SBVS285 February   2017 TPS3852-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Circuit
      2.      Undervoltage Threshold (VITN) Accuracy vs Temperature
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 RESET
      2. 7.3.2 Manual Reset (MR)
      3. 7.3.3 Undervoltage Fault Detection
      4. 7.3.4 Watchdog Mode
        1. 7.3.4.1 SET1
        2. 7.3.4.2 Window Watchdog Timer
        3. 7.3.4.3 Watchdog Input (WDI)
        4. 7.3.4.4 CWD
        5. 7.3.4.5 Watchdog Output (WDO)
    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. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 CWD Functionality
        1. 8.1.1.1 Factory-Programmed Timing Options
        2. 8.1.1.2 Adjustable Capacitor Timing
      2. 8.1.2 Overdrive Voltage
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Monitoring the 3.3-V Rail
        2. 8.2.2.2 Calculating RESET and the WDO Pullup Resistor
        3. 8.2.2.3 Setting the Window Watchdog
        4. 8.2.2.4 Watchdog Disabled During Initialization Period
      3. 8.2.3 Glitch Immunity
      4. 8.2.4 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 Development Support
        1. 11.1.1.1 Evaluation Module
      2. 11.1.2 Device Nomenclature
    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

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • DRB|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.2.4 Watchdog Disabled During Initialization Period

The watchdog is often needed to be disabled during startup to allow for an initialization period. When the initialization period is over, the watchdog timer is turned back on to allow the microcontroller to be monitored by the TPS3852-Q1. To achieve this setup, SET1 must start at GND. In this design, SET1 is controlled by a TPS3890-Q1 supervisor. In this application, the TPS3890-Q1 was chosen to monitor VDD as well, meaning that RESET on the TPS3890-Q1 stays low until VDD rises above VITN. When VDD comes up, the delay time can be adjusted through the CT capacitor on the TPS3890-Q1. With this approach, the RESET delay can be adjusted from a minimum of 25 µs to a maximum of 30 seconds. For this design, a minimum delay of 7 seconds is needed until the watchdog timer is enabled. The CT capacitor calculation (see the TPS3890-Q1 data sheet) yields an ideal capacitance of 6.59 µF, giving a closest standard ceramic capacitor value of 6.8 µF. When connecting a 6.8-µF capacitor from CT to GND, the typical delay time is 7.21 seconds. Figure 22 illustrates the typical startup waveform for this circuit when the watchdog input is off. Figure 22 illustrates that when the watchdog is disabled, the WDO output remains high. See the TPS3890-Q1 data sheet for detailed information on the TPS3890-Q1.