TIDUF43 August   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Terminology
    2. 1.2 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 TPS1213-Q1 45V, Low IQ, Automotive High-Side Switch Controller With Low-Power Mode and Adjustable Load Wakeup Trigger
      2. 2.3.2 INA296x-Q1 AEC-Q100, –5V to 110V, Bidirectional, 1.1MHz, 8V/μs, Ultra-Precise Current-Sense Amplifier
  9. 3System Design Theory
    1. 3.1 Low-Power Mode Considerations
    2. 3.2 Precharge Circuit Considerations
    3. 3.3 Short-Circuit Protection
    4. 3.4 LM74704-Q1 Enable
    5. 3.5 Headers
      1. 3.5.1 Headers for Configuring INA296B-Q1
      2. 3.5.2 Headers for Configuring TPS1213-Q1
    6. 3.6 Software Considerations
      1. 3.6.1 Fuse Channel Definition
      2. 3.6.2 Software Functions
    7. 3.7 Optional Output TVS Diode
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
    2. 4.2 Software
    3. 4.3 Test Setup
    4. 4.4 Test Results
      1. 4.4.1 State Transition
      2. 4.4.2 System IQ in Low-Power Mode
      3. 4.4.3 Precharge Test
      4. 4.4.4 Overcurrent Protection
      5. 4.4.5 PWM Overcurrent
      6. 4.4.6 Short-Circuit Protection
      7. 4.4.7 Thermal Testing
      8. 4.4.8 CISPR-25 Emissions Testing
        1. 4.4.8.1 Conducted Emissions Testing
        2. 4.4.8.2 Radiated Emissions Testing
        3. 4.4.8.3 Summary of Results
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
      3. 5.1.3 PCB Layout Recommendations
        1. 5.1.3.1 Layout Prints
      4. 5.1.4 Altium Project
      5. 5.1.5 Gerber Files
      6. 5.1.6 Assembly Drawings
    2. 5.2 Documentation Support
    3. 5.3 Support Resources
    4. 5.4 Trademarks
  12. 6About the Author

2.2 Design Considerations

The TPS1213-Q1 high-side switch controller is able to drive an external main power-path FET and an external low power path FET with the use of the nLPM and INP control inputs. See Table 3-2 for information on how nLPM and INP are used to control the low power path and main power path FETs.

Table 2-1 TPS1213-Q1 INP and nLPM Truth Table
PARAMETERS

INP (LOW)

INP (High)
nLPM (Low) Pulling nLPM low forces the TPS1213-Q1 into low power mode, drives the low power path FET (Q3), and enables automatic load-wakeup. Pulling nLPM low forces the TPS1213-Q1 into low power mode, drives the low power path FET (Q3), and enables automatic load-wakeup.
nLPM (High) Pulling nLPM high forces the TPS1213-Q1 into active mode. Pulling INP low turns off the FET of the main power path (Q2). Pulling INP high turns on the main power path (Q2) if nLPM is high.

When discussing vehicle states, using the low power path is analogous to leaving a vehicle in parked (key-off) mode to minimize power consumption. When the vehicle is driving, ECUs need to run at normal operation, so the main path is used to support and protect higher current loads. The TPS1213-Q1 also features automatic load wakeup to quickly transition from low-power mode to active mode when the load current exceeds the configurable load wakeup threshold. All components were selected to minimize the IQ during low-power-mode operation. The TPS22919-Q1 load switch was used to disable the INA296B-Q1 in low power mode to further reduce system IQ.

For capacitive loads that incur large inrush currents, a gate slew-rate limiting circuit was added on the gate of the low power path so at start-up, the load capacitors can be charged by slowly driving the gate high. Precharging the load capacitors using this method limits the inrush current and prevents false shutdowns from the various time-current characteristics defined for this design.

The INA296B-Q1 and MSPM0L1306-Q1 devices were selected to implement the I2t Fuse Algorithm. The INA296B-Q1 features precise current sense, which is fed to an ADC peripheral in the MSPM0L1306-Q1. By constantly monitoring the current in active mode, overload events promptly shut down the output according to the software-based I2t fuse algorithm to protect the wire harnesses and load. Short-circuit protection is also featured in this design through the TPS1213-Q1; the TPS1213-Q1 monitors the VDS of the main FET and signals a fault when VDS exceeds a value configurable in hardware.

Finally, the INA296B-Q1 has both unidirectional and bidirectional current sensing capabilities, making this design fit for many kinds of loads including resistive, capacitive, and inductive loads. Reverse current can be monitored through the TPS1213-Q1 but requires removal of the LM74704-Q1 ideal diode control to allow reverse current to the power supply.