SBVS286B March   2017  – July 2025 TPS3851-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Timing Requirements
    7. 5.7 Timing Diagrams
    8. 5.8 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 RESET
      2. 6.3.2 Manual Reset MR
      3. 6.3.3 UV Fault Detection
      4. 6.3.4 Watchdog Mode
        1. 6.3.4.1 CWD
        2. 6.3.4.2 Watchdog Input WDI
        3. 6.3.4.3 Watchdog Output WDO
        4. 6.3.4.4 SET1
    4. 6.4 Device Functional Modes
      1. 6.4.1 VDD is Below VPOR ( VDD < VPOR)
      2. 6.4.2 Above Power-On-Reset, But Less Than VDD(min) (VPOR ≤ VDD < VDD(min))
      3. 6.4.3 Normal Operation (VDD ≥ VDD(min))
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 CWD Functionality
        1. 7.1.1.1 Factory-Programmed Timing Options
        2. 7.1.1.2 Adjustable Capacitor Timing
      2. 7.1.2 Overdrive Voltage
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Monitoring the 1.8V Rail
        2. 7.2.2.2 Calculating the RESET and WDO Pullup Resistor
        3. 7.2.2.3 Setting the Watchdog
        4. 7.2.2.4 Watchdog Disabled During Initialization Period
      3. 7.2.3 Glitch Immunity
      4. 7.2.4 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Device Nomenclature
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.2.2.1 Monitoring the 1.8V Rail

The undervoltage comparator allows for precise voltage supervision of common rails between 1.8V and 5.0V. This application calls for very tight monitoring of the rail with only 5% of variation allowed on the rail. To make sure this requirement is met, the TPS3851G18S-Q1 is chosen for the –4% threshold. To calculate the worst-case for VITN, the accuracy must also be taken into account. The worst-case for VITN can be calculated by Equation 4:

Equation 4. VITN(Worst Case) = VITN(typ) × 0.992 = 1.8 × 0.96 × 0.992 = 1.714V