TIDUF61 May   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 TLV9002-Q1
      2. 2.2.2 TLV9034-Q1
      3. 2.2.3 TPS7B69-Q1
      4. 2.2.4 SN74HCS08-Q1
      5. 2.2.5 SN74HCS86-Q1
    3. 2.3 System Design Theory
      1. 2.3.1 TIDA-0020069 Operation
        1. 2.3.1.1 Constant Current Source
          1. 2.3.1.1.1 Design Goals
          2. 2.3.1.1.2 Design Description
          3. 2.3.1.1.3 Design Notes
          4. 2.3.1.1.4 Design Steps
        2. 2.3.1.2 Current Sensing
          1. 2.3.1.2.1 Design Goals
          2. 2.3.1.2.2 Design Description
          3. 2.3.1.2.3 Design Steps
        3. 2.3.1.3 Load Connections and Clamps
        4. 2.3.1.4 Modified Window Comparator
        5. 2.3.1.5 Digital Logic Gates
      2. 2.3.2 Status Indication
        1. 2.3.2.1 Normal Operation (Closed Connection) State
        2. 2.3.2.2 Open Connection State
        3. 2.3.2.3 Short-to-Battery State
        4. 2.3.2.4 Short-to-Ground State
  9. 3Hardware, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1. 3.3.1 Normal Operation (Closed Connection) Test Results
      2. 3.3.2 Open Connection Test Results
      3. 3.3.3 Short-to-Battery Test Results
      4. 3.3.4 Short-to-Ground Test Results
      5. 3.3.5 Disable (Shutdown) Test Results
  10. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  11. 5Tools and Software
  12. 6Documentation Support
  13. 7Support Resources
  14. 8Trademarks
  15. 9About the Author

2.3.2.3 Short-to-Battery State

The TIDA-020069 is in a short-to-battery state when a short to the 12V battery voltage is inserted at any point within the interlock loop. This short can be inserted between HVIL-Send and the load, between any load resistors (HV connectors), or between the load and HVIL-Return. During this state, the onboard LED marked Short to Battery is turned on, as shown in the test results image. This short-to-battery state can be the result of improper wiring connections, deteriorating connectors, or problems mishandling during servicing, where the 12V battery is shorted to the interlock pins. This state represents a failure mode and the TIDA-020069 is indicating that the high-voltage battery of the HEV/EV needs to be disabled immediately.

Figure 2-17 illustrates the expected behavior of HVIL-Send and HVIL-Return during the short-to-battery failure state. The high-voltage connectors are modeled as resistors connected in series with the TIDA-020069, but a short to the 12V battery was inserted into the interlock loop.

TIDA-020069 Interlock Line Short to 12V Battery Figure 2-17 Interlock Line Short to 12V Battery

In this failure state, both the HVIL-Send and HVIL-Return voltages are pulled high. The clamping diodes of the Section 2.3.1.3 portion of the design clamp HVIL-Send and HVIL-Return to 5V (the supply voltage regulated by TPS7B69-Q1). This prevents an overvoltage effect and protects downstream devices that can be connected to HVIL-Send and HVIL-Receive, like an MCU.

The differential voltage, VDIF, between HVIL-Send and HVIL-Return is very small in this failure mode, regardless of where the short is inserted within the interlock loop. HVIL-Send and HVIL-Return must both be greater in voltage than the Upper Threshold voltage for the TIDA-20069 state logic to work correctly. However, both HVIL-Send and HVIL-Return are higher in voltage in this state than HVIL-SendNormal Operation and HVIL-SendOpen Connection. Therefore, there are no additional design requirements for this state that are not already met by the design guidelines of Section 2.3.2.1 and Section 2.3.2.2.

The results of this state can be verified in the Test Results section.