SLVSAE4A July   2010  – August 2014 TPS53128

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings
    3. 6.3 Recommended Operating Conditions
    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
      1. 7.2.1 16
      2. 7.2.2 17
    3. 7.3 Feature Description
      1. 7.3.1  PWM Operation
      2. 7.3.2  Light-Load Condition
      3. 7.3.3  Drivers
      4. 7.3.4  PWM Frequency And Adaptive On-Time Control
      5. 7.3.5  5-Volt Regulator
      6. 7.3.6  Soft Start
      7. 7.3.7  Pre-Bias Support
      8. 7.3.8  Output Discharge Control
      9. 7.3.9  Over Current Limit
      10. 7.3.10 Over/Under Voltage Protection
      11. 7.3.11 UVLO Protection
      12. 7.3.12 Thermal Shutdown
    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 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      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 Trademarks
    2. 11.2 Electrostatic Discharge Caution
    3. 11.3 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ

8 Application and Implementation

8.1 Application Information

8.2 Typical Application

TPS53128 qfn_app_digrm_lvsae4.gif Figure 10. QFN
TPS53128 tssop_app_digrm_lvsae4.gif Figure 11. TSSOP

8.2.1 Design Requirements

Table 3. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
Input Voltage 12 V
Output Voltage

Vo1 = 1.8 V

Vo2 = 1.05 V

8.2.2 Detailed Design Procedure

  1. Choose inductor.

    2. The inductance value is selected to provide approximately 30% peak to peak ripple current at maximum load. Larger ripple current increases output ripple voltage, improve S/N ratio and contribute to stable operation.

    Equation 4 can be used to calculate L1.

    Equation 4. TPS53128 eq4_L1_lvsae4.gif

    The inductors current ratings needs to support both the RMS (thermal) current and the Peak (saturation) current. The RMS and peak inductor current can be estimated as follows.

    Equation 5. TPS53128 eq4a_lvs947.gif
    Equation 6. TPS53128 eq5a_lvs947.gif
    Equation 7. TPS53128 eq6a_lvs947.gif

    Note: The calculation above shall serve as a general reference. To further improve transient response, the output inductance could be reduced further. This needs to be considered along with the selection of the output capacitor.

  2. Choose output capacitor.

    3. The capacitor value and ESR determines the amount of output voltage ripple and load transient response. it is recommended to use a ceramic output capacitor.

    Equation 8. TPS53128 eq7a_lvs947.gif
    Equation 9. TPS53128 eq8a_lvs947.gif
    Equation 10. TPS53128 eq9b_lvs947.gif

    Where

    Equation 11. TPS53128 eq10a_lvs947.gif

    Select the capacitance value greater than the largest value calculated from Equation 8, Equation 9 and Equation 10. The capacitance for C1 should be greater than 66 μF.

    Where

    ΔVOS = The allowable amount of overshoot voltage in load transition

    ΔVUS = The allowable amount of undershoot voltage in load transition

    Tmin(off) = Minimum off time

  3. Choose input capacitor.

    4. The TPS53128 requires an input decoupling capacitor and a bulk capacitor is needed depending on the application. A minimum 10-μF high-quality ceramic capacitor is recommended for the input capacitor. The capacitor voltage rating needs to be greater than the maximum input voltage.

  4. Choose bootstrap capacitor.

    5. The TPS53128 requires a bootstrap capacitor from SW to VBST to provide the floating supply for the high-side drivers. A minimum 0.1-μF high-quality ceramic capacitor is recommended. The voltage rating should be greater than 10 V.

  5. Choose VREG5 and V5FILT capacitor.

    6. The TPS53128 requires both the VREG5 regulator and V5FILT input are bypassed. A minimum 4.7-μF high-quality ceramic capacitor must be connected between the VREG5 and GND for proper operation. A minimum 1-μF high-quality ceramic capacitor must be connected between the V5FILT and GND for proper operation. Both of these capacitors’ voltage ratings should be greater than 10 V.

  6. Choose output voltage divider resistors.

    7. The output voltage is set with a resistor divider from the output voltage node to the VFBx pin. It is recommended to use 1% tolerance or better resisters. Select R2 between 10 kΩ and 100 kΩ and use Equation 12 or Equation 13 to calculate R1.

    Equation 12. TPS53128 eq_11z_lvs947.gif
    Equation 13. TPS53128 eq11a1_lvs947.gif

    Where

    VFB(RIPPLE) = Ripple voltage at VFB

    Vswinj = Ripple voltage at error comparator

  7. Choose register setting for over current limit.
    8. Equation 14. TPS53128 eq12a_lvs947.gif
    Equation 15. TPS53128 eq13a_lvs947.gif

    Where

    RDS(ON) = Low side FET on-resistance

    ITRIP(min) = TRIP pin source current （8.5 μA）

    VOCL0ff = Minimum over current limit offset voltage (–20 mV)

    IOCL = Over current limit

  8. Choose soft start capacitor.

    9. Soft start time equation is as follows.

    Equation 16. TPS53128 eq14_lvs947.gif

8.2.3 Application Curves

TPS53128 fsw18_lvsae4.gif
IO1 = 3 A VO1 = 1.8 V
Figure 12. Switching Frequency
vs
Input Voltage (Ch1)
TPS53128 fsw_18vio_lvsae4.gif
VO1 = 1.8 V
Figure 14. Switching Frequency
vs
Output Current (Ch1)
TPS53128 vo18vio_lvsae4.gif
VIN = 12 V VO1 = 1.8 V
Figure 16. Output Voltage
vs
Output Current (Ch1)
TPS53128 vovi18_lvsae4.gif
VIN = 12 V VO1 = 1.8 V
Figure 18. Output Voltage
vs
Input Voltage (Ch1)
TPS53128 load18_lvsae4.gif
Figure 20. Load Transient Response
TPS53128 start18_lvs947.gif
Figure 22. Start-Up Waveforms
TPS53128 effvio18_lvsae4.gif
VO1 = 1.8 V
Figure 24. 1.8-V Efficiency
vs
Output Current (Ch1)
TPS53128 vor18_lvsae4.gif
VO1 = 1.8 V
Figure 26. 1.8-V Output Ripple Voltage
TPS53128 fsw105_lvs947.gif
IO2 = 3 A VO2 = 1.05 V
Figure 13. Switching Frequency
vs
Input Voltage (Ch2)
TPS53128 fsw_105vio_lvsae4.gif
VO2 = 1.05 V
Figure 15. Switching Frequency
vs
Output Current (Ch2)
TPS53128 vo105vio_lvsae4.gif
VIN = 12 V VO2 = 1.05 V
Figure 17. Output Voltage
vs
Output Current (Ch2)
TPS53128 vovi105_lvsae4.gif
VIN = 12 V VO2 = 1.05 V
Figure 19. Output Voltage
vs
Input Voltage (Ch2)
TPS53128 load105_lvsae4.gif
Figure 21. Load Transient Response
TPS53128 start105_lvs947.gif
Figure 23. Start-Up Waveforms
TPS53128 effvio105_lvsae4.gif
VO2 = 1.05 V
Figure 25. 1.05-V Efficiency
vs
Output Current (Ch2)
TPS53128 vor105_lvsae4.gif
VO2 = 1.05 V
Figure 27. 1.05-V Output Ripple Voltage