5. Decrease V
IN
to 0 Vdc.
6. Decrease LOAD1 to 0 A.
7. Decrease LOAD2 to 0 A.
4.4 Output Ripple Voltage Measurement Procedure
See
for more information on measuring output ripple.
1. Increase V
IN
from 0 Vdc to 12 Vdc.
2. Adjust LOAD1 to desired load between 0 Adc and 1.5 Adc.
3. Adjust LOAD2 to desired load between 0 Adc and 2.5 Adc.
4. Adjust V
IN
to desired load between 9.6 Vdc and 13.2 Vdc.
5. Connect an oscilloscope probe to TP3 and TP4 or TP18 and TP19 as shown in
6. Measure output ripple.
7. Decrease V
IN
to 0 Vdc.
8. Decrease LOAD1 to 0 A.
9. Decrease LOAD2 to 0 A.
4.5 Control Loop Gain and Phase Measurement Procedure
1. Connect a 1-kHz to 1-MHz isolation transformer to TP6 and TP8 as shown in
2. Connect the input signal amplitude measurement probe (Channel A) to TP8 as shown in
3. Connect output signal amplitude measurement probe (Channel B) to TP6 as shown in
4. Connect ground lead of Channel A and Channel B to TP5 and TP7 as shown in
.
5. Inject 30-mV or less signal across R1 through an 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
C hannelB
20
LOG
ChannelA
æ
ö
´
ç
÷
è
ø
.
8. The control loop phase is measured by the phase difference between Channel A and Channel B.
9. The control loop for Channel 2 can be measured by making the following substitutions:
a. Change TP6 to TP16.
b. Change TP8 to TP14.
c. Change TP5 to TP17.
d. Change TP7 to TP15.
10. Disconnect the isolation transformer before making any other measurements (signal injection into feedback
can interfere with the accuracy of other measurements).
4.6 Equipment Shutdown
1. Shut down the oscilloscope.
2. Shut down V
IN
.
3. Shut down LOAD1.
4. Shut down LOAD2.
5. Shut down the fan.
Test Setup
10
TPS54291 Step-Down Converter Evaluation Module User's Guide
SLVU356A – JANUARY 2010 – REVISED OCTOBER 2021
Copyright © 2021 Texas Instruments Incorporated
