Datasheet

Board Layout

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3 Board Layout

This section provides a description of the TPS56921EVM-188 board layout and layer illustrations.

3.1 Layout

The board layout for the TPS56921EVM-188 is shown in Figure 13 through Figure 17. 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 PVIN, VIN, V

OUT

, and VPHASE. Also on the top layer are

connections for the remaining pins of the TPS56921 and a large area filled with ground. The internal layer-

1 is dedicated to a power ground plane. the internal layer-2 contains an analog ground fill area. This

analog ground is used as a return for the I

C interface as well as for sensitive analog circuits for RT, SS,

EN, COMP and VSENSE. The analog ground is connected to the main power ground at one place to

inhibit circulating currents. This connection is made at the via near TP7. Internal layer-2 also contains

additional fill areas for PVIN and V

OUT

, as well as connections to the I

C interface connector at J3. The

bottom layer contains a power ground plane only. The top-side ground traces are connected to the bottom

and internal ground planes with multiple vias placed around the board including nine vias directly under

the TPS56921 and 12 vias directly adjacent to the TPS56921device to provide a thermal path from the

top-side ground area to the internal layer-1 and bottom-side ground planes.

The input decoupling capacitors (C1,C2, C3 and C4) and bootstrap capacitor (C8) are all located as close

to the IC as possible. Additionally, the voltage setpoint resistor divider components are kept 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 J4 output connector. For the TPS56921, an additional input bulk capacitor may be required,

depending on the EVM connection to the input supply.

Figure 13. TPS56921EVM-188 Top-Side Assembly Figure 14. TPS56921EVM-188 Top-Side Layout

TPS56921EVM-188, 9-A, SWIFT™ Regulator Evaluation Module SLVU793–October 2012

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