Datasheet

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Schematic, Bill of Materials, and Board Layout

3.2 Bill of Materials

Table 3. HPA355A Bill of Materials

Count RefDes Value Description Size Part Number MFR

1 C1 10 mF Capacitor, Ceramic, 10V, X7R or X5R, 10% 0805 GRM21BR71A106KE51 Murata

2 C2, C3 10 mF Capacitor, Ceramic, 25V, X7R, 20% 1210 TMK325BJ106MN Taiyo Yuden

1 C4 1 mF Capacitor, Ceramic, 10V, X7R, 10% 0805 GRM21BR71A105KA01 Murata

1 C5 3.3 nF Capacitor, Ceramic, 10V, X7R, 10% 0805 Std Std

1 C6 33 nF Capacitor, Ceramic, 10V, X7R, 20% 0805 Std Std

0 C7 open Capacitor, Ceramic, 10V, X7R, 20% 0805 Std Std

1 D1 PMEG2010AEH Diode, Schottky, 20V, 1A SOD123 PMEG2010AEH Vishay

1 L1 3.3 mH Inductor, 3.3A, 30 mΩ 0.276 x 02.87 inch 7447789003 Wurth Elektronik

1 R1 2040k (232k) Resistor, Chip, 1/10W, 1% 0805 Std Std

1 R2 27k (267k) Resistor, Chip, 1/10W, 1% 0805 Std Std

1 R3 13k Resistor, Chip, 1/10W, 1% 0805 Std Std

1 U1 TPS61085PW IC, 600kHz/1.2MHz Step-Up DC-DC Converter TSSOP-8 TPS61085PW TI

3.3 Board Layout

This section provides the TPS61085EVM board layout and illustrations.

3.3.1 Layout

Board layout is critical for all switch-mode power supplies. Figure 2, Figure 3, and Figure 4 show the

board layout for the HPA355 PCB. The switching nodes with high-frequency noise are isolated from the

noise-sensitive feedback circuitry, and careful attention has been given to the routing of high-frequency

current loops. See the data sheet for further layout guidelines.

The empty pads, located to the right of the inductor, allow for easier measurement of the inductor current

using a current probe. Desolder the inductor, rotate it by 90° and solder it to the additional pads. Then use

a wire from the top pad to the input pad to close the current path again.

SLVU265A–August 2008–Revised October 2010 TPS61085EVM

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