Texas Instruments TPS55340EVM-017, User Manual, Page: 12 / 22

SW (20.0 V/div)
V
IN
(5.00 V/div)
V
OUT
(10.0 V/div)
Timebase (2.00 ms/div)
Board Layout
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12 SLVU668B – April 2012 – Revised July 2019
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TPS55340EVM-017, 5-V to 12-V Input, 24-V Output Boost Evaluation Module
Figure 16 shows the shutdown waveforms for the EVM. The input voltage ramps down with the input
voltage power supply and EN is tied to V
IN
. When V
IN
is less than the 2.5-V typical UVLO, the converter
stops switching and the output voltage ramps down. The load is 120
Ω
.
Figure 16. TPS55340EVM-017 Power Down With V
IN
5 Board Layout
This section provides a description of the EVM board layout and layer illustrations.
5.1 Layout
The board layout for the EVM is shown in Figure 17 through Figure 21 . The top-side layer of the EVM is
laid out in a manner typical of a user application. The top, bottom, and internal layers are 2-oz. copper.
The top layer contains the main power traces for V
IN
, V
OUT
, and SW. Also on the top layer are connections
for the remaining pins of the TPS55340 and a large area filled with ground. The internal layers and bottom
are primarily ground with additional fill areas for V
IN
and V
OUT
. The top-side ground traces connect to the
bottom and internal ground planes with multiple vias placed around the board. Nine vias directly under the
TPS55340 device provide a thermal path from the top-side ground plane to the bottom-side ground plane.
Place the output decoupling capacitors (C8–C11) as close to the IC as possible. The copper area of the
SW node is kept small minimizing noise. The vias near the diode, D1, on the V
OUT
plane aid with thermal
dissipation. Additionally, keep the voltage setpoint resistor divider components close to the IC. The voltage
divider network ties to the output voltage at the point of regulation, the copper V
OUT
trace at the J7 output
connector. For the TPS55340, an additional input bulk capacitor may be necessary, depending on the
EVM connection to the input supply. Critical analog circuits such as the voltage setpoint divider, frequency
set resistor, slow-start capacitor, and compensation components terminate to ground using a separate
ground trace on the top and bottom connected power ground, pour only at one point directly under the IC.