Texas Instruments TPS55340EVM-017, Руководство пользователя, Страница: 3 / 22

OUT
V
R1 R2 1
1.229 V
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Modifications
3 SLVU668B – April 2012 – Revised July 2019
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TPS55340EVM-017, 5-V to 12-V Input, 24-V Output Boost Evaluation Module
3 Modifications
These evaluation modules provide access to the features of the TPS55340. Some modifications to this
module are possible.
3.1 Output Voltage Set Point
The resistor divider network of R1 and R2 sets the output voltage. Keep R2 fixed at or close to 10 k
Ω
.
Change the output voltage of the EVM by changing the value of resistor R1. Calculate the value of R1 for
a specific output voltage by using
Equation 1 .
(1)
Note that V
IN
must be in a range so that the on-time is greater than the minimum controllable on-time (77
ns typical), and the maximum duty cycle is less than 89% minimum and 93% typical.
3.2 Maximum Output Current
After adjusting input or output voltage settings, verify the maximum output current pursuant to the
equations given on the data sheet.
3.3 Slow-Start Time
Adjust the slow-start time by changing the value of C3. The EVM uses C3 = 0.047 µF, as recommended
on the data sheet, avoiding any overshoot during start-up. A larger capacitance increases the slow-start
time while a smaller capacitance decreases it.
3.4 Other Modifications
Please see data sheet recommendations and equations when changing the switching frequency,
input/output voltage range, input inductor, output capacitors or compensation.
4 Test Setup and Results
This section describes how to properly connect, set up, and use the EVM. Included are test results typical
for the evaluation module covering efficiency, output voltage regulation, load transients, loop response,
output ripple, input ripple, start-up and shut-down.
4.1 Input/Output Connections
The EVM is provided with input and output connectors and test points as shown in Table 3 . Connect a
power supply capable of supplying 5 A to J6 through a pair of 20 AWG wires. The jumper across JP1 in
the ON position (1-2) must be in place. Connect the load to J7 through a pair of 20 AWG wires. The
maximum load-current capability must be at least 1.9 A. Minimize wire lengths to reduce losses in the
wires. Header J1 provides a place to monitor the V
IN
input voltages with J3 providing a convenient ground
reference. Use J2 to monitor the output voltage with J4 as the ground reference.
Table 3. EVM Connectors and Test Points
Reference Designator Function
J1 2-pin header for V
IN
input voltage connections
J2 2-pin header for V
OUT
input voltage connections
J3, J4 2-pin header for GND connections
J5 2-pin header for synchronizing signal and ground
J6 V
IN
input voltage connector. (See Table 1 for V
IN
range.)
JP1 3-pin header for enable. Jumper installed from pins 1-2 enables and from pins 2-3 disables.
TP1 SW test point
TP2 Test point between voltage divider network and output. Used for loop-response measurements.