Follow these steps to measure the control loop gain and phase on the TPS40193EVM-001.

1. Connect 1-kHz to 1-MHz isolation transformer to TP12 and TP13 as shown in Figure 5-3.
2. Connect input signal amplitude measurement probe (Channel A) to TP12 as shown in Figure 5-3.
3. Connect output signal amplitude measurement probe (Channel B) to TP13 as shown in Figure 5-3.
4. Connect ground lead of Channel A and Channel B to TP11 and TP14 as shown in Figure 5-3.
5. Inject 30-mV (or less) signal across R14 through isolation transformer.
6. Sweep frequency from 1 kHz to 1 MHz, with 1-0Hz or lower post filter.
7. Control loop gain can be measured by Equation 2:
   Equation 2.
8. Control loop phase is measured by the phase difference between Channel A and Channel B.
9. Control to output response (power stage transfer function) can be measured by connecting Channel A probe to TP6 (COMP) and Channel B probe to TP13.
10. Output to control response (error amplifier transfer function) can be measured by connecting Channel B probe to TP6 (COMP) and Channel A probe to TP12.
11. Disconnect isolation transformer from TP12 and TP13 before making other measurements (signal injection into feedback may interfere with accuracy of other measurements).