Mobile Intel Pentium 4 Processor - M and Intel 845MP/MZ Chipset Platform Design Guide

Mobile Intel

Pentium

4 Processor-M and Intel

845MP/845MZ Chipset Platform

Design Guide 47

4.6.3. High Frequency Decoupling

System motherboards should include high frequency decoupling capacitors as close to the socket power

and ground pins as possible. A total of thirty-eight 10.0-

µF, X5R/X7R, 1206 package, ceramic

capacitors are recommended to provided high frequency decoupling for the processor. Ten of these 1206

capacitors should be placed in the socket cavity area. Fourteen of these 1206 capacitors should be

placed on the north side of the cavity and fourteen of these 1206 capacitors should be placed on the south

side of the cavity. See Figure 19 for an example on placement of the high frequency decoupling

capacitors.

Figure 19. Processor High Frequency Decoupling Placement Example

VCC

VSS

4.6.4. Bulk Decoupling

System motherboards should include bulk-decoupling capacitors as close to the processor socket power

and ground pins as possible (<1.0 inch). The maximum Equivalent Series Resistance (ESR) should be

equal to or less than 2.5 m

Ω.

4.7. Thermal Power Dissipation

Power dissipation has traditionally been a thermal/mechanical challenge for mobile system designers.

The amount of current required from the processor power delivery circuit and the heat generated by

processors has increased as processor frequencies go up and the silicon process geometry shrinks. The

package of any integrated device can only dissipate so much heat into the surrounding environment. The

temperature of a device, such as a processor power delivery circuit-switching transistor, is a balance of