Texas Instruments TPS40195, User Manual, Page: 9 / 23

6.3 Loop Analysis (TP7, TP8, TP10)
The TPS40195EVM contains a 1.30-kΩ series resistor in the feedback loop to allow for matched impedance
signal injection into the feedback for loop response analysis.
1. Set up the EVM as described in Section 5.2 and Figure 5-1 .
2. Connect a input signal amplitude measurement probe (Channel A) to TP7 as shown in Figure 6-2 .
3. Connect a output signal amplitude measurement probe (Channel B) to TP8 as shown in Figure 6-2 .
4. Connect the ground lead of Channel A and Channel B to TP10 as shown in Figure 6-2 .
5. Inject 30-mV or less signal across R11 (TP7 and TP8) through an isolation transformer.
6. Sweep frequency from 100 Hz to 1 MHz with 10 Hz or lower post filter.
7. Control loop gain can be measured by 20 × Log (ChannelB/ChannelA).
8. Control loop phase is measured by the phase difference between Channel A and Channel B.
9. Disconnect Isolation transformer from TP7 and TP8 before making other measurements (signal injection into
feedback may interfere with accuracy of other measurements).
10. See Section 6.6 for equipment shutdown.
See Section 7.5 for typical bode plots and transient performance of this EVM.
3.3V
0 to 20A
LOAD1
+
-
V2
+
-
V1
+
-
0 to 20V
V
IN
-
+
A1
Network
Analyzer
CHA CHB
FAN
Figure 6-2. Control Loop Measurement Setup
www.ti.com Test Procedure
SLUU297B – DECEMBER 2007 – REVISED JANUARY 2022
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TPS40195 Buck Controller Evaluation Module User's Guide 9
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