Texas Instruments TPSM8D6C24, User Manual

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6.2 Efficiency Measurement Test Points
To evaluate the efficiency of the power train (device and inductor), it is important to measure the voltages at
the correct location. This is necessary because otherwise the measurements will include losses that are not
related to the power train itself. Losses incurred by the voltage drop in the copper traces and in the input and
output connectors are not related to the efficiency of the power train, which should not be included in efficiency
measurements.
Input current can be measured at any point in the input wires, and output current can be measured anywhere in
the output wires of the output being measured.
Table 6-1 shows the measurement points for input voltage and output voltage. VIN and VOUT are measured
to calculate the efficiency. Using these measurement points will result in efficiency measurements that excluded
losses due to the wires and connectors.
Table 6-1. Test Points for Efficiency Measurements
Test Point Node Name Description Comment
TP1 PVIN
Input voltage measurement point
for VIN+
The pair of test points are connected to the PVIN/PGND pins of U1. The voltage drop between
input terminal to the device pins is included for efficiency measurement.
TP3 PGND
Input voltage measurement point
for VIN– (GND)
TP6 VOUT
Output voltage measurement
point for VOUT+
The pair of test points are connected near the output terminals. The voltage drop from the
output point of the inductor to the output terminals is included for efficiency measurement.
TP10 PGND
Output voltage measurement
point for VOUT– (GND)
6.3 Control Loop Gain and Phase Measurement Procedure
The TPSM8D6C24EVM-2PH includes a 49.9-Ω series resistor in the feedback loop for V
OUT
. The resistor is
accessible at the test points TP7 and TP8 for loop response analysis. These test points should be used during
loop response measurements as the perturbation injecting points for the loop. See the description in
Table 6-2 .
Table 6-2. List of Test Points for Loop Response Measurements
Test Point Node Name Description Comment
TP7 CHA_Vout Input to feedback divider of VOUT The amplitude of the perturbation at this node should be limited to less than 30 mV
TP8 CHB_Vout Resulting output of VOUT Bode can be measured by a network analyzer with a CH_B/CH_A configuration
Measure the loop response with the following procedure:
1. Set up the EVM as described in Section 4.2 .
2. Connect the isolation transformer of the network analyzer from TP7 to TP8.
3. Connect the input signal measurement probe to TP7. Connect the output signal measurement probe to TP8.
4. Connect the ground leads of both probe channels to TP3.
5. On the network analyzer, measure the Bode as TP8/TP7 (Out/In).
www.ti.com Test Procedure
SLUUCL8A – DECEMBER 2021 – REVISED FEBRUARY 2022
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TPSM8D6C24 2-Phase Power Module Evaluation Module User's Guide 9
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