Texas Instruments PWR054-001, User Manual

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Software Setup and Operation
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Resistor R16 is present to observe the load step current by measuring the voltage across TP1 and TP2.
Oscilloscope settings of 100 mV / div translate to a current in R16 of 1 A / div. R19 and R20 might be
installed if large load current steps at low output voltages are desired.
3.2 Measuring the Control Loop
A bode plot of each output can be easily taken with a small modification to the EVM. To measure the
control loop response of DCDC_A, for example, R1 is replaced with a 10-
Ω resistor. Then, the injection
signal is applied and the loop response measured across this resistor. Figure 14 shows the results of this
test.
3.3 Circuit Modifications
Modifications may be made to the circuit. Any modifications will affect the performance of the EVM and
must remain within the limits of the TPS650380 IC, as detailed in the data sheet.
CAUTION
As shipped, the EVM is configured for local sensing of the output voltages. If
remote sensing at the loads is desired, modification of the EVM is required as
described in the
Remote Sense Resistors section.
3.3.1 Output Capacitors
There are locations for extra output capacitors to be installed on each output voltage in order to reduce
output ripple or lessen the voltage drop due to a load transient. Some capacitors are located near the
TPS650380 IC, while others can be installed closer to the point of load, which is simulated by the load
step circuit. The total output capacitance on each output must remain below the maximum capacitance
allowed in the data sheet.
3.3.2 Remote Sense Resistors
R1, R2, R3, R4, and R9 come populated with 0- Ω resistors that provide local output voltage sensing. Each
output voltage is regulated at the output connector on the EVM. If it is desired to regulate the output
voltage at the load, these resistors should be removed and wires used to connect the J5, J8, and J10
headers to each load. These wires should be twisted and kept as short as possible to minimize noise
pickup. Use of the EVM without the local sense resistors or remote sense wires installed may damage the
load or EVM.
3.3.3 I
2
C Pull-up Resistors
R5, R6, R7, and R8 are locations for optional pull-up resistors for the I
2
C signals. They are required when
not using the USB-TO-GPIO adaptor but are not recommended when using the adaptor. If used, their
typical value is around 2.2 k
Ω .
10 TPS650380EVM-054 SLVU720A – June 2012 – Revised November 2012
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