User's Manual

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User Manual 2012/06/28
10. LAYOUT RECOMMENDATIONS ON CUSTOMER BOARD
10.1 GENERAL RECOMMENDATIONS ON LAYOUT
There are many different types of signals in the module which may be interfered each other. Particularly, Audio
signals are very sensitive to external signals such as VBAT... Therefore it is very important to follow some rules
to avoid signal disruption or abnormal behaviour.
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Magnetic fields generated by VBAT tracks may cause speaker interference and burst noise. In this case,
modify layout of the VBAT tracks to reduce the phenomenon.
10.1.1 Ground
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Ensure the ground plane is as complete as possible
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Grounding of components should be connected to the ground layer through a number of irregularly
distributed vias.
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Top and bottom layer should set aside as much space for the ground plane as possible. Flood remaining
empty surfaces of the layout of those two layers with a ground plane connected to the main ground through as
many vias as possible.
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Proper grounding is crucial to end-product performance. At least one layer must be a dedicated ground
plane. This ground plane is the common point referenced by all end-product circuits.
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In addition to the dedicated ground plane layer, unused space on all PCB layers should be filled with
grounding to provide the most robust grounding possible from layer to layer.
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Bypass capacitors should be connected directly to their surface layer ground fill. Multiple vias should
connect each capacitor directly to the main ground plane, with one via in the capacitor’s pad plus several vias
within the surface layer ground fill area.
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Digital ground should connect directly to the main ground plane. In addition, each layer between layer 1
and the main ground should include ground fills directly below the center grid area’s digital pins, with each stack
of vias connecting to each ground fill area. The large mass of copper tied together using this technique provides
optimal electrical grounding and thermal conductivity.
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The analog/RF ground pins are connected to each other, but isolated from the digital ground (until main
ground). Like the digital pins, the analog/RF pins should connect directly to the main ground plane. In addition,
each layer between layer 1 and the main ground should include ground fills directly below the outer layer’s
analog/RF pins, with each stack of vias connecting to each ground fill area. The large mass of copper tied
together using this technique provides optimal electrical grounding and thermal conductivity.
10.1.2 Power supplies
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A layer for power supply signals (VBAT, VGPIO,SIM_VCC_VCC) is recommended.
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Looping of power signal layouts must be avoided in device design.
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Ensure suitable power supply (VBAT, VGPIO,SIM_VCC) track width and thickness.