SNVSC27B October   2022  – January 2025 TPS38700

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 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Device State Diagram
      2. 7.3.2 Built-In Self Test and Configuration Load
      3. 7.3.3 CLK32K
      4. 7.3.4 BACKUP State
      5. 7.3.5 FAILSAFE State
      6. 7.3.6 Transitioning Sequences
        1. 7.3.6.1 Sequence 1: Power Up
        2. 7.3.6.2 Sequence 2: Emergency Power Down
        3. 7.3.6.3 Sequence 3: Sleep Entry
        4. 7.3.6.4 Sequence 4: Sleep Exit
        5. 7.3.6.5 Sequence 5 & 6: Power Down from Active and Sleep States
        6. 7.3.6.6 Sequence 7: Sleep Exit Due to NRST_IN
        7. 7.3.6.7 Sequence 8: RESET Due to NRST_IN
        8. 7.3.6.8 Sequence 9: Failsafe Power Down
        9. 7.3.6.9 Output Sequencing
      7. 7.3.7 I2C
        1. 7.3.7.1 Packet Error Checking (PEC)
    4. 7.4 Register Map Table
      1. 7.4.1 Register Descriptions
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Automotive Multichannel Sequencer and Monitor
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
      4. 8.2.4 Application Curves
    3. 8.3 Power Supply Recommendations
      1. 8.3.1 Power Supply Guidelines
    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 Device Nomenclature
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12.   Mechanical, Packaging, and Orderable Information

7.3.3 CLK32K

The TPS38700 is designed to give an accurate CLK32K output and it is used internally for setting the RTC time and alarms. TPS38700 is configured to be used with a 32.768kHz crystal oscillator. To achieve a well-defined frequency of oscillations, all crystals oscillators are tuned at specific capacitive load such as 6.5pF, 12pF, or
20pF (during manufacturing stage), which becomes a part of the crystal specification. The task of a designer is to design within the crystal's specifications to achieve the correct specified frequency.

For these crystal oscillators, the need for loading capacitors are required because the capacitive load is effectively split between the output and input capacitance in a typical Pierce Oscillator scheme. These capacitors are essentially connected in series with the crystal oscillator. Therefore, if a chosen crystal oscillator has a capacitive load that is specified for 12.5pF load, then the need for two 12.5pF capacitors are required for proper frequency output from the crystal oscillator.

The TPS38700 is configured to be used without the need of loading capacitors, as long as the 6.5pF version of the external crystal oscillator is selected. External crystal oscillators will typically specify their internal capacitance such as 6.5pF, 9pF, 12.5pF etc. If the external crystal oscillator has load capacitance specification requirement not equal to 6.5pF, please contact the TI factory for an OTP (one time programming) configuration for the correct external capacitor loading.

The CLK32K signal can start as late as 50ms from when the input voltage VDD exits out of UVLO. The accuracy of CLK32K is within ±100ppm after one second of initial operation. If the frequency of CLK32K deviates for more than ±10%, a fault interrupt is asserted. The accuracy of the CLK32K will also depend on the choice of external crystal oscillator and its temperature rating.