SLUUCQ1 March 2023 TPS546D24S
To evaluate the efficiency of the power train (device and inductor), make sure to measure the voltages at the correct location. This action is necessary because otherwise the measurements 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 must 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 results in efficiency measurements that excluded losses due to the wires and connectors.
Test Point | Node Name | Description | Comment |
---|---|---|---|
TP12 | PVIN | Input voltage measurement point for VIN+ | The pair of test points are connected to the PVIN/PGND pins of U1_P1. The voltage drop between input terminal to the device pins is included for efficiency measurement. |
TP15 | PGND | Input voltage measurement point for VIN– (GND) | |
TP22 | 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. |
TP25 | GND | Output voltage measurement point for VOUT– (GND) |
For more accurate efficiency measurements of the power train, remove the voltage drop between the power train and the terminals from the measurement. Using the test points in Table 6-2 reduces these losses. To average the voltages at each test point so that only one meter is needed for PVIN and VOUT, add some resistance between the each test point and the meter. For the measurements taken in this user's guide, a 1.5-kΩ resistor was added in series with each test point. Using these test points reduced the measured power loss at 80 A load by approximately 0.5 W. This power is lost in the copper traces of the PCB.
Test Point | Node Name | Description | Comment |
---|---|---|---|
TP1_P1 | PVIN_P1 | Input voltage measurement point for VIN+ | This pair of test points are connected to PVIN and PGND near the pins of U1_P1 |
TP4_P1 | GND_P1 | Input voltage measurement point for VIN– (PGND) | |
TP1_P2 | PVIN_P2 | Input voltage measurement point for VIN+ | This pair of test points are connected to PVIN and PGND near the pins of U1_P2 |
TP4_P2 | GND_P2 | Input voltage measurement point for VIN– (PGND) | |
TP13 | VOUT_P1 | Output voltage measurement point for VOUT+ | This pair of test points are connected to VOUT and GND near the output inductor for U1_P1 |
TP16 | GND_P1 | Output voltage measurement point for VOUT– (GND) | |
TP26 | VOUT_P2 | Output voltage measurement point for VOUT+ | This pair of test points are connected to VOUT and GND near the output inductor for U1_P2 |
TP30 | GND_P2 | Output voltage measurement point for VOUT– (GND) |