JAJSC97C January   2015  – September 2018 TPS7B7701-Q1 , TPS7B7702-Q1

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     アプリケーション図
  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 Switching Characteristics
    7. 6.7 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  Fault Detection and Protection
      2. 7.3.2  Short-Circuit and Overcurrent Protection
      3. 7.3.3  Short-to-Battery and Reverse Current Detection
      4. 7.3.4  Thermal Shutdown
      5. 7.3.5  Integrated Reverse-Polarity Protection
      6. 7.3.6  Integrated Inductive Clamp
      7. 7.3.7  Undervoltage Lockout
      8. 7.3.8  Enable (EN, EN1, and EN2)
      9. 7.3.9  Internal Voltage Regulator (VCC)
      10. 7.3.10 Current Sense Multiplexing
      11. 7.3.11 Adjustable Output Voltage (FB, FB1, and FB2)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation With IN < 4.5 V
      2. 7.4.2 Operation With EN Control
  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
        1. 8.2.2.1 Input Capacitor
        2. 8.2.2.2 Output Capacitor
        3. 8.2.2.3 Current Sense Resistor Selection
        4. 8.2.2.4 Current-Limit Resistor Selection
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11デバイスおよびドキュメントのサポート
    1. 11.1 ドキュメントのサポート
      1. 11.1.1 関連資料
    2. 11.2 関連リンク
    3. 11.3 ドキュメントの更新通知を受け取る方法
    4. 11.4 コミュニティ・リソース
    5. 11.5 商標
    6. 11.6 静電気放電に関する注意事項
    7. 11.7 Glossary
  12. 12メカニカル、パッケージ、および注文情報

8.2.2.4 Current-Limit Resistor Selection

The current at the LIMx pins (LIM, LIM1, and LIM2) is proportional to the load current at the OUTx (OUT, OUT1, and OUT2) pins and is internally connected to a current-limit comparator referenced to 1.233 V. The current limit is programmable through the external resistor connected at LIMx pin. Use Equation 5 to calculate the value of the external resistor, R(LIMx). The programmable current limit accuracy is 8% maximum across all conditions. The internal current limit of the device is set by shorting the LIM pin to ground. Because the current limit varies by 8%, Equation 6 shows how to calculate the minimum current limit value, and Equation 7 shows how to calculate the maximum current limit value.

Equation 5. TPS7B7701-Q1 TPS7B7702-Q1 tps7b77-rlim-equation.gif

where

  • TPS7B7701-Q1 TPS7B7702-Q1 tps7b77-ilim-typ-equation.gif
Equation 6. TPS7B7701-Q1 TPS7B7702-Q1 tps7b77-ilim-min-equation.gif
Equation 7. TPS7B7701-Q1 TPS7B7702-Q1 tps7b77-ilim-max-equation.gif

Select a maximum current-limit value of 200 mA and use Equation 8 to calculate the value of R(LIMx).

Equation 8. TPS7B7701-Q1 TPS7B7702-Q1 tps7b77-rlim-result-equation.gif

Using Equation 8 yields a RLIMx value of 1.318 kΩ. The closest 1% resistor that can be selected is 1.33 kΩ. Now using Equation 7 and plugging in 1.33 kΩ for RLIMx yields a maximum current of 198.2 mA. Keep in mind this result does not include resistor tolerance in the calculation. To make sure that the current does not exceed the set amount, resistor tolerance must also be included in the equation.