SLVUD37 December   2024 TPS62968

 

  1.   1
  2.   Description
  3.   Features
  4.   Applications
  5.   5
  6. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
    5. 1.5 Cautions and Warnings
  7. 2Hardware
    1. 2.1 Setup
      1. 2.1.1 Input and Output Connector Descriptions
  8. 3Implementation Results
    1. 3.1 Test Results
    2. 3.2 Ripple Measurement Setup
    3. 3.3 Modifications
      1. 3.3.1 Input and Output Capacitors
      2. 3.3.2 Configurable Enable Threshold Voltage
      3. 3.3.3 NR/SS Capacitor
      4. 3.3.4 Feedforward Capacitor
      5. 3.3.5 S-CONF Resistor
      6. 3.3.6 Loop Response Measurement
      7. 3.3.7 Single LC Filter Operation
    4. 3.4 Performance Specification
  9. 4Hardware Design Files
    1. 4.1 Schematic
    2. 4.2 PCB Layout
    3. 4.3 Bill of Materials
  10. 5Additional Information
    1. 5.1 Trademarks

3.3.6 Loop Response Measurement

The loop response can be measured with simple changes to the circuitry. First, cut the short section of trace on the bottom layer between the pads of R5 resistor. Second, cut the trace on the bottom layer that connects to R8. These changes are shown in Figure 3-2. Third, install a 49.9Ω resistor across R5 pads on the back of the PCB and install a 0Ω resistor across R8 pads on the back of the PCB. The pads are spaced to allow installation of a 0603-sized resistors. Lastly, replace the ferrite bead (FB1) with a 0Ω resistor and remove any second LC stage output capacitors C19 to C23. The second LC filter must be removed to break the complete feedback loop and measure the loop response. With these changes, an AC signal (10mV, peak-to-peak amplitude recommended) can be injected into the control loop across the added 49.9Ω resistor.

TPS62968EVM Loop Response Measurement Modification (Bottom Layer)Figure 3-2 Loop Response Measurement Modification (Bottom Layer)