Texas Instruments SEPIC Evaluation Module for TPS55340 TPS55340EVM-147 TPS55340EVM-147 Scheda Tecnica
Codici prodotto
TPS55340EVM-147
IN
OUT
F
LIM
SW
OUT
F
IN
OUT
OUT
IN
EST
V min
V
+V
I
min-
×
2×f
×L V
+V +V min
I
max=
V
+1
V min×
§
·
¨
¸
©
¹
§
·
¨
¸
©
¹
IN
OUT
V max=38V-V
OUT
V
R1
R2
1
1.229V
æ
ö
=
´
-
ç
÷
è
ø
Modifications
3
Modifications
These evaluation modules provide access to the features of the TPS55340. Some modifications to this
module are possible.
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 10k
Ω. To
change the output voltage of the EVM, change the value of resistor R1. Calculate the value of R1 for a
specific output voltage by using
specific output voltage by using
.
(1)
Note that V
IN
must be in a range so that the on-time is greater than the minimum controllable on-time
(77ns typical), and the maximum duty cycle is less than 89% minimum and 93% typical.
After adjusting the output voltage the maximum input voltage must be taken into consideration. The
voltage on the internal FET, the SW pin, is equal to the sum of the input voltage and the output voltage.
By using
voltage on the internal FET, the SW pin, is equal to the sum of the input voltage and the output voltage.
By using
you can determine the recommended maximum input voltage.
(2)
3.2
Maximum Output Current
After adjusting input or output voltage settings, verify the maximum output current per
below,
where I
LIM
is the peak current limit of the TPS55340 and V
F
is the forward voltage drop of the external
schottky diode (D1). This equation combines Equations 40, 42, and 44 from the datasheet.
(3)
3.3
Slow-Start Time
The slow-start time can be adjusted by changing the value of C3. The EVM uses C3 = 0.047 µF as
recommended on the data sheet to avoid any overshoot during start-up. A larger capacitance increases
the slow-start time while a smaller capacitance decreases it.
recommended on the data sheet to avoid 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.
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 TPS55340EVM-147 evaluation
module. 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.
module. 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.
3
SLVU742A – June 2012 – Revised August 2013
TPS55340EVM-147, 6V to 18V Input, 12V Output SEPIC Evaluation Module
Copyright © 2012–2013, Texas Instruments Incorporated