Intel 855GME User Manual

74
Intel
®
855GME Chipset and Intel
®
6300ESB ICH Embedded Platform Design Guide
4.1.11 Pentium
®
M/Celeron
®
M Processor V
CCSENSE
/V
SSSENSE
Design Recommendations
The VCCSENSE and VSSSENSE signals of the Intel Pentium M/Celeron M processor provide
isolated, low impedance connections to the processor’s core power (VCC) and ground (VSS).
These pins may be used to sense or measure power (VCC) or ground (VSS) near the silicon with
little noise. To make them available for measurement purposes, it is recommended that
VCCSENSE and VSSSENSE both be routed with a Zo = 55
Ω ± 15 percent trace of equal length.
Use 3:1 spacing between the routing for the two signals and all other signals shall be a minimum of
25 mils (preferably 50 mils) from VCCSENSE and VSSSENSE routing. Terminate each line with
an optional (default is No Stuff) 54.9
Ω ± 1 percent resistor. Also, a ground via spaced 100 mils
away from each of the test point vias for VCCSENSE and VSSSENSE shall be added. A third
ground via shall also be placed in between them to allow for a differential probe ground. Refer to
Figure 35 for the recommended layout example.
4.1.12 PLL Voltage Design for Low Voltage Intel
®
Pentium
®
M
Processors on 90 nm process with 2 MB L2 Cache
One primary difference between the Intel Pentium M processor (130nm) and the Low Voltage
Intel
®
Pentium
®
M Processor on 90 nm process with 2 MB L2 cache or the Intel
®
Celeron
®
M
Processor on 90nm process is the analog PLL voltage supplying the processor’s on-die clock
generators. The VCCA PLL power delivery pins of the Low Voltage Intel Pentium M Processors
on 90 nm process with 2 MB L2 cache and the Intel
®
Celeron
®
M Processor on 90nm process have
the option of using either a 1.8 V or 1.5 V power supply. For a platform supporting only Low
Voltage Intel Pentium M Processors on 90 nm process with 2 MB L2 cache or Intel
®
Celeron
®
M
Processor on 90nm process, the VCCA[3:0] pin should be powered by the 1.5 V rail, since the 1.5
V rail is already required for GMCH. This eliminates the need for a 1.8 V rail on the platform.
However, if a platform is to also support Intel Pentium M processors (130nm) and standard voltage
Intel
®
Pentium
®
M Processors on 90 nm process with 2 MB L2 cache, then the 1.8 V rail must be
used for the analog PLL voltage supply.
Figure 35. V
CCSENSE
/V
SSSENSE
Routing Example
VCCSENSE
GND
54.9
Ω
54.9
Ω
VSSSENSE
100 mil

Intel 855GME Specifications

General

Brand	Intel
Model	855GME
Category	Computer Hardware
Language	English