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Test Procedure
13
SLUUBN2 – March 2017
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Copyright © 2017, Texas Instruments Incorporated
TPS549B22EVM-847, 25-A Single Synchronous Step-Down Converter With
Full Differential Sense and PMBus™
10
Test Procedure
10.1 Line and Load Regulation Measurement Procedure
Use the following procedures for line and load regulation measurement.
1. Connect VOUT to J3 and VOUT_GND to J5
Figure 2
.
2. Ensure that the electronic load is set to draw 0 A
DC
.
3. Connect VIN to J1 and VIN_GND to J2
Figure 2
.
4. Connect the USB interface adapter as shown in
Figure 4
.
5. Increase V
IN
from 0 V to 12 V using the digital multimeter to measure input voltage.
6. Launch the Fusion GUI software. See the screen shots in
Section 12
for more information.
7. Configure the EVM operating parameters as desired.
8. Use the other digital multimeter or the oscilloscope to measure output voltage V
OUT
at TP2 and TP10
as you vary the external voltage source.
Table 4. List of Test Points for Line and Load Measurements
Test Point
Node Name
Description
TP2
LocS+
Sense VOUT + locally across C5. Use for efficiency and ripple measurements
TP10
LocS–
Sense VOUT - locally across C5. Use for efficiency and ripple measurements
TP4
PVIN
Sense VIN + across C10
TP13
PGND
Sense VIN - across C10
9. Vary the load from 0 A
DC
to maximum rated output 25 A
DC
. V
OUT
must remain in regulation as defined in
Table 1
.
10. Vary V
IN
from 5 V to 14 V. V
OUT
must remain in regulation as defined in
Table 1
.
11. Decrease the load to 0 A.
12. Decrease V
IN
to 0 V or turn off the supply.
10.2 Efficiency
To measure the efficiency of the power train on the EVM, it is important to measure the voltages at the
correct location. This is necessary because otherwise the measurements will include losses in efficiency
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, and they must not be
included in efficiency measurements.
Table 5. List of Test Points for Efficiency Measurements
Test Point
Node Name
Description
TP2
LocS+
Sense VOUT + locally across C25. Use for efficiency and ripple measurements
TP10
LocS-
Sense VOUT - locally across C25. Use for efficiency and ripple measurements
TP4
PVIN
Sense VIN + across C10
TP13
PGND
Sense VIN - across C10
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. Using these measurement points result in
efficiency measurements that do not include losses due to the connectors and PCB traces.
10.3 Equipment Shutdown
1. Reduce the load current to 0 A.
2. Reduce input voltage to 0 V.
3. Shut down the external fan if in use.
4. Shut down equipment.
