PRIXP420ABB 885158 Intel, PRIXP420ABB 885158 Datasheet - Page 57

• Manufacturer Part Number: PRIXP420ABB 885158
• Manufacturer: Intel

Specifications of PRIXP420ABB 885158

• Lead Free Status / Rohs Status: Compliant

General PCB Guide—Intel
5.0
5.1
5.2
5.3
5.4
December 2007
Document Number: 252817- 008US
General PCB Guide
PCB Overview
Beginning with components selection, this chapter presents general PCB guidelines. In
cases where it is too difficult to adhere to a guideline, engineering judgment must be
used. The methods are listed below as simple DOs and DON’Ts.
This chapter does not discuss the functional aspects of any bus, or layout guides for
any interfaced devices.
General Recommendations
It is recommended that boards based on the IXP42X product line and IXC1100 control
plane processors employ a PCB stackup yielding a target impedance of 50 Ω ± 10%
with 5 mil nominal trace width; that is, the impedance of the trace when not subjected
to the fields created by changing current in neighboring traces.
When calculating flight times, it is important to consider the minimum and maximum
impedance of a trace based on the switching of neighboring traces. Using wider spaces
between the traces can minimize this trace-to-trace coupling. In addition, these wider
spaces reduce cross-talk and settling time.
Component Selection
Component Placement
Place ALL high-frequency components in the middle; medium-frequency around the
high-frequency components; and the low-frequency components around the edge of
the printed circuit board, as shown in
• Do not use components faster than necessary
• Use components with output drive strength (slew-rate) controllable if available
• Use SMT components (not through-hole components) as through-hole (leaded)
• Avoid sockets when possible
• Minimize number of connectors
components have more stub inductance due to the protruding leads.
— Clock rise (fall) time should be as slow as possible, as the spectral content of
®
the waveform decreases
IXP42X product line and IXC1100 control plane processors
Intel
®
IXP42X Product Line of Network Processors and IXC1100 Control Plane Processor
“Component Placement on a PCB” on page
Hardware Design Guidelines
58.
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