SNVSCF5B June   2023  – March 2025 TPS35

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 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  Thermal Information
    6. 6.6  Electrical Characteristics
    7. 6.7  Timing Requirements
    8. 6.8  Switching Characteristics
    9. 6.9  Timing Diagrams
    10. 6.10 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 Voltage Supervisor
      2. 7.3.2 Timeout Watchdog Timer
        1. 7.3.2.1 tWD Timer
        2. 7.3.2.2 Watchdog Enable Disable Operation
        3. 7.3.2.3 tSD Watchdog Start Up Delay
        4. 7.3.2.4 SET Pin Behavior
      3. 7.3.3 Manual RESET
      4. 7.3.4 RESET and WDO Output
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Output Assert Delay
        1. 8.1.1.1 Factory-Programmed Output Assert Delay Timing
        2. 8.1.1.2 Adjustable Capacitor Timing
      2. 8.1.2 Watchdog Timer Functionality
        1. 8.1.2.1 Factory-Programmed Timing Options
        2. 8.1.2.2 Adjustable Capacitor Timing
    2. 8.2 Typical Applications
      1. 8.2.1 Design 1: Monitoring a Microcontroller Supply Voltage and Watchdog Timer
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Setting the Voltage Threshold
          2. 8.2.1.2.2 Meeting the Watchdog Timeout Period
          3. 8.2.1.2.3 Setting the Reset Delay
          4. 8.2.1.2.4 Setting the Startup Delay and Output Topology
          5. 8.2.1.2.5 Calculating the RESET Pullup Resistor
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.1.1.2 Adjustable Capacitor Timing

The TPS35 also utilizes a programmable output assert delay, using a precision current source to charge an external capacitor upon device startup. The typical delay time resulting from a given external capacitance on the CRST pin can be calculated by Equation 3, where tD is the output assert delay time in seconds and CCRST is the capacitance in microfarads.

Equation 3. tD (sec) = 4.95 × 106 × CCRST (F)

Note that to minimize the difference between the calculated output assert delay time and the actual output assert delay time, use a high-quality ceramic dielectric COG, X5R, or X7R capacitor and minimize parasitic board capacitance around this pin. Table 8-1 lists the output assert delay time for typical capacitor values.

Table 8-1 Output Assert Delay Time for Common Capacitor Values
CCRST

OUTPUT ASSERT

DELAY TIME (tD)		UNIT
MIN(1)TYPMAX(1)
10nF

39.6

49.5

59.4

ms
100nF

396

495

594

ms
1μF

3960

4950

5940

ms
(1) Minimum and maximum values are calculated using capacitor's typical value.