JAJS448D March   2010  – October 2018 TPS54260

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      概略回路図
      2.      効率と負荷電流との関係
  4. 4 改訂履歴
  5. 5 概要（続き）
  6. 6 Pin Configuration and Functions
    1.     Pin 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 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Fixed Frequency PWM Control
      2. 8.3.2  Slope Compensation Output Current
      3. 8.3.3  Pulse-Skip Eco-Mode
      4. 8.3.4  Low-Dropout Operation and Bootstrap Voltage (BOOT)
      5. 8.3.5  Error Amplifier
      6. 8.3.6  Voltage Reference
      7. 8.3.7  Adjusting the Output Voltage
      8. 8.3.8  Enable and Adjusting Undervoltage Lockout
      9. 8.3.9  Slow-Start / Tracking Pin (SS/TR)
      10. 8.3.10 Overload Recovery Circuit
      11. 8.3.11 Sequencing
      12. 8.3.12 Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
      13. 8.3.13 Overcurrent Protection and Frequency Shift
      14. 8.3.14 Selecting the Switching Frequency
      15. 8.3.15 How to Interface to RT/CLK Pin
      16. 8.3.16 Powergood (PWRGD Pin)
      17. 8.3.17 Overvoltage Transient Protection
      18. 8.3.18 Thermal Shutdown
      19. 8.3.19 Small Signal Model for Loop Response
      20. 8.3.20 Simple Small Signal Model for Peak Current Mode Control
      21. 8.3.21 Small Signal Model for Frequency Compensation
    4. 8.4 Device Functional Modes
      1. 8.4.1 Operation Near Minimum Input Voltage
      2. 8.4.2 Operation With Enable Control
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 3.3-V Output Application
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1  Custom Design With WEBENCH® Tools
          2. 9.2.1.2.2  Selecting the Switching Frequency
          3. 9.2.1.2.3  Output Inductor Selection (LO)
          4. 9.2.1.2.4  Output Capacitor
          5. 9.2.1.2.5  Catch Diode
          6. 9.2.1.2.6  Input Capacitor
          7. 9.2.1.2.7  Slow-Start Capacitor
          8. 9.2.1.2.8  Bootstrap Capacitor Selection
          9. 9.2.1.2.9  Undervoltage Lock Out Set Point
          10. 9.2.1.2.10 Output Voltage and Feedback Resistors Selection
          11. 9.2.1.2.11 Compensation
          12. 9.2.1.2.12 Discontinuous Mode and Eco-Mode Boundary
          13. 9.2.1.2.13 Power Dissipation Estimate
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Inverting Power Supply
      3. 9.2.3 Split-Rail Power Supply
      4. 9.2.4 12-V to 3.8-V GSM Power Supply
      5. 9.2.5 24-V to 4.2-V GSM Power Supply
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12デバイスおよびドキュメントのサポート
    1. 12.1 デバイス・サポート
      1. 12.1.1 デベロッパー・ネットワークの製品に関する免責事項
      2. 12.1.2 開発サポート
        1. 12.1.2.1 WEBENCH®ツールによるカスタム設計
    2. 12.2 ドキュメントの更新通知を受け取る方法
    3. 12.3 コミュニティ・リソース
    4. 12.4 商標
    5. 12.5 静電気放電に関する注意事項
    6. 12.6 Glossary
  13. 13メカニカル、パッケージ、および注文情報

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
発注情報

8.3.20 Simple Small Signal Model for Peak Current Mode Control

Figure 47 describes a simple small signal model that can be used to understand how to design the frequency compensation. The TPS54260 power stage can be approximated to a voltage-controlled current source (duty cycle modulator) supplying current to the output capacitor and load resistor. The control to output transfer function is shown in Equation 14 and consists of a DC gain, one dominant pole, and one ESR zero. The quotient of the change in switch current and the change in COMP pin voltage (node C in Figure 46) is the power stage transconductance. The gmPS for the TPS54260 is 10.5 S. The low-frequency gain of the power stage frequency response is the product of the transconductance and the load resistance as shown in Equation 15.

As the load current increases and decreases, the low-frequency gain decreases and increases, respectively. This variation with the load may seem problematic at first glance, but fortunately the dominant pole moves with the load current (see Equation 16). The combined effect is highlighted by the dashed line in the right half of Figure 47. As the load current decreases, the gain increases and the pole frequency lowers, keeping the 0-dB crossover frequency the same for the varying load conditions which makes it easier to design the frequency compensation. The type of output capacitor chosen determines whether the ESR zero has a profound effect on the frequency compensation design. Using high-ESR aluminum electrolytic capacitors may reduce the number frequency compensation components needed to stabilize the overall loop because the phase margin increases from the ESR zero at the lower frequencies (see Equation 17).

TPS54260 peak_cur_lvs795.gifFigure 47. Simple Small Signal Model and Frequency Response for Peak Current Mode Control
Equation 14. TPS54260 q_voovervc_lvs795.gif
Equation 15. TPS54260 eq15_lvs795.gif
Equation 16. TPS54260 q_fp_lvs795.gif
Equation 17. TPS54260 q_fz_lvs795.gif