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July 17, 2002
112
PCB Layout Guidelines
•
When transitioning signals between the return paths, insert a ground via next to the signal via, i.e. when
transitioning from Signal 1 or Signal 2 to Signal 3, or when transitioning from Signal 3 or Signal 4 to
Signal 1. This will maintain return path continuity.
•
For improved manufacturing of the PCB, 0.006” traces and 0.006” spaces is recommend for the outer
two layers (top and bottom), with 0.005” traces and 0.005” spaces on the internal layers.
•
DO NOT match impedances on traces wider than 0.006”.
•
DO NOT allow cutouts in the ground planes.
7.2 Example PCB Fabrication Notes
•
The finished printed circuit board shall meet the requirements of IPC-A-600.
•
Configuration of the printed circuit board not specifically dimensioned on the drawing shall be controlled
by the Gerber data.
•
Material: 0.056” ± 0.006” thick glass epoxy, natural color. Laminated NEMA grade FR4. See layer stack-
up for copper weight and layer orientation. Core and prepreg combinations are optional to the
manufacturer unless otherwise specified in the layer stack-up.
•
Plating: all holes and conductive surfaces shall be plated with 0.001” copper minimum. All copper areas
not covered by solder mask shall be solder coated 0.0003” minimum.
•
All hole diameters are stated as finished hole sizes.
•
Solder mask: photo-imaged liquid polymer on both sides of board in accordance with IPC-SM-840, type
B Class 2 over bare copper.
•
Component marking: silk-screen component side (and solder side) white, non-conductive epoxy ink.
Lands and exposed plated areas to be free of ink.
•
Bow and twist: shall not exceed 0.005” per lineal inch.
•
Electrical test: the printed wiring board shall be electrically tested for opens and shorts. The results of the
electrical test shall be documented and delivered along with each lot.
•
Identification: vendor logo to be etched on the solder side, silk-screen date code on the bottom side.
•
Characteristic impedance: 55
Ω
± 10%. Note: this will be 60
Ω
± 10% when DDR SDRAM is used in the
design.
Summary of Contents for Crusoe TM5500
Page 1: ...TM5500 TM5800 System Design Guide July 17 2002...
Page 6: ...July 17 2002 6 List of Tables...
Page 8: ...July 17 2002 8 List of Figures...
Page 50: ...July 17 2002 50 Processor Power Supplies and Power Management...
Page 110: ...July 17 2002 110 System Design Considerations...
Page 122: ...July 17 2002 122 System Design Checklists...
Page 128: ...July 17 2002 128 Serial Write protection PLD Data...
Page 130: ...July 17 2002 130 Index...