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

2.3.2.4 Short-to-Ground State

The TIDA-020069 is in a short to ground state when a short to ground has been 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 Ground is turned on, as shown in the test results image. This short-to-ground state can be the result of improper wiring connections, deteriorating connectors, or problems mishandling during servicing, where ground 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 2-18 illustrates the expected behavior of HVIL-Send and HVIL-Return during the short-to-ground failure state. The high-voltage connectors are modeled as resistors connected in series with the TIDA-020069, but a short to ground was inserted into the interlock loop.

TIDA-020069 Interlock Line Short Circuit to Ground Figure 2-18 Interlock Line Short Circuit to Ground

In this failure state, both the HVIL-Send and HVIL-Return voltage are pulled low. The clamping diodes of the Section 2.3.1.3 portion of the design clamp HVIL-Send and HVIL-Return to ground and prevent these pins from getting pulled any lower than ground. This prevents an undervoltage effect and protects downstream devices that can be connected to HVIL-Send and HVIL-Receive, like an MCU.

Unlike the Short-to-Battery failure mode, the differential voltage, VDIF, between HVIL-Send and HVIL-Return has a noticeable variation, depending on the location of where the short is inserted within the interlock loop. In Figure 2-18, both HVIL-Send and HVIL-Return are lower in voltage in this state than the Lower Threshold voltage. However, the voltage of HVIL-Send can vary in the failure state, depending on the location of the ground short. When the ground short occurs between the HVIL-Send node and the first load resistance, HVIL-Send is pulled to ground. When the ground short is inserted closer to the HVIL-Return node, the voltage at HVIL-Send increases. This HVIL-Send voltage can increase above the Lower Threshold voltage level. For proper operation of the TIDA-020069, HVIL-Send must be less than the Upper Threshold voltage level and HVIL-Return must be less than the Lower Threshold voltage level.

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