11 Layout

11.1 Layout Guidelines

The switching node rise and fall times should be minimized for minimum switching loss. Proper layout of the

components to minimize high frequency current path loop (see Figure 11-1) is important to prevent electrical and

magnetic field radiation and high frequency resonant problems. Follow this specific order carefully to achieve the

proper layout.

• Place input capacitor as close as possible to PMID pin and GND pin and use shortest copper trace

connection or GND plane.

• Put output capacitor near to the inductor output terminal and the charger device. Ground connections need to

be tied to the IC ground with a short copper trace or GND plane

• Place inductor input terminal to SW pin as close as possible and limit SW node copper area to lower

electrical and magnetic field radiation. Do not use multiple layers in parallel for this connection. Minimize

parasitic capacitance from this area to any other trace or plane.

• Route analog ground separately from power ground if possible. Connect analog ground and power ground

together using thermal pad as the single ground connection point under the charger device. It is acceptable to

connect all grounds to a single ground plane if multiple ground planes are not available.

• Decoupling capacitors should be placed next to the device pins and make trace connection as short as

possible.

• It is critical that the exposed thermal pad on the backside of the device be soldered to the PCB ground.

Ensure that there are sufficient thermal vias directly under the IC, connecting to the ground plane on the other

layers

• Ensure that the number and sizes of vias allow enough copper for a given current path

• Try to avoid ground planes in parallel with high frequency traces in other layers.

• See the EVM design for the recommended component placement with trace and via locations.

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Figure 11-1. High Frequency Current Path

11.2 Layout Example

The device pinout and component count are optimized for a 2 layer PCB design. The 2-layer PCB layout

example is shown in Figure 11-2.

BQ25302

SLUSCZ3 – OCTOBER 2020

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