SDAA370 May   2026 UCC34141

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 End-Equipment Traction Inverter
    2. 1.2 Why is Safety Needed in Inverter?
    3. 1.3 FuSa Development Flow
      1. 1.3.1 V-Model Development
      2. 1.3.2 Inverter Safety Lifecycle
  5. 2FuSa Requirements for Traction Inverter
    1. 2.1 Traction Inverter Structure and Function Introduction
    2. 2.2 FuSa Requirements Derivation Process
    3. 2.3 Safety Goal
    4. 2.4 FuSa Concept
      1. 2.4.1 FSC Design Architecture
      2. 2.4.2 Fault Tree Analysis
      3. 2.4.3 FuSa Requirement
    5. 2.5 Technical Safety Concepts
      1. 2.5.1 TSC Design Architecture
      2. 2.5.2 Failure Mode and Effect Analysis
      3. 2.5.3 Technical Safety Requirements
  6. 3Safety Design Implementation on Inverter
    1. 3.1 TI FuSa Product
    2. 3.2 How Does TSR Implement?
      1. 3.2.1 Position Sensor
      2. 3.2.2 MCU
      3. 3.2.3 Logic Circuit
      4. 3.2.4 Smart Isolated Gate Driver
    3. 3.3 Dependent Failure Consideration
    4. 3.4 Detailed FuSa Design Structure for Traction Inverter
    5. 3.5 Achieving FuSa Requirements with TI Safety Devices
      1. 3.5.1 MCU
      2. 3.5.2 Gate Driver
        1. 3.5.2.1 Gate Monitor Circuit and Over Current Protection
        2. 3.5.2.2 Other Safety Mechanisms in UCC5881-Q1
      3. 3.5.3 Isolated bias supply
        1. 3.5.3.1 Centralized LV Isolated Power Supply Architecture
        2. 3.5.3.2 Fully Distributed LV Isolated Power Supply Architecture
        3. 3.5.3.3 Semi-Distributed LV Isolated Power Supply Architecture
        4. 3.5.3.4 HV Isolated Bias Supply
        5. 3.5.3.5 TI's Design for Isolated Bias Supply in Traction Inverter
      4. 3.5.4 Power Management IC
        1. 3.5.4.1 Multiple Paths Power Rail with Protection and Independent Thermal Shut-Down
        2. 3.5.4.2 Power Rail Voltage Monitoring
        3. 3.5.4.3 MCU Fault Monitor and other Protection Mechanisms
      5. 3.5.5 Position Sensor
      6. 3.5.6 Current Sensor
      7. 3.5.7 Voltage Sensor
        1. 3.5.7.1 Isolated DC Voltage Sensing
        2. 3.5.7.2 Non-Isolated DC voltage sensing
      8. 3.5.8 Temperature Sensor
  7. 4Summary
  8. 5References

3.2.4 Smart Isolated Gate Driver

The UCC5881-Q1 is an isolated, highly configurable adjustable drive strength gate driver targeted to drive high power SiC MOSFETs and IGBTs. It is a TI FuSa-Compliant device developed with ISO26262:2018 and is fully validated. Documentation is available to aid ISO26262: 2018 system design up to ASIL-D with numerous integrated safety mechanisms.

UCC5881-Q1 features dedicated hardware ASC pins on both primary side and secondary side. This active short circuit function allows the system to force the state of the power transistor regardless of the PWM input. For cases where the main MCU is unavailable due to fault or other reasons, a secondary control circuit drives the ASC_EN input high to force the output of the device to the state defined by the ASC pin input. Figure 3-9 illustrates the typical ASC implementation diagram with the UCC5881-Q1. The ASC circuit is also detected by BIST to ensure its proper functioning.

Table 3-1 presents the input truth table for the safe state pins, showing how different combinations of inputs determine the output state. Beyond these basic functions, the ASC can be flexibly configured as a high-priority event that overrides certain other failures (such as DESAT, shoot-through, SPI fault, etc.). The secondary side ASC can also force the system to enter a safe state regardless of UCC5881-Q1 primary side power faults and other PWM/communication-related faults. More detailed information is available in the UCC5881-Q1 datasheet.

ASC Implementation with UCC5881-Q1Figure 3-9 ASC Implementation with UCC5881-Q1
Table 3-1 Truth Table of the UCC5881-Q1 Safe State Pins
INP INN ASC_EN_SEC ASC_SEC ASC_EN_PRI ASC_PRI Output State
0 0 0 x 0 x Low
1 0 0 x 0 x High
x 1 0 x 0 x Low
x x 1 0 x x Low
x x 1 1 x x High
x x 0 x 1 0 Low
x x 0 x 1 1 High

The shoot-through protection (STP) function of the UCC5881-Q1 provides an additional layer of protection against shoot-through conditions that might arise from incorrect PWM commands from the MCU. If an over-current or power module short-circuit event occurs despite this protection, the UCC5881-Q1 will report it through the DESAT signal, which is also monitored by BIST.

In traction inverter safety design applications, the external ASC signal (from both the MCU and external logic circuits) is routed to either the UCC5881-Q1 primary side ASC pin or the secondary side ASC pin. This configuration ensures that the gate driver output operates independently from the PWM input when necessary, generating the appropriate safe state output to the power module. Both the PWM signal and ASC signal are protected with isolation lane detection safety mechanisms to address potential isolation lane failures. Based on these FuSa features, the system can meet the TSR related to FSR 1.6 using TI's safety-oriented devices.