SBVS301B October   2016  – September 2021 TPS3850

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Timing Diagrams
    8. 6.8 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 CRST
      2. 7.3.2 RESET
      3. 7.3.3 Over- and Undervoltage Fault Detection
      4. 7.3.4 Adjustable Operation Using the TPS3850H01
      5. 7.3.5 Window Watchdog
        1. 7.3.5.1 SET0 and SET1
          1. 7.3.5.1.1 Enabling the Window Watchdog
          2. 7.3.5.1.2 Disabling the Watchdog Timer When Using the CRST Capacitor
          3. 7.3.5.1.3 SET0 and SET1 During Normal Watchdog Operation
      6. 7.3.6 Window Watchdog Timer
        1. 7.3.6.1 CWD
        2. 7.3.6.2 WDI Functionality
        3. 7.3.6.3 WDO Functionality
    4. 7.4 Device Functional Modes
      1. 7.4.1 VDD is Below VPOR ( VDD < VPOR)
      2. 7.4.2 Above Power-On-Reset But Less Than UVLO (VPOR ≤ VDD < VUVLO)
      3. 7.4.3 Above UVLO But Less Than VDD (min) (VUVLO ≤ VDD < VDD (min))
      4. 7.4.4 Normal Operation (VDD ≥ VDD (min))
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 CRST Delay
        1. 8.1.1.1 Factory-Programmed Reset Delay Timing
        2. 8.1.1.2 Programmable Reset Delay-Timing
      2. 8.1.2 CWD Functionality
        1. 8.1.2.1 Factory-Programmed Timing Options
        2. 8.1.2.2 Adjustable Capacitor Timing
      3. 8.1.3 Adjustable SENSE Configuration
      4. 8.1.4 Overdrive on the SENSE Pin
    2. 8.2 Typical Applications
      1. 8.2.1 Design 1: Monitoring a 1.2-V Rail with Factory-Programmable Watchdog Timing
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Monitoring the 1.2-V Rail
          2. 8.2.1.2.2 Meeting the Minimum Reset Delay
          3. 8.2.1.2.3 Setting the Watchdog Window
          4. 8.2.1.2.4 Calculating the RESET and WDO Pullup Resistor
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Design 2: Using TPS3850H01 to monitor a 0.7-V Rail With an Adjustable Window Watchdog Timing
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Meeting the Minimum Reset Delay
          2. 8.2.2.2.2 Setting the Window Watchdog
          3. 8.2.2.2.3 Watchdog Disabled During the Initialization Period
          4. 8.2.2.2.4 Calculating the Sense Resistor
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Device Nomenclature
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.6.2 WDI Functionality

WDI is the watchdog timer input that controls the WDO output. The WDI input is triggered by the falling edge of the input signal. For the first pulse, the watchdog acts as a traditional watchdog timer; thus, the first pulse must be issued before tWDU(min). After the first pulse, to ensure proper functionality of the watchdog timer, always issue the WDI pulse within the window of tWDL(max) and tWDU(min). If the pulse is issued in this region, then WDO remains unasserted. Otherwise, the device asserts WDO, putting the WDO pin into a low-impedance state.

The watchdog input (WDI) is a digital pin. To ensure there is no increase in IDD, drive the WDI pin to either VDD or GND at all times. Putting the pin to an intermediate voltage can cause an increase in supply current (IDD) because of the architecture of the digital logic gates. When RESET is asserted, the watchdog is disabled and all signals input to WDI are ignored. When RESET is no longer asserted, the device resumes normal operation and no longer ignores the signal on WDI. If the watchdog is disabled, drive the WDI pin to either VDD or GND.