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

2.4.5 STO_FB Signal Flow Path

The ISO7710 is a reinforced digital isolator which receives the input signal STO_FB_EN and operates with TIOS1013 (a push-pull driver) to provide feedback signal STO_FB (Logic high = 24 V) to safe PLC. STO_FB_EN is the output signal of the OR gate SN74AHC1G32 which receives the dual-channel feedback signal STO_1_FB and STO_2_FB. Figure 2-14 shows the schematic.

GUID-20220307-SS0I-QNLN-CKKH-JJS7WC0M0T8B-low.pngFigure 2-14 STO_FB Feedback Monitor Schematic

The STO_1_FB is the output of the load switch TPS22919 (controls the primary side VCC1 of the gate driver) and the STO_1_FB connects to the gate of Q5 with the resistors divided network (R54|R55 – 1.4 kΩ|1 kΩ) to synchronize the switching threshold of STO_1_FB with maximum UVLO1 threshold-voltage of gate driver ISO5852S (or ISO5452). According the data sheet of FET Q5 CSD13383F4 and gate driver ISO5852S (or ISO5452), the VGS (th) min = 0.7 V, VIT+(UVLO1) = 2.25 V, then to simulate the switching threshold. The logic 0 (OFF) for STO_1_FB is from 0-V to 2-V and Logic 1 (ON) is from 2 V to 3.9 V (3.9 V is maximum voltage of P3V3). The V GS = 1.37 V during ON state with 1.6-mA IDS current thanks to the limit resistor R52 (2 kΩ).

The STO_2_FB is the output of the load switch TPS27S100 (controls the secondary side VCC2 of gate driver via TIDA-00199 safe power supply) and the STO_2_FB connects to the gate of Q4 with the resistors divided network (R48|R50 – 154 kΩ|10 kΩ) to synchronized the switching threshold of STO_2_FB with maximum UVLO threshold-voltage of the TIDA-00199 design. According the data sheet of FET Q4 CSD13383F4 and TIDA-00199 design guide, the VGS (th) min = 0.7 V, VOFF(UVLO) = 14 V, then to simulate the switching threshold. The logic 0 (OFF) for STO_2_FB is from 0 V to 14 V and Logic 1 (ON) is from 14 V to 28.8 V (28.8 V is maximum voltage of P24-V). The VGS = 1.46 V during ON state with 1.65 mA IDS current due to the limit resistor R47 (2 kΩ).