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

8.2.2.3 Setting the Window Watchdog

As illustrated in Figure 18, there are three options for setting the window watchdog. The design specifications in this application require the programmable timing option (external capacitor connected to CWD). When a capacitor is connected to the CWD pin, the window is governed by Equation 4. Equation 4 is only valid for ideal capacitors, any temperature or voltage derating must be accounted for separately.

Equation 4. TPS3852-Q1 q_ccwd_sbvs301.gif

The nearest standard capacitor value to 2.5 nF is 2.2 nF. Selecting 2.2 nF for the CCWD capacitor gives the following minimum and maximum timing parameters:

Equation 5. TPS3852-Q1 q_twdumin_sbvs301.gif
Equation 6. TPS3852-Q1 q_twdlmax_sbvs301.gif

Capacitor tolerance also influence tWDU(MIN) and tWDL(MAX). Select a ceramic COG dielectric capacitor for high accuracy. For 2.2 nF, COG capacitors are readily available with a 5% tolerance, which results in a 5% decrease in tWDU(MIN) and a 5% increase in tWDL(MAX), giving 181 ms and 135 ms, respectively. A falling edge must be issued within this window.