TWR-K60N512-KEIL Freescale Semiconductor, TWR-K60N512-KEIL Datasheet - Page 21

• Manufacturer Part Number: TWR-K60N512-KEIL
• Description: K60N512 Keil Tower Kit
• Manufacturer: Freescale Semiconductor
• Series: Kinetisr
• Type: MCUr

Specifications of TWR-K60N512-KEIL

• Rohs Compliant: YES
• Contents: 4 Boards, Documentation, DVD
• Peak Reflow Compatible (260 C): Yes
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: Freescale Tower System, K60N512

Chapter 2 General System Setup (Hardware Considerations)
In general, the decoupling network series elements are small inductors or ferrite beads
that have a small impedance (about 100 Ω at 100 MHz). The capacitors are generally
10nF to 1uF and do not have to be the same value on both sides of the filter – select a
lower value for the side that has the higher frequency content.
2.3 PCB routing considerations
This section covers critical power and filtering aspects of PCB layout.
2.3.1 Power supply routing
Routing of power and ground to digital systems is a topic that is discussed and debated in
many textbooks and references. The basic concept is to ensure that the MCU and other
digital components have a low impedance path to the power supply. The typical guidance
that was given for one and two layer PCBs was to use wide traces and few layer
transitions. The recommendations for today’s high speed MCUs follow those given for
high speed microprocessor systems – specifically, use planes for power and ground. This
may raise the PCB cost, but the benefits of crosstalk reduction, reduction of RF
emissions, and improved transient immunity can be realized with lower overall
production and maintenance costs.
In general, the ground routing should take precedence over any other routing. Ground
planes or traces should never be broken by signals. For packages with leads, like the
LQFP, a ground plane directly below the MCU package is recommended to reduce RF
emissions and improve transient immunity. All of the VSS pins of the MCU should be
tied to a ground plane. Ground traces (from a plane) should be kept as short as possible as
they are routed to circuitry on signal layers (top and bottom). Power planes may be
broken to supply different voltages. All of the VDD pins of the MCU should be tied to
the proper power plane. Power traces (from the planes) should be kept as short as
possible as they are routed to circuitry (pullups, filters, other logic & drivers) on the top
and bottom layers. More information is given in the PCB Layer Stack-up section below.
2.3.2 Power supply decoupling and filtering
As mentioned in the power domains section, decoupling networks are used to separate
domains. Bypass capacitors, while also called decoupling capacitors, are the storage
elements that provide the instantaneous energy demanded by the high speed digital
circuits.
Kinetis Quick Reference User Guide, Rev. 0, 11/2010
Freescale Semiconductor
21