS3010-222 Coilcraft
2.2 μH LPS3015-222 Coilcraft
2.2 μH VLCF4020-2R2 TDK