SBVS366A July   2018  – October 2021 TPS3430

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 Window Watchdog
        1. 7.3.2.1 SET0 and SET1
          1. 7.3.2.1.1 Enabling the Window Watchdog
          2. 7.3.2.1.2 Disabling the Watchdog Timer When Using the CRST Capacitor
          3. 7.3.2.1.3 SET0 and SET1 During Normal Watchdog Operation
      3. 7.3.3 Window Watchdog Timer
        1. 7.3.3.1 CWD
        2. 7.3.3.2 WDI Functionality
        3. 7.3.3.3 WDO Functionality
    4. 7.4 Device Functional Modes
      1. 7.4.1 VDD is Below VPOR ( VDD < VPOR)
      2. 7.4.2 VDD is Above VPOR And Below VDD (min)( VPOR < VDD < VDD (min))
      3. 7.4.3 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 Watchdog Reset Delay Timing
        2. 8.1.1.2 CRST Programmable Watchdog Reset Delay
      2. 8.1.2 CWD Functionality
        1. 8.1.2.1 Factory-Programmed Timing Options
        2. 8.1.2.2 CWD Adjustable Capacitor Watchdog Timeout
    2. 8.2 Typical Applications
      1. 8.2.1 Monitoring Microcontroller with Watchdog Timer - Design 1
        1. 8.2.1.1 Design Requirements - Design 1
        2. 8.2.1.2 Detailed Design Procedure - Design 1
          1. 8.2.1.2.1 Meeting the Minimum Watchdog Reset Delay - Design 1
          2. 8.2.1.2.2 Setting the Watchdog Window - Design 1
          3. 8.2.1.2.3 Calculating the WDO Pull-up Resistor - Design 1
      2. 8.2.2 Monitoring Microcontroller with a Programmed Window Watchdog Timer - Design 2
        1. 8.2.2.1 Design Requirements - Design 2
        2. 8.2.2.2 Detailed Design Procedure - Design 2
          1. 8.2.2.2.1 Meeting the Minimum Watchdog Reset Delay - Design 2
          2. 8.2.2.2.2 Setting the Watchdog Window - Design 2
          3. 8.2.2.2.3 Calculating the WDO Pull-up Resistor - Design 2
      3. 8.2.3 Monitoring Microcontroller with a Latching Window Watchdog Timer - Design 3
        1. 8.2.3.1 Design Requirements - Design 3
        2. 8.2.3.2 Detailed Design Procedure - Design 3
          1. 8.2.3.2.1 Meeting the Latching Output Requirement - Design 3
          2. 8.2.3.2.2 Setting the Watchdog Window - Design 3
        3. 8.2.3.3 Application Curve - Design 3
  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
    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

8.1.1.2 CRST Programmable Watchdog Reset Delay

The TPS3430 uses a CRST pin charging current (ICRST) of 375 nA. When using an external capacitor, the rising WDO delay time can be set to any value between 700 µs (CCRST = 100 pF) and 3.2 seconds (CCRST = 1 µF). The typical ideal capacitor value needed for a given delay time can be calculated using Equation 1, where CCRST is in microfarads and tRST is in seconds:

Equation 1. tRST = 3.22 × CCRST + 0.000381

To calculate the minimum and maximum watchdog reset delay time use Equation 2 and Equation 3, respectively.

Equation 2. tRST(min) = 2.8862 × CCRST + 0.000324
Equation 3. tRST(max) = 3.64392 × CCRST + 0.000438

The slope of Equation 1 is determined by the time the CRST charging current (ICRST) takes to charge the external capacitor up to the CRST comparator threshold voltage (VCRST). When WDO is asserted, the capacitor is discharged through the internal CRST pulldown resistor. When the WDO conditions are cleared, the internal precision current source is enabled and begins to charge the external capacitor; when VCRST = 1.21 V, WDO is unasserted. Note to minimize the difference between the calculated WDO delay time and the actual WDO delay time, use a use a high-quality ceramic dielectric COG, X5R, or X7R capacitor and minimize parasitic board capacitance around this pin. Table 8-2 lists the watchdog reset delay time ideal capacitor values for CCRST.

Table 8-2 Watchdog Reset Delay Time for Common Ideal Capacitor Values
CCRSTWDO DELAY TIME (tRST)UNIT
MIN(1)TYPMAX(1)
100 pF0.610.700.80ms
1 nF3.213.614.08ms
10 nF29.232.636.8ms
100 nF289323364ms
1 μF288632273644ms
(1) Minimum and maximum values are calculated using ideal capacitors.