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PCB Layout Guideline

4 PCB Layout Guideline

1. As with all switching power supplies, the layout is an important step in the design, especially at high

peak currents and high switching frequencies. If the layout is not carefully done, the boost

converter/charger could show stability problems as well as EMI problems. Therefore, use wide and

short traces for the main current path and for the power ground paths. The input and output capacitor,

as well as the inductor should be placed as close as possible to the IC.

2. The resistors that program the thresholds should be placed as close as possible to the input pins of the

IC to minimize parasitic capacitance to less than 2pF.

3. To lay out the ground, it is recommended to use short traces as well, separated from the power ground

traces. This avoids ground shift problems, which can occur due to superimposition of power ground

current and control ground current. Assure that the ground traces are connected close to the device

GND pins.

4. It is critical that the exposed thermal pad on the backside of the bq25504 package be soldered to the

PCB ground. Make sure there are sufficient thermal vias right underneath the IC, connecting to the

ground plane on the other layers.

5. Decoupling capacitors for VSTOR, VBAT should make the interconnections to the any Load as short

as possible.

6. EVM layout can be used as guidance though a smaller layout is achievable.

SLUU654A–October 2011–Revised October 2011 bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for

Energy Harvester Applications

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