SLVSGE8B November   2022  – August 2024 TPS35-Q1

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 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Timing Diagrams
    9. 6.9 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 CRST Delay
        1. 8.1.1.1 Factory-Programmed watchdog Timing
        2. 8.1.1.2 Adjustable Capacitor Timing
      2. 8.1.2 Watchdog Timer Functionality
        1. 8.1.2.1 Factory-Programmed watchdog Timing
        2. 8.1.2.2 Adjustable Capacitor Timings
    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. 8.2.1.3 Application Curves
    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

Package Options

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

7.3.2.4 SET Pin Behavior

The TPS35-Q1 offers one or two SET pins based on the pinout option selected. SET pins offer flexibility to the user to program the tWD timer on the fly to meet various application requirements. Typical use cases where SET pin can be used are:

  • Use wide timeout timer when host is in sleep mode, change to small timeout operation when host is operational. Watchdog can be used to wake up the host after long duration to perform the application related activities before going back to sleep.
  • Change to wide timeout timer when performing system critical tasks to make sure the watchdog does not interrupt the critical task. Change timer to application specified interval after the critical task is complete.

The tWD timer value for the device is combination of timer selection based on the CWD pin or fixed timer value along with SET pin logic level. The base tWD timer value is decided based on the Watchdog Time selector in the Section 4 section. The SET pin logic level is decoded during the device power up. The SET pin value can be changed any time during the operation. SETx pin change which leads to change of watchdog timer value or enable disable state, terminates the ongoing watchdog frame immediately. SETx pins can be updated when WDO or RESET output is asserted as well. The updated tWD timer value is going be applied after output is deasserted and the tSD timer is over or terminated.

For a pinout which offers only SET0 pin to the user, the tWD multiplier value is decided based on the Watchdog Time Scaling selector in the Section 4 section. Table 7-1 showcases an example of the tWD values for different SET0 logic levels when using Watchdog Time setting as option D = 10ms.

Table 7-1 tWD Scaling with SET0 Pin Only (Pin Configuration A)
WATCHDOG TIME SCALING SELECTIONtWD
SET0 = 0SET0 = 1
A10ms20ms
B10ms40ms
C10ms80ms
D10ms160ms
E10ms320ms
F10ms640ms
G10ms1280ms

For pinouts which offer both SET0 & SET1 pins to the user, the tWD multiplier value is decided based on the Watchdog Time Scaling selector in the Section 4 section. Two SETx pins offer 3 different time scaling options. The SET[1:0] = 0b'01 combination disables the watchdog operation. Table 7-2 showcases an example of the tWD values for different SET[1:0] logic levels when using Watchdog Time setting as option G = 100ms. The package pin out selected does not offer WD-EN pin.

Table 7-2 tWD Scaling with SET0 & SET1 Pins, WD-EN Pin Not Available (Pin Configuration B)
WATCHDOG TIME SCALING SELECTIONtWD
SET[1:0] = 0b'00SET[1:0] = 0b'01SET[1:0] = 0b'10SET[1:0] = 0b'11
A100msWatchdog disable200ms400ms
B100msWatchdog disable400ms800ms
C100msWatchdog disable800ms1600ms
D100msWatchdog disable1600ms3200ms
E100msWatchdog disable3200ms6400ms
F100msWatchdog disable6400ms12800ms
G100msWatchdog disable12800ms25600ms

Selected pinout option can offer WD-EN pin along with SET[1:0] pins (Pin Configuration C, D). With this pinout, the WD-EN pin controls watchdog enable and disable operation. The SET[1:0] = 0b'01 combination operates as SET[1:0] = 0b'00.

Make sure the tWD value with SETx multiplier does not exceed 640s. If a selection of timer and multiplier results in tWD > 640s, the timer value is restricted to 640s.

Figure 7-9 to Figure 7-11 diagrams show the timing behavior with respect to SETx status changes.

TPS35-Q1 Watchdog Behavior with SETx Pin StatusFigure 7-9 Watchdog Behavior with SETx Pin Status
TPS35-Q1 Watchdog Operation with 2 SET PinsFigure 7-10 Watchdog Operation with 2 SET Pins
TPS35-Q1 Watchdog Operation with 1 SET PinFigure 7-11 Watchdog Operation with 1 SET Pin