SLVSD43C May   2015  – February 2019 TPS7B68-Q1


  1. Features
  2. Applications
  3. Description
    1.     Typical Application Schematic
  4. Revision History
  5. Pin Configuration and Functions
    1.     Pin 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 Switching Characteristics
    7. 6.7 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Device Enable (EN)
      2. 7.3.2 Adjustable Power-Good Threshold (PG, PGADJ)
      3. 7.3.3 Adjustable Power-Good Delay Timer (DELAY)
      4. 7.3.4 Undervoltage Shutdown
      5. 7.3.5 Current Limit
      6. 7.3.6 Thermal Shutdown
      7. 7.3.7 Integrated Watchdog
        1. Window Watchdog (WTS, ROSC, FSEL and WRS)
        2. Standard Watchdog (WTS, ROSC and FSEL)
        3. Watchdog Service Signal and Watchdog Fault Outputs (WD and WDO)
        4. ROSC Status Detection (ROSC)
        5. Watchdog Enable (PG and WD_EN)
        6. Watchdog Initialization
        7. Window Watchdog Operation (WTS = Low)
        8. Standard Watchdog Operation (WTS = High)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation With Input Voltage Lower Than 4 V
      2. 7.4.2 Operation With Input Voltage Higher Than 4 V
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. Input Capacitor
        2. Output Capacitor
        3. Power-Good Threshold
        4. Power-Good Delay Period
        5. Watchdog Setup
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

Window Watchdog Operation (WTS = Low)

The window watchdog is able to monitor whether the frequency of the watchdog service signal (WD) is within certain ranges. A watchdog low-voltage fault is reported when the frequency of the watchdog service signal is out of the setting range. Figure 24 shows the window watchdog initialization and operation for the TPS7B68-Q1 (WRS is low). After the output voltage is in regulation and PG is high, the window watchdog becomes enabled when an external signal pulls WD_EN (the watchdog enable pin) low. This causes the watchdog to initialize and wait for a service signal during the first initialization window for 8 times the duration of t(WD). A service signal applied to the WD pin during the initialization open window resets the watchdog counter and a closed window starts. To prevent a fault condition from occurring, watchdog service must not occur during the closed window. Watchdog service must occur during the following open window to prevent a fault condition from occurring. The fault output (WDO), externally pulled up to VOUT (typical), stays high as long as the watchdog receives a proper service signal and there is no other fault condition.

TPS7B68-Q1 wind-wd-oper_SLVSD43.gif


V(PG_TH) rising = V(PG_TH) falling + V(PG_HYST).
Figure 24. Window Watchdog Operation

Three different fault conditions occur in Figure 24:

  • Fault 1: The watchdog service signal is received during the closed window. The WDO is triggered one time, receiving a WD rising edge during the closed window.
  • Fault 2: The watchdog service signal is not received during the open window. WDO is triggered after the maximum open-window duration t(WD) / 2.
  • Fault 3: The watchdog service signal is not received during the WD initialization. WDO is triggered after the maximum initialization window duration 8 × t(WD).