SLVUCK7A november   2022  – july 2023 TPSF12C1 , TPSF12C1-Q1

 

  1.   1
  2.   Description
  3.   Get Started
  4.   Features
  5.   Applications
  6.   6
  7. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specifications
    4. 1.4 Device Information
  8. 2Hardware
    1. 2.1 EVM Description
    2. 2.2 Setup
      1. 2.2.1 High-Voltage Testing
      2. 2.2.2 EVM Connections
      3. 2.2.3 Low-Voltage Testing
    3. 2.3 Header Information
    4. 2.4 EVM Performance Validation
    5. 2.5 AEF Design Flow
      1. 2.5.1 AEF Circuit Optimization and Debug
  9. 3Implementation Results
    1. 3.1 EMI Performance
    2. 3.2 Thermal Performance
    3. 3.3 Surge Immunity
    4. 3.4 SENSE and INJ Voltages
    5. 3.5 Insertion Loss
  10. 4Hardware Design Files
    1. 4.1 Schematic
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout
      1. 4.3.1 Assembly Drawings
      2. 4.3.2 Multi-Layer Stackup
  11. 5Compliance Information
    1. 5.1 Compliance and Certifications
  12. 6Additional Information
    1.     Trademarks
  13. 7Related Documentation
    1. 7.1 Supplemental Content
  14. 8Revision History

2.5.1 AEF Circuit Optimization and Debug

Here are some considerations and best practices to optimize AEF circuit operation:

  1. If the EMI measurement with AEF enabled is not performing as expected, then probe the TPSF12C1 INJ pin voltage while the regulator is switching. Verify that the INJ voltage is not getting clipped near the positive or negative supply rails, as mentioned in step 4 of Section 2.4.
    • If the INJ voltage is getting clipped, then increase the regulator-side Y-capacitance and/or the inject capacitance. Then recheck loop stability using the TPSF12C1 quickstart calculator or by simulation.
  2. The metallic chassis structure is a critical part of the overall filter implementation. The filter PCB typically mounts to the chassis structure using several screw attachments, and the chassis serves to connect the various GND nodes on the filter PCB. These nodes are not explicitly connected with PCB copper and instead rely on the chassis to complete the electrical connection. As such, the chassis becomes the lowest impedance return path for CM noise current.
    • When testing a power system that includes a chassis as illustrated in Figure 3-2, CM noise can capacitively couple to the reference ground plane of the EMI measurement setup and thus bypass a filter circuit that is not closely referenced to the ground plane. In this case, TI recommends bonding the GND plane of the filter EVM directly to the reference ground plane. This also serves to minimize parasitic inductance in the GND connection to the AEF circuit. CM noise current emanating from the power stage then gets recirculated by the low shunt impedance of the Y-capacitors (both active and passive), thereby preventing noise from reaching the LISN.
  3. Based on the amplification of the effective Y-capacitance, AEF enables a reduction of the CM choke inductance while maintaining the same LC corner frequency and CM attenuation characteristic. However, a choke with reduced CM inductance and smaller size typically has a lower leakage inductance, which is responsible for DM attenuation along with the X-capacitors.
    • If the DM inductance is significantly reduced when using smaller CM chokes, then increase the X-capacitance or add a small discrete inductor to obtain sufficient DM attenuation. Otherwise, a high DM noise component (relative to the CM component) can dominate the total noise measurement, thereby concealing the impact of AEF on CM noise mitigation.
  4. Typical values for the sense and inject capacitances are 680 pF and 4.7 nF, respectively. Depending on the final implementation in the target application, the default damping and compensation component values installed on the EVM can require modification by the user to achieve acceptable loop stability. Ferrite chokes are inherently more difficult to stabilize than nanocrystalline.
    • For additional context pertaining to component selection and circuit optimization, refer to the TPSF12C1 product data sheet and the TPSF12C1 quickstart calculator.