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Cleverscope CS328A FRA Measurement System for TI TPS55340 EVM With Jensen VB-1BB Isolation Transformer

A high-precision Frequency Response Analyzer (FRA) setup using the Cleverscope CS328A oscilloscope and Jensen VB-1BB isolation transformer, designed to evaluate the stability and control loop behavior of switch-mode power supplies like the TI TPS55340 EVM. It enables in-system gain and phase margin testing with excellent noise rejection..

  • Detail
  • Special Features
  • Specification

The Cleverscope CS328A was configured for Frequency Response Analysis (FRA) of the TI TPS55340 flyback converter EVM by injecting a small AC signal across a modified 50Ω resistor in the feedback path. The setup includes:

  • Signal injection via Jensen VB-1BB transformer

  • Sweep range from 7.6 Hz to 200 kHz

  • Excitation voltage: ~11–13 mV peak, optimized adaptively

  • Channel A (TP6) reads the injected signal

  • Channel B (TP2) captures the power supply’s response

  • Signal coherence and gain/phase measured using the Cleverscope FRA application (v4.672)

The system proved to be highly accurate, delivering phase margins around 60° and gain margins up to -19 dB, depending on line/load conditions. These results were validated against both TI's own analysis and Venable equipment.

  • Narrow band correlation for noise-free FRA readings

  • Adaptive low-level signal injection (as low as 10–13 mV)

  • Accurate gain/phase margin analysis on actual power supply boards

  • Software-controlled log sweep with 20 steps/decade

  • Supports both low line (8V) and high line (24V) operation conditions

  • Matches benchmark results from TI and Venable analyzers

  • Real-time phase margin slope and stability visualization

  • Built-in moving average and Hanning filters for signal clarity

  • Non-intrusive testing that avoids system disturbance

Parameter Details
Oscilloscope Model Cleverscope CS328A
Software Version v4.672
Isolation Transformer Jensen VB-1BB (1:1 video transformer)
Signal Injection Resistor 50 Ω (modified R3 on EVM)
Excitation Voltage 10–13 mV peak
Frequency Sweep Range 7.6 Hz – 200 kHz
Sweep Type Logarithmic, 20 steps/decade
FRA Method Synchronous gain/phase correlation
Noise Filtering 1.28 μs moving average, Hanning window
ADC Resolution 14-bit
Load Conditions Tested 2.5 A (2 Ω), 1 A (5 Ω)
Operating Input Voltages 8V (low line), 12V (nominal), 24V (high line)
Gain Margin (GM) Range -9.2 dB to -19 dB
Phase Margin (PM) Range 50.8° to 74.4°