ZHCSMZ5D April   2020  – January 2023 TLV841

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 Device Comparison
  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 Timing Requirements
    7. 7.7 Timing Diagrams
    8. 7.8 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 Input Voltage (VDD)
        1. 8.3.1.1 VDD Hysteresis
        2. 8.3.1.2 VDD Transient Immunity
      2. 8.3.2 SENSE Input (TLV841S)
        1. 8.3.2.1 SENSE Hysteresis
        2. 8.3.2.2 Immunity to SENSE Pin Voltage Transients
      3. 8.3.3 User-Programmable Reset Time Delay for TLV841C only
      4. 8.3.4 Manual Reset (MR) Input for TLV841M only
      5. 8.3.5 Output Logic
        1. 8.3.5.1 RESET Output, Active-Low
        2. 8.3.5.2 RESET Output, Active-High
    4. 8.4 Device Functional Modes
      1. 8.4.1 Normal Operation (VDD > VPOR)
      2. 8.4.2 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
      3. 9.2.3 Application Curves: TLV841EVM
  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 Nomenclature
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 接收文档更新通知
    4. 12.4 支持资源
    5. 12.5 Trademarks
    6. 12.6 静电放电警告
    7. 12.7 术语表
  13. 13Mechanical, Packaging, and Orderable Information

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8.3.3 User-Programmable Reset Time Delay for TLV841C only

The reset time delay can be set to a typical value of 40 µs by leaving the CT pin floating, or a maximum value of approximately 6.2 seconds by connecting 10 µF delay capacitor. The reset time delay (tD) can be programmed by connecting a capacitor no larger than 10 µF between the CT pin and GND.

The relationship between external capacitor (CCT_EXT (typ)) in µF at CT pin and the time delay (tD (typ)) in seconds is given by #SNVSBC358016.

Equation 3. tD (typ) = -ln (0.29) x RCT (typ) x CCT_EXT (typ) + tD (no cap, typ)

#SNVSBC358016 is simplified to #T5037184-33 by plugging RCT (typ) and tD (no cap, typ) given in GUID-XXXXXXXX-SF0T-XXXX-XXXX-000000182866.html#GUID-XXXXXXXX-SF0T-XXXX-XXXX-000000182866 and GUID-XXXXXXXX-SF0T-XXXX-XXXX-000000182867.html#GUID-XXXXXXXX-SF0T-XXXX-XXXX-000000182867:

Equation 4. tD (typ) = 618937 x CCT_EXT (typ) + 40 µs

#T5037184-34 solves for external capacitor value CCT_EXT in units of µF where tD (typ) is in units of seconds

Equation 5. CCT_EXT = (tD (typ) - 40 µs) ÷ 618937
The reset delay varies according to three variables: the external capacitor CCT_EXT, CT pin internal resistance RCT provided in GUID-XXXXXXXX-SF0T-XXXX-XXXX-000000182866.html#GUID-XXXXXXXX-SF0T-XXXX-XXXX-000000182866, and a constant. The maximum variance due to the constant is show in #GUID-687B2601-AB90-4DEF-AB08-06772E81FF72:
Equation 6. tD (max) = -ln (0.25) x RCT (max) x CCT_EXT (max) + tD (no cap, max)

The recommended maximum delay capacitor for the TLV841C is limited to 10 μF as this ensures enough time for the capacitor to fully discharge when a voltage fault occurs. Also, having a too large of a capacitor value can cause very slow charge up (rise times) and system noise can cause the the internal circuit to trip earlier or later near the threshold. This leads to variation in time delay where it can make the delay accuracy worse in the presence of system noise.

When a voltage fault occurs, the previously charged up capacitor discharges and if the monitored voltage returns from the fault condition before the delay capacitor discharges completely, the delay will be shorter than expected. The capacitor will begin charging from a voltage above zero and resulting in shorter than expected time delay. A larger delay capacitor can be used so long as the capacitor has enough time to fully discharge during the duration of the voltage fault. The amount of time required to discharge the delay capacitor relative to the reset delay rises as VDD fault undervoltage increases as shown in #T5753602-4. From the graph below, to ensure the CCT_EXT capacitor is fully discharged, the time period or duration of the voltage fault needs to be greater than 10% of the programmed reset time delay.

GUID-6728E1AD-FFE7-4471-B00F-57721FA127B6-low.gif Figure 8-5 CCT_EXT Discharge Time During Fault Condition (CCT_EXT = 1 µF)