TIDUDS9B December   2017  – November 2022

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Conditions of Use: Assumption
        1. 2.2.1.1 Generic Assumptions
        2. 2.2.1.2 Specific Assumptions
      2. 2.2.2 Diagnostics Coverage
        1. 2.2.2.1 Dual-Channel Monitoring
        2. 2.2.2.2 Checking ISO1211 Functionality With MCU (SIL1)
        3. 2.2.2.3 Checking TPS22919 Functionality With MCU (SIL1)
        4. 2.2.2.4 Checking TPS27S100 Functionality With MCU (SIL1)
        5. 2.2.2.5 Optional Monitoring Using RDY Pin of ISO5452, ISO5852S or UCC21750 Integrated Analog-to-PWM Isolated Sensor
      3. 2.2.3 Drive State
    3. 2.3 Highlighted Products
      1. 2.3.1 ISO1211
      2. 2.3.2 TPS27S100
      3. 2.3.3 TPS22919
      4. 2.3.4 ISO5852S, ISO5452
    4. 2.4 System Design Theory
      1. 2.4.1 Digital Input Receiver for STO
      2. 2.4.2 STO_1 Signal Flow Path for Controlling VCC1
      3. 2.4.3 STO_2 Signal Flow Path
        1. 2.4.3.1 High-Side Switch for Controlling Secondary-Side Supply Voltage of Gate Driver
        2. 2.4.3.2 Powering up Secondary Side: VCC2 of Gate Driver
      4. 2.4.4 Gate Driver Design
      5. 2.4.5 STO_FB Signal Flow Path
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Getting Started Hardware
      1. 3.1.1 PCB Overview
    2. 3.2 Testing and Results
      1. 3.2.1 Logic High and Logic Low STO Thresholds
      2. 3.2.2 Validation of STO1 Signal
        1. 3.2.2.1 Propagation of STO1 to VCC1 of Gate Driver
        2. 3.2.2.2 1-ms STO Pulse Rejection
        3. 3.2.2.3 Diagnostic Pulses From MCU Interface
      3. 3.2.3 Validation of STO2 Signals
        1. 3.2.3.1 Propagation of STO2 to VCC2 of Gate Driver
        2. 3.2.3.2 1-ms Pulse Rejection
        3. 3.2.3.3 Diagnostic Pulses From MCU
        4. 3.2.3.4 Inrush Current Measurement
      4. 3.2.4 3.3-V Voltage Rail From Switcher
      5. 3.2.5 60-V Input Voltage and Reverse Polarity Protection
      6. 3.2.6 Validation of Trip Zone Functionality
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 Layer Plots
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  10. 5Related Documentation
    1. 5.1 Trademarks
  11. 6About the Author
  12. 7Recognition
  13. 8Revision History

2.4.3.1 High-Side Switch for Controlling Secondary-Side Supply Voltage of Gate Driver

The TPS27S100x is a single-channel, fully-protected, high-side switch with an integrated NMOS and charge pump. An external adjustable current limit improves the reliability of the whole system by clamping the inrush or overload current. Figure 2-12 shows the schematic design of the TPS27S100.

GUID-20220307-SS0I-XFQB-RCCS-RJR5GHQSD2Z2-low.png Figure 2-12 TPS27S100 Schematic

The device power supply is 24-V which is assumed to be protected against fault and remains within ±20% tolerance. Pin 3 Enable the control for channel activation by signal STO2_EN.

Equation 6 calculates the value of resistor R4, which is required to keep the 1-A nominal current in the 0- to 3.3-V current-sense range. To achieve better current-sense accuracy, a 1% tolerance or better resistor is preferred.

Equation 6. GUID-42F50C89-F9B9-4B73-932A-4AD2DC3DC6B6-low.gif

The value of resistor R4 is selected as 1.65 K. The current-sense (CS) pin is connected to the ADC input of the diagnostic MCU (SIL 1) with a low-pass filter (R3 and C6).

To set the adjustable current limit value at 1 A, calculate R7 using Equation 7.

Equation 7. GUID-C3618392-0E2E-4619-A675-9349887CA5A7-low.gif

The value of resistor R7 is selected as 2.55 kΩ.

The enable pin is permanently connected to 3.3 V to enable continuous diagnostic monitoring and also send back to the diagnostic MCU (SIL 1).