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

3.2 Test Setup

This reference design only requires a single 12V power supply for operation and testing. Onboard LED indicators are included in this design to visually display the state of the interlock. These LEDs are marked: Normal Operation, Open Connection, Short to Battery, and Short to Ground and turn on to indicate the corresponding state of the HVIL signal load.

TIDA-020069 TIDA-020069 Test Setup Figure 3-5 TIDA-020069 Test Setup

Multiple states are replicated and tested with this reference to verify both normal operation and the ability to diagnose different interlock states. The design features four 50Ω resistors that represent the impedance of HVIL connectors. These load resistors can be connected in series, left with an open connection, or have a short inserted between them. PCB jumper shorts are used with PCB header pins to configure the different modes of operation.

Figure 3-6 shows where different pin headers are located on the PCB. The 1 × 5 pin header columns labeled J1-1 and J1-2 are connected to each endpoint of load resistors: RLoad1, RLoad2, RLoad3, and RLoad4. Connecting all five rows of J1-1 to J1-2 together with 2-pin PCB shunt connectors creates a series connection between all four load resistors. This is the connection used for the Normal Operation condition. Disconnecting any 2-pin PCB shunt connectors between J1-1 and J1-2 creates an open connection (disconnect), which is used for the Open Connection condition.

The 1 × 5 pin header column labeled J2 has a short between all pins, causing J2 to behave like a supply voltage bus rail. The 1 × 3 pin header column labeled J3 has row 1 connected to the 12V supply input, row 2 connected to J2, and row 3 connected to ground. When a single 2-pin PCB shunt connector is connected between row 1 and row 2 of J3, J2 becomes a bus rail to the 12V supply voltage. When a single 2-pin PCB shunt connector is connected between row 2 and row 3 of J3, J2 becomes a bus rail to the ground supply voltage. A 3-pin PCB shunt connectors between columns J2, J1-1, and J1-2, inserts a short to either the 12V supply voltage or ground supply to the corresponding row. This short can be inserted either before the four load resistors,in-between any of the resistors, or after the load.

The 3 × 1 pin header row labeled J4 is used to control the shutdown functionality of the board. Column 1 is connected to the 5V voltage through the pullup resistor R8. Column 2 is connected to the base of transistor Q2, which is operating as a switch. Column 3 is connected to the ground supply voltage. When a 2-pin PCB shunt connector is inserted between column 1 and 2, the shutdown functionality is turned on (active high), and the current source enters shutdown mode. When a 2-pin PCB shunt connector is inserted between column 2 and 3, the shutdown functionality is inactive (active low), and the system operates as anticipated.

TIDA-020069 TIDA-020069 PCB Header Connections Figure 3-6 TIDA-020069 PCB Header Connections

DC voltage and current measurements were taken with a digital multimeter at numerous points on the board. The following test points were measured during multiple modes of operation: 5V_LDO TP, HVIL-Send TP, HVIL-Return TP, HVIL-Send Logic-Higher TP, HVIL-Send Logic-Lower TP, HVIL-Return Logic-Higher TP, HVIL-Higher Logic-Lower TP, and CS-Output. The test results are located in the following section, Test Results.