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Marvell PXA27x Processor Family

PXA27x Design Guide - Marvell

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<strong>PXA27x</strong> <strong>Processor</strong> <strong>Family</strong><br />

Design Guide<br />

2.2.1 PCB Layer Assignment (Stackup)<br />

See Figure 2 for illustration of the recommended PCB stackup dimensions and materials. The illustration shows<br />

the recommended PCB layer assignment for an eight-layer PCB using two power and two ground planes. This<br />

configuration provides a continuous VCC_CORE power plane and a divided I/O power plane for the memory and<br />

peripheral domains. See Figure 3 for recommended PCB layer assignment for an eight-layer PCB. See Figure 4<br />

for illustration of the recommended layout of the divided I/O power plane.<br />

Figure 2:<br />

1+6+1 uvia PCB Stackup<br />

External Sig. Layers<br />

1 and 8 50% Copper<br />

¼ oz (9um) + plating<br />

.102mm (4 mil)<br />

μvia copper<br />

plated<br />

Resin Coated Copper<br />

0.070mm<br />

2.8 mils<br />

Internal Layers<br />

2 thru 7 Copper<br />

Pours 70%<br />

Copper<br />

½ oz (18um)<br />

0.13 mm (5.12 mils) FR4<br />

0.13 mm (5.12 mils) FR4<br />

0.13 mm (5.12 mils) FR4<br />

0.13 mm (5.12 mils) FR4<br />

.8-1.0mm<br />

(35 +/-3) mils<br />

0.13 mm (5.12 mils) FR4<br />

0.070mm 2.8 mils<br />

Resin Coated Copper<br />

For the uvia in pad, design the uvia using RCC (resin-coated copper) surface mount capture pads.<br />

Follow the recommendations for meshing:<br />

• For internal layers: 70% cu = 50 mil (1.27mm) pitch with 14.6 mil (.37mm) trace width.<br />

• For external layers: 50% cu = 50 mil (1.27mm) pitch with 22.6 mil (.57mm) trace width.<br />

Follow the recommendations for surface finish and requirements for physical testing:<br />

• Surface Finish OSP<br />

– Use Organic Solder Preservatives (OSP) Entek 106A.<br />

– Ensure that land pads are as flat as possible (no HASL).<br />

– Be aware that industry-wide problems with black pad on ENIG (electroless Ni, Immersion Au) render<br />

results useless.<br />

• Physical testing of PCBs<br />

– Moving point probe damages pads that affect mechanical testing results. Therefore, do not perform<br />

physical tests of PCBs.<br />

Doc. No. MV-S301207-00 Rev. A<br />

Page 26<br />

Copyright © 2009 <strong>Marvell</strong><br />

April 6, 2009, Released

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