AN11524
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© NXP Semiconductors N.V. 2015. All rights reserved.
Application note
Rev. 1 — 17 February 2015
33 of 54
NXP Semiconductors
AN11524
NXQ1TXA6 Evaluation Board
8. PCB layout guidelines
Having a proper printed circuit board (PCB) layout is critical to the success of the
application. A poor constructed PCB layout can cause the whole application not to
function properly. Beyond basic circuit operation, it can also directly influence the
ElectroMagnetic Compatibility (EMC) profile. Therefore, it is imperative that care
should be exercised during the PCB layout stage.
Several good PCB design tips are explained here.
8.1 Ground planes
Design with a 4-layer PCB. The layer stack-up applied in NXQ1TXA6 Evaluation Board is
as follows:
1. Layer 1: Component placement and signal trace
2. Layer 2: Clean uninterrupted ground
3. Layer 3: Signal trace
4. Layer 4: Ground and minimal routing trace if required
Notice that with this stacking technique, the signal traces are sandwiched between
grounds. It provides a solid ground reference plane and helps to minimize
ElectroMagnetic Interference (EMI) noise emissions.
As a rule, use ground planes: use copper-pour in unused areas of the PCB and stitch
these areas with vias to inner ground planes.
8.2 NXQ1TXA6 charging controller
The center pad (pin 33) under NXQ1TXA6 charging controller is a ground pin. It is
important to stitch with vias to inner ground planes to provide a solid ground reference.
Make sure the decoupling capacitors C101and C102 on VDD1 supply pin 6 and VDD2 pin
26, are close by and connected with a wide trace. It ensures effective decoupling action to
ground.