SCPS260C August   2017  – February 2022 TIC12400-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  VS Pin
      2. 8.3.2  VDD Pin
      3. 8.3.3  Device Initialization
      4. 8.3.4  Device Trigger
      5. 8.3.5  Device Reset
        1. 8.3.5.1 VS Supply POR
        2. 8.3.5.2 Hardware Reset
        3. 8.3.5.3 Software Reset
      6. 8.3.6  VS Under-Voltage (UV) Condition
      7. 8.3.7  VS Over-Voltage (OV) Condition
      8. 8.3.8  Switch Inputs Settings
        1. 8.3.8.1 Input Current Source and Sink Selection
        2. 8.3.8.2 Input Mode Selection
        3. 8.3.8.3 Input Enable Selection
        4. 8.3.8.4 Thresholds Adjustment
        5. 8.3.8.5 Wetting Current Configuration
      9. 8.3.9  Interrupt Generation and INT Assertion
        1. 8.3.9.1 INT Pin Assertion Scheme
        2. 8.3.9.2 Interrupt Idle Time (tINT_IDLE) Time
        3. 8.3.9.3 Microcontroller Wake-Up
        4. 8.3.9.4 Interrupt Enable or Disable and Interrupt Generation Conditions
        5. 8.3.9.5 Detection Filter
      10. 8.3.10 Temperature Monitor
        1. 8.3.10.1 Temperature Warning (TW)
        2. 8.3.10.2 Temperature Shutdown (TSD)
      11. 8.3.11 Parity Check and Parity Generation
      12. 8.3.12 Cyclic Redundancy Check (CRC)
    4. 8.4 Device Functional Modes
      1. 8.4.1 Continuous Mode
      2. 8.4.2 Polling Mode
        1. 8.4.2.1 Standard Polling
        2. 8.4.2.2 Matrix polling
      3. 8.4.3 Additional Features
        1. 8.4.3.1 Clean Current Polling (CCP)
        2. 8.4.3.2 Wetting Current Auto-Scaling
        3. 8.4.3.3 VS Measurement
        4. 8.4.3.4 Wetting Current Diagnostic
        5. 8.4.3.5 ADC Self-Diagnostic
    5. 8.5 Programming
      1. 8.5.1 SPI Communication Interface Buses
        1. 8.5.1.1 Chip Select ( CS)
        2. 8.5.1.2 System Clock (SCLK)
        3. 8.5.1.3 Slave In (SI)
        4. 8.5.1.4 Slave Out (SO)
      2. 8.5.2 SPI Sequence
        1. 8.5.2.1 Read Operation
        2. 8.5.2.2 Write Operation
        3. 8.5.2.3 Status Flag
    6. 8.6 Register Maps
    7. 8.7 Programming Guidelines
  9. 9 Application Information Disclaimer
    1. 9.1 Application Information
    2. 9.2 Using TIC12400-Q1 in a 12 V Automotive System
    3. 9.3 Resistor-coded Switches Detection in Automotive Body Control Module
      1. 9.3.1 Design Requirements
      2. 9.3.2 Detailed Design Procedure
      3. 9.3.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Support Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

8.4.3.2 Wetting Current Auto-Scaling

The 10 mA and 15 mA wetting current settings are useful to clean oxide build-up on the mechanical switch contact surface when the switch changes state from open to close. After the switch is closed, it is undesirable to keep the wetting current level at high level if only digital switches are monitored since it results in high current consumption and could potentially heat up the device quickly if multiple inputs are monitored. The wetting current auto-scaling feature helps mitigate this issue.

When enabled (AUTO_SCALE_DIS_CSO or AUTO_SCALE_DIS_CSI bit = logic 0 in the WC_CFG1 register), wetting current is reduced to 2 mA from 10 mA or 15 mA setting after switch closure is detected. The threshold used to determine a switch closure is the threshold configured in the THRES_COMP register for inputs configured as comparator input mode. For inputs configured as ADC input mode, the threshold used to determine a switch closure depends on the input number, as described in Table 8-8 below.

Table 8-8 Threshold Used to Determine a Switch Closure for Wetting Current Auto-scaling for ADC Inputs
INPUTTHRESHOLD USED TO DETERMINE A SWITCH CLOSURE
IN0-IN11Mapped threshold from THRES0 to THRES7
IN12 to IN17THRES2B
IN18 to IN22THRES3C
IN23THRES9

The current reduction takes place N cycles after switch closure is detected on an input, where N depends on the setting of the DET_FILTER bits in the CONFIG register:

  • DET_FILTER= 00: wetting current is reduced immediately in the next detection cycle after a closed switch is detected.
  • DET_FILTER= 01: wetting current is reduced when a closed switch is detected and the switch status is stable for at least 2 consecutive detection cycles.
  • DET_FILTER= 10: wetting current is reduced when a closed switch is detected and the switch status is stable for at least 3 consecutive detection cycles.
  • DET_FILTER= 11: wetting current is reduced when a closed switch is detected and the switch status is stable for at least 4 consecutive detection cycles.

The wetting current is adjusted back to the original setting of 10 mA or 15 mA at a time of N cycles after an open switch is detected, where N again depends on the DET_FILTER bit setting in the CONFIG register. Figure 8-20 depicts the behavior of the wetting current auto-scaling feature.

GUID-E6FB81EA-D1B4-4F56-8072-4F6746290770-low.gifFigure 8-20 Wetting Current Auto-scaling Behavior

The wetting current auto-scaling only applies to 10 mA and 15 mA settings and is only available in continuous mode. If AUTO_SCALE_DIS_CSO or AUTO_SCALE_DIS_CSI bit is set to logic 1 in the WC_CFG1 registers, the wetting current stays at its original setting when a closed switch is detected. Power dissipation needs to be closely monitored when wetting current auto-scaling is disabled for multiple inputs as the device could heat up quickly when high wetting current settings are used. If the auto-scaling feature is disabled in continuous mode, the total power dissipation can be approximated using Equation 1.

Equation 1. GUID-36A0BC3E-1AA3-4F7C-93AF-CF63FF80B64E-low.gif

where IWETT (TOTAL) is the sum of all wetting currents from all input channels. Increase in device junction temperature can be calculated based on P × RθJA. The junction temperature must be below TTSD for proper device operation. An interrupt will be issued when the junction temperature exceeds TTW or TTSD. For detailed description of the temperature monitoring, please refer to sections Temperature Warning (TW) and Temperature Shutdown (TSD).