JAJSGR0F December   2010  – December 2018 TPS51916

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     アプリケーション概略
  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  VDDQ Switch Mode Power Supply Control
      2. 8.3.2  VREF and REFIN, VDDQ Output Voltage
      3. 8.3.3  Soft-Start and Powergood
      4. 8.3.4  Power State Control
      5. 8.3.5  Discharge Control
      6. 8.3.6  VTT and VTTREF
      7. 8.3.7  VDDQ Overvoltage and Undervoltage Protection
      8. 8.3.8  VDDQ Out-of-Bound Operation
      9. 8.3.9  VDDQ Overcurrent Protection
      10. 8.3.10 VTT Overcurrent Protection
      11. 8.3.11 V5IN Undervoltage Lockout Protection
      12. 8.3.12 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 MODE Pin Configuration
      2. 8.4.2 D-CAP™ Mode
    5. 8.5 D-CAP2™ Mode Operation
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 DDR3, D-CAP™ 400-kHz Application with Tracking Discharge
        1. 9.1.1.1 Design Requirements
        2. 9.1.1.2 Detailed Design Procedure
          1. 9.1.1.2.1 1. Determine the value of R1 AND R2
          2. 9.1.1.2.2 2. Choose the inductor
          3. 9.1.1.2.3 3. Choose the OCL setting resistance, RTRIP
          4. 9.1.1.2.4 Choose the output capacitors
        3. 9.1.1.3 Application Curves
      2. 9.1.2 DDR3, DCAP-2 500-kHz Application, with Tracking Discharge
        1. 9.1.2.1 Design Requirements
        2. 9.1.2.2 Detailed Design Procedure
          1. 9.1.2.2.1 Select Mode and Switching Frequency
          2. 9.1.2.2.2 Determine output capacitance
        3. 9.1.2.3 Application Curves
  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 ドキュメントの更新通知を受け取る方法
    2. 12.2 コミュニティ・リソース
    3. 12.3 商標
    4. 12.4 静電気放電に関する注意事項
    5. 12.5 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

8.3.9 VDDQ Overcurrent Protection

The VDDQ SMPS has cycle-by-cycle overcurrent limiting protection. The inductor current is monitored during the off-state using the low-side MOSFET RDS(on), and the controller maintains the off-state when the inductor current is larger than the overcurrent trip level. The current monitor circuit inputs are PGND and SW pins so that those should be properly connected to the source and drain terminals of low-side MOSFET. The overcurrent trip level, VOCTRIP, is determined by Equation 1, where RTRIP is the value of the resistor connected between the TRIP pin and GND, and ITRIP is the current sourced from the TRIP pin. ITRIP is 10 μA typically at room temperature, and has 4700ppm/°C temperature coefficient to compensate the temperature dependency of the low-side MOSFET RDS(on).

Equation 1. TPS51916 q_voctrip_lusae1.gif

Because the comparison is done during the off-state, VOCTRIP sets the valley level of the inductor current. The load current OCL level, IOCL, can be calculated by considering the inductor ripple current as shown in Equation 2.

Equation 2. TPS51916 q_iocl_lusae1.gif

where

  • IIND(ripple) is inductor ripple current

In an overcurrent condition, the current to the load exceeds the current to the output capacitor, thus the output voltage tends to fall down. Eventually, it crosses the undervoltage protection threshold and shuts down.