ZHCSM34M May   2004  – March 2023 TPS3808

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 Device Voltage Thresholds
  6. 6 Pin Configuration and 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 Switching Characteristics
    7. 7.7 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 SENSE Input
      2. 8.3.2 Selecting the RESET Delay Time
      3. 8.3.3 Manual RESET ( MR) Input
      4. 8.3.4 RESET Output
    4. 8.4 Device Functional Modes
      1. 8.4.1 Normal Operation (VDD > VDD(min))
      2. 8.4.2 Above Power-On Reset but Less Than VDD(min) (VPOR < VDD < VDD(min))
      3. 8.4.3 Below Power-On Reset (VDD < VPOR)
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Immunity to SENSE Pin Voltage Transients
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
        1. 12.1.1.1 Evaluation Modules
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 支持资源
    4. 12.4 Trademarks
    5. 12.5 静电放电警告
    6. 12.6 术语表
  13. 13Mechanical, Packaging, and Orderable Information

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8.3.2 Selecting the RESET Delay Time

The TPS3808 has three options for setting the RESET delay time as shown in Figure 8-2. Figure 8-2 (a) shows the configuration for a fixed 300-ms typical delay time by tying CT to VDD; a resistor from 40 kΩ to 200 kΩ must be used. Supply current is not affected by the choice of resistor. Figure 8-2 (b) shows a fixed 20-ms delay time by leaving the CT pin open. Figure 8-2 (c) shows a ground referenced capacitor connected to CT for a user-defined program time between 1.25 ms and 10 s.

GUID-E2367CF4-1E1C-4674-8B7A-E1DC68F0D664-low.gifFigure 8-2 Configuration Used to Set the RESET Delay Time

The capacitor CT should be ≥ 100 pF nominal value in order for the TPS3808xxx to recognize that the capacitor is present. The capacitor value for a given delay time can be calculated using Equation 1.

Equation 1. GUID-5F0F071D-4EA1-40B1-85D3-BEE8CB832E42-low.gif

The reset delay time is determined by the time it takes an on-chip precision 220-nA current source to charge the external capacitor to 1.23 V. When a RESET is asserted, the capacitor is discharged. When the RESET conditions are cleared, the internal current source is enabled and begins to charge the external capacitor. When the voltage on this capacitor reaches 1.23 V, RESET is deasserted. Note that a low-leakage type capacitor such as a ceramic should be used, and that stray capacitance around this pin may cause errors in the reset delay time.