The TPS51113-EVM contains a 20-Ω series resistor
in the feedback loop for loop response analysis.
- Set up the EVM as described in Section 8.1 and Figure 7-2.
- Connect the isolation transformer to test points
marked TP4 and TP3.
- Connect an input signal amplitude measurement
probe (channel A) to TP4.
- Connect an output signal amplitude measurement
probe (channel B) to TP3. Connect the ground lead of channel A and channel B to
TP9 and TP10.
- Inject around 40-mV or less signal through the
isolation transformer.
- Sweep the frequency from 100 Hz to 1 MHz with a
10-Hz or lower post filter. The control loop gain and phase margin can be
measured.
- Disconnect the isolation transformer from the
bode plot test points before making other measurements (Signal injection into
feedback may interfere with accuracy of other measurements).