JAJS521F December   2008  – May 2019 TPS61500

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      代表的なアプリケーション回路
  4. 4 改訂履歴
  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 Electrical Characteristics
    6. 6.6 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 Switching Frequency
      2. 7.3.2 Soft Start
      3. 7.3.3 Enable and Thermal Shutdown
      4. 7.3.4 Undervoltage Lockout (UVLO)
      5. 7.3.5 Overvoltage Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 PWM Dimming Method
      2. 7.4.2 Analog Dimming Method
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Analog Dimming Method
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Programming the Overvoltage Protection
          2. 8.2.1.2.2 Programming the LED Current
          3. 8.2.1.2.3 Implementing Dimming
          4. 8.2.1.2.4 Computing the Maximum Output Current
          5. 8.2.1.2.5 Selecting the Inductor
          6. 8.2.1.2.6 Selecting the Schottky Diode
          7. 8.2.1.2.7 Selecting the Compensation Capacitor and Resistor
          8. 8.2.1.2.8 Selecting the Input and Output Capacitor
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Pure PWM Dimming Method
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Considerations
  11. 11デバイスおよびドキュメントのサポート
    1. 11.1 デバイス・サポート
      1. 11.1.1 デベロッパー・ネットワークの製品に関する免責事項
      2. 11.1.2 ドキュメントの更新通知を受け取る方法
      3. 11.1.3 コミュニティ・リソース
    2. 11.2 商標
    3. 11.3 静電気放電に関する注意事項
    4. 11.4 Glossary
  12. 12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

8.2.1.2.4 Computing the Maximum Output Current

The overcurrent limit in a boost converter limits the maximum input current and thus maximum input power for a given input voltage. Maximum output power is less than maximum input power due to power conversion losses. Therefore, the current limit setting, input voltage, output voltage and efficiency can all change maximum current output. The current limit clamps the peak inductor current; therefore, the ripple has to be subtracted to derive maximum DC current. The ripple current is a function of switching frequency, inductor value and duty cycle. Equation 4 and Equation 5 take into account of all the above factors for maximum output current calculation.

Equation 4. TPS61500 eq_ip_lvs893.gif

where

  • Ip = inductor peak-to-peak ripple
  • L = inductor value
  • Vƒ = Schottky diode forward voltage
  • Fs = switching frequency
  • Vout = output voltage = Σ VLEDs + VREF
Equation 5. TPS61500 eq_iout_lvs893.gif

where

  • ILED_max = maximum LED current from the boost converter
  • Ilim = overcurrent limit
  • VLED = LED forward voltage at ILED
  • η = efficiency estimate based on similar applications

For instance, when VIN is 12 V, 8 LEDs output is equivalent to VOUT of 24 V, the inductor is 10 μH, the Schottky forward voltage is 0.4 V, and the switching frequency is 1.2 MHz; then the maximum output current is approximately 1 A in typical condition.