JAJSGL5C December   2018  – August 2019 TPS3840

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
      2.      TPS3840 の標準的な消費電流
  4. 4 改訂履歴
  5. 5 概要 (続き)
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
    1.     Pin Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Timing Requirements
    7. 8.7 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Input Voltage (VDD)
        1. 9.3.1.1 VDD Hysteresis
        2. 9.3.1.2 VDD Transient Immunity
      2. 9.3.2 User-Programmable Reset Time Delay
      3. 9.3.3 Manual Reset (MR) Input
      4. 9.3.4 Output Logic
        1. 9.3.4.1 RESET Output, Active-Low
        2. 9.3.4.2 RESET Output, Active-High
    4. 9.4 Device Functional Modes
      1. 9.4.1 Normal Operation (VDD > VDD(min))
      2. 9.4.2 VDD Between VPOR and VDD(min)
      3. 9.4.3 Below Power-On-Reset (VDD < VPOR)
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design 1: Dual Rail Monitoring with Power-Up Sequencing
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
        3. 10.2.1.3 Application Curves
      2. 10.2.2 Design 2: Battery Voltage and Temperature Monitor
        1. 10.2.2.1 Design Requirements
        2. 10.2.2.2 Detailed Design Procedure
      3. 10.2.3 Design 3: Fast Start Undervoltage Supervisor with Level-shifted Input
        1. 10.2.3.1 Design Requirements
        2. 10.2.3.2 Detailed Design Procedure
      4. 10.2.4 Design 4: Voltage Monitor with Back-up Battery Switchover
        1. 10.2.4.1 Design Requirements
        2. 10.2.4.2 Detailed Design Procedure
      5. 10.2.5 Application Curve: TPS3840EVM
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13デバイスおよびドキュメントのサポート
    1. 13.1 デバイスの項目表記
    2. 13.2 コミュニティ・リソース
    3. 13.3 商標
    4. 13.4 静電気放電に関する注意事項
    5. 13.5 Glossary
  14. 14メカニカル、パッケージ、および注文情報

10.2.1.2 Detailed Design Procedure

The primary constraint for this application is choosing the correct device to monitor the supply voltage of the microprocessor. The TPS3840 can monitor any voltage between 1.6 V and 10 V and is available in 0.1 V increments. Depending on how far away from the nominal voltage rail the user wants the voltage supervisor to trigger determines the correct voltage supervisor variant to choose. In this example, the first TPS3840 triggers when the 3.3-V rail falls to 3.0 V. The second TPS3840 triggers a reset when the 1.8-V rail falls to 1.6 V. The secondary constraint for this application is the reset time delay that must be at least 25 ms to allow the microprocessor, and all other devices using the 3.3-V rail, enough time to startup correctly before the 1.8-V rail is enabled via the LDO. Because a minimum time is required, the user must account for capacitor tolerance. For applications with ambient temperatures ranging from –40°C to +125°C, CCT can be calculated using RCT and solving for CCT in Equation 2. Solving Equation 2 for 25 ms gives a minimum capacitor value of 0.04 µF which is rounded up to a standard value 0.047 µF to account for capacitor tolerance.

A 1-µF decoupling capacitor is connected to the VDD pin as a good analog design practice. The pull-up resistor is only required for the Open-Drain device variants and is calculated to maintain the RESET current within the ±5 mA limit found in the Recommended Operating Conditions: RPull-up = VPull-up ÷ 5 mA. For this design, a standard 10-kΩ pull-up resistor is selected to minimize current draw when RESET is asserted. Keep in mind the lower the pull-up resistor, the higher VOL. The MR pin can be connected to an external signal if desired or left floating if not used due to the internal pull-up resistor to VDD.