SNVSB66A July   2018  – October 2021 TPS3431


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Enable Input (EN) and Enable Output (ENOUT)
      2. 7.3.2 Watchdog Mode
        1. CWD
        2. Watchdog Input WDI
        3. Watchdog Output WDO
        4. SET1
    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 VDD(min) (VPOR ≤ VDD < VDD(min))
      3. 7.4.3 Normal Operation (VDD ≥ VDD(min))
  8. Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 CWD Functionality
        1. Factory-Programmed Timing Options
        2. CWD Adjustable Capacitor Watchdog Timeout
    2. 8.2 Typical Application
      1. 8.2.1 Design 1 Requirements
      2. 8.2.2 Detailed Design 1 Procedure
        1. Calculating WDO Pullup Resistor Design 1
        2. Setting the Watchdog Design 1
      3. 8.2.3 Application Curves Design 1
    3. 8.3 Programmable Application
      1. 8.3.1 Design 2 Requirements
      2. 8.3.2 Detailed Design 2 Procedure
        1. Calculating WDO Pullup Resistor Design 2
        2. Setting the Watchdog Design 2
        3. Watchdog Disabled During Initialization Period Design 2
        4. Programmable Disable Feature Design 2
      3. 8.3.3 Application Curves Design 2
  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

Pin Configuration and Functions

EN can also be left floating and is internally pulled-up to VDD
ENOUT can also be left floating or tied to WDO
Figure 5-1 DRB Package: TPS3431
3-mm × 3-mm VSON-8
Top View
Table 5-1 Pin Functions
VDD 1 I Supply voltage pin. For noisy systems, connecting a 0.1-μF bypass capacitor is recommended.
CWD 2 I Programmable watchdog timeout input. The watchdog timeout is set by connecting a capacitor between this pin and ground. Connecting via a 10-kΩ resistor to VDD or leaving unconnected further enables the selection of the preset watchdog timeouts; see the CWD Functionality section.
TheTPS3431 determines the watchdog timeout using Equation 1
EN 3 I Enable input pin. This pin is internally pulled up to VDD and must be logic high or left floating. When EN goes logic low, ENOUT goes logic low and WDI is ignored and WDO remains logic high. When EN goes logic high, ENOUT goes high (asserts) after the watchdog reset delay time (tRST). This pin can also be driven with an external push-button, transistor, or microcontroller.
GND 4 Ground pin
SET1 5 I Logic input. Grounding the SET1 pin disables the watchdog timer. SET1 and CWD select the watchdog timeouts; see the SET1 section.
WDI 6 I Watchdog input. A falling edge must occur at WDI before the timeout (tWD) expires.
When the watchdog is not in use, the SET1 pin can be used to disable the watchdog. WDI is ignored when WDO is low (asserted) and when the watchdog is disabled. If the watchdog is disabled, WDI cannot be left unconnected and must be driven to either VDD or GND.
WDO 7 O Watchdog open-drain active-low output. Connect WDO with a 1-kΩ to 100-kΩ resistor to the correct pull-up voltage rail (VPU). WDO goes low (asserts) when a watchdog timeout occurs. When a watchdog timeout occurs, WDO goes low (asserts) for the watchdog reset delay time (tRST). When EN goes low, WDO is in a high-impedance state and will be pulled to logic high.
ENOUT 8 O Enable open-drain active-high output. Connect ENOUT with a 1-kΩ to 100-kΩ resistor to the correct pull-up voltage rail (VPU). When EN goes logic high, ENOUT goes high impedance and pulls logic high (asserts) due to the external pull-up resistor after the watchdog reset delay time (tRST). When EN is forced logic low, ENOUT goes low after 200 ns and remains logic low as long as EN is logic low.
Thermal pad Connect the thermal pad to a large-area ground plane. The thermal pad is internally connected to GND.