SLVS763E June   2007  – July 2015 TPS62260 , TPS62261 , TPS62262 , TPS62263

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
  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. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Dynamic Voltage Positioning
      2. 8.3.2 Undervoltage Lockout
      3. 8.3.3 Mode Selection
      4. 8.3.4 Enable
      5. 8.3.5 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Soft-Start
      2. 8.4.2 Power Save Mode
      3. 8.4.3 100% Duty Cycle Low Dropout Operation
      4. 8.4.4 Short-Circuit Protection
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Output Voltage Setting
        2. 9.2.2.2 Output Filter Design (Inductor and Output Capacitor)
          1. 9.2.2.2.1 Inductor Selection
          2. 9.2.2.2.2 Output Capacitor Selection
          3. 9.2.2.2.3 Input Capacitor Selection
      3. 9.2.3 Application Curves
    3. 9.3 System Examples
      1. 9.3.1 TPS62260, Adjustable 1.5-V Output
      2. 9.3.2 TPS62262, Fixed 1.2-V Output
      3. 9.3.3 TPS62261, Fixed 1.8-V Output
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Examples
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Related Links
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

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9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

9.1 Application Information

The TPS6226x device is a high-efficiency synchronous step-down DC/DC converter featuring power save mode or 2.25 MHz fixed frequency operation.

9.2 Typical Application

TPS62260 TPS62261 TPS62262 TPS62263 ai_adj_lvs763.gifFigure 6. TPS62260DRV Adjustable 1.2-V Output

9.2.1 Design Requirements

The device operates over an input voltage range from 2 V to 6 V. The output voltage is adjustable using an external feedback divider.

9.2.2 Detailed Design Procedure

Table 1. List of Components

COMPONENT REFERENCE PART NUMBER MANUFACTURER VALUE
CIN GRM188R60J475K Murata 4.7 μF, 6.3 V. X5R Ceramic
COUT GRM188R60J106M Murata 10 μF, 6.3 V. X5R Ceramic
C1 Murata 22 pF, COG Ceramic
L1 LPS3015 Coilcraft 2.2 μH, 110 mΩ
R1, R2 Values depending on the programmed output voltage

9.2.2.1 Output Voltage Setting

The output voltage can be calculated to:

TPS62260 TPS62261 TPS62262 TPS62263 inl1_vout_lvs763.gifwith an internal reference voltage VREF typical 0.6 V.

To minimize the current through the feedback divider network, R2 should be 180 kΩ or 360 kΩ. The sum of R1 and R2 should not exceed ~1 MΩ, to keep the network robust against noise.

An external feed forward capacitor C1 is required for optimum load transient response. The value of C1 should be in the range between 22 pF and 33 pF.

Route the FB line away from noise sources, such as the inductor or the SW line.

9.2.2.2 Output Filter Design (Inductor and Output Capacitor)

The TPS6226x is designed to operate with inductors in the range of 1.5 μH to 4.7 μH and with output capacitors in the range of 4.7 μF to 22 μF. The part is optimized for operation with a 2.2-μH inductor and 10-μF output capacitor.

Larger or smaller inductor values can be used to optimize the performance of the device for specific operation conditions. For stable operation, the L and C values of the output filter may not fall below 1-μH effective inductance and 3.5-μF effective capacitance.

Selecting larger capacitors is less critical because the corner frequency of the L-C filter moves to lower frequencies with fewer stability problems.

9.2.2.2.1 Inductor Selection

The inductor value has a direct effect on the ripple current. The selected inductor has to be rated for its DC resistance and saturation current. The inductor ripple current (ΔIL) decreases with higher inductance and increases with higher VIN or VOUT.

The inductor selection also has an impact on the output voltage ripple in the PFM mode. Higher inductor values will lead to lower output voltage ripple and higher PFM frequency, lower inductor values will lead to a higher output voltage ripple but lower PFM frequency.

Equation 2 calculates the maximum inductor current in PWM mode under static load conditions. The saturation current of the inductor should be rated higher than the maximum inductor current as calculated with Equation 3. This is recommended because during heavy load transient the inductor current will rise above the calculated value.

Equation 2. TPS62260 TPS62261 TPS62262 TPS62263 q3_delta_lvs763_.gif

where

  • f = Switching frequency (2.25-MHz typical)
  • L = Inductor value
  • ΔIL = Peak-to-peak inductor ripple current
Equation 3. TPS62260 TPS62261 TPS62262 TPS62263 q4_ilmax_lvs763.gif

where

  • ΔIL = Peak-to-peak inductor ripple current
  • ILmax = Maximum inductor current

A more conservative approach is to select the inductor current rating just for the maximum switch current limit ILIMF of the converter.

Accepting larger values of ripple current allows the use of lower inductance values, but results in higher output voltage ripple, greater core losses, and lower output current capability.

The total losses of the coil have a strong impact on the efficiency of the DC/DC conversion and consist of both the losses in the dc resistance (R(DC)) and the following frequency-dependent components:

  • The losses in the core material (magnetic hysteresis loss, especially at high switching frequencies)
  • Additional losses in the conductor from the skin effect (current displacement at high frequencies)
  • Magnetic field losses of the neighboring windings (proximity effect)
  • Radiation losses

Table 2. List of Inductors

DIMENSIONS [mm3] Inductance μH INDUCTOR TYPE SUPPLIER
2.5 × 2.0 × 1.0 max 2.0 MIPS2520D2R2 FDK
2.5 × 2.0 ×1.2 max 2.0 MIPSA2520D2R2 FDK
2.5 × 2.0 × 1.0 max 2.2 KSLI-252010AG2R2 Htachi Metals
2.5 ×2.0 × 1.2 max 2.2 LQM2HPN2R2MJ0L Murata
3 × 3 × 1.5 max 2.2 LPS3015 2R2 Coilcraft

9.2.2.2.2 Output Capacitor Selection

The advanced fast-response voltage mode control scheme of the TPS6226x allows the use of tiny ceramic capacitors. Ceramic capacitors with low ESR values have the lowest output voltage ripple and are recommended. The output capacitor requires either an X7R or X5R dielectric. Y5V and Z5U dielectric capacitors, aside from their wide variation in capacitance over temperature, become resistive at high frequencies.

At nominal load current, the device operates in PWM mode and the RMS ripple current is calculated as:

Equation 4. TPS62260 TPS62261 TPS62262 TPS62263 q5_irmsc_lvs763.gif

At nominal load current, the device operates in PWM mode and the overall output voltage ripple is the sum of the voltage spike caused by the output capacitor ESR plus the voltage ripple caused by charging and discharging the output capacitor:

Equation 5. TPS62260 TPS62261 TPS62262 TPS62263 q6_deltav_lvs763.gif

At light load currents, the converter operates in power save mode and the output voltage ripple is dependent on the output capacitor and inductor value. Larger output capacitor and inductor values minimize the voltage ripple in PFM mode and tighten DC output accuracy in PFM mode.

9.2.2.2.3 Input Capacitor Selection

An input capacitor is required for best input voltage filtering, and minimizing the interference with other circuits caused by high input voltage spikes. For most applications, a 4.7-μF to 10-μF ceramic capacitor is recommended. Because ceramic capacitor loses up to 80% of its initial capacitance at 5 V, it is recommended that 10-μF input capacitors be used for input voltages >4.5 V. The input capacitor can be increased without any limit for better input voltage filtering. Take care when using only small ceramic input capacitors. When a ceramic capacitor is used at the input and the power is being supplied through long wires, such as from a wall adapter, a load step at the output or VIN step on the input can induce ringing at the VIN pin. This ringing can couple to the output and be mistaken as loop instability or could even damage the part by exceeding the maximum ratings.

Table 3. List of Capacitors

CAPACITANCE TYPE SIZE SUPPLIER
4.7 μF GRM188R60J475K 0603 1.6 × 0.8 × 0.8 mm3 Murata
10 μF GRM188R60J106M69D 0603 1.6 × 0.8 × 0.8 mm3 Murata

Table 1 shows the list of components for the Application Curves.

9.2.3 Application Curves

TPS62260 TPS62261 TPS62262 TPS62263 eff_18_gnd_lvs763.gifFigure 7. Efficiency (Power Save Mode) vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 eff_33_vin_lvs763.gifFigure 9. Efficiency (PWM Mode) vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 eff_12v_vin_lvs763.gifFigure 11. Efficiency vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 voacc1_25c_lvs763.gifFigure 13. Output Voltage Accuracy vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 voacc3_85c_lvs763.gifFigure 15. Output Voltage Accuracy (Power Save Mode) vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 voacc5_40c_lvs763.gifFigure 17. Output Voltage Accuracy (PWM Mode) vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 tc_pwm18_lvs763.gifFigure 19. Typical Operation (PWM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 tc_tr_pfpw_lvs763.gifFigure 21. Mode Pin Transition from PFM
to Forced PWM Mode at Light Load
TPS62260 TPS62261 TPS62262 TPS62263 tc_st_vo18_lvs763.gifFigure 23. Start-Up Timing
TPS62260 TPS62261 TPS62262 TPS62263 tc_fpwm2_lvs763.gifFigure 25. Load Transient (Forced PWM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 tc_pfm2f_lvs763.gifFigure 27. Load Transient (PWM Mode to PFM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 tc_pflotr2_lvs763.gifFigure 29. Load Transient (PFM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 tc_pflotr4_lvs763.gifFigure 31. Load Transient (PFM Mode to PWM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 tc_litr1_lvs763.gifFigure 33. Line Transient (PFM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 eff_18_vin_lvs763.gifFigure 8. Efficiency (PWM Mode) vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 eff_33_gnd_lvs763.gifFigure 10. Efficiency (Power Save Mode) vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 eff_12v_gnd_lvs763.gifFigure 12. Efficiency vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 voacc2_40c_lvs763.gifFigure 14. Output Voltage Accuracy (Power Save Mode) vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 voacc4_25c_lvs763.gifFigure 16. Output Voltage Accuracy (PWM Mode) vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 voacc6_85c_lvs763.gifFigure 18. Output Voltage Accuracy (PWM Mode) vs Output Current
TPS62260 TPS62261 TPS62262 TPS62263 tc_pfm18_lvs763.gifFigure 20. Typical Operation (PFM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 tc_tr_pwpf_lvs763.gifFigure 22. Mode Pin Transition from PWM
to PFM Mode at Light Load
TPS62260 TPS62261 TPS62262 TPS62263 tc_fpwm1_lvs763.gifFigure 24. Load Transient (Forced PWM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 tc_pfm1_lvs763.gifFigure 26. Load Transient (PFM Mode to PWM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 tc_pflotr1_lvs763.gifFigure 28. Load Transient (PFM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 tc_pflotr3_lvs763.gifFigure 30. Load Transient (PFM Mode to PWM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 tc_pflotr5_lvs763.pngFigure 32. Load Transient (PWM Mode to PFM Mode)
TPS62260 TPS62261 TPS62262 TPS62263 tc_litr2_lvs763.gifFigure 34. Line Transient (Forced PWM Mode)

9.3 System Examples

9.3.1 TPS62260, Adjustable 1.5-V Output

TPS62260 TPS62261 TPS62262 TPS62263 ai_adj15_lvs763.gifFigure 35. TPS62260 Adjustable 1.5-V Output

9.3.2 TPS62262, Fixed 1.2-V Output

TPS62260 TPS62261 TPS62262 TPS62263 ai_fix12_lvs763.gifFigure 36. TPS62262 Fixed 1.2-V Output

9.3.3 TPS62261, Fixed 1.8-V Output

TPS62260 TPS62261 TPS62262 TPS62263 ai_fix18_lvs763.gifFigure 37. TPS62261 Fixed 1.8-V Output