Electrical Specifications
2 Electrical Specifications
This chapter describes the electrical characteristics of the processor interfaces and
signals. DC and AC electrical characteristics are provided.
2.1
Power and Ground Lands
The processor has VCC (power), VTT and VSS (ground) inputs for on-chip power
distribution. All power lands must be connected to VCC, while all VSS lands must be
connected to a system ground plane. The processor VCC lands must be supplied the
voltage determined by the Voltage IDentification (VID) lands.
The signals denoted as VTT provide termination for the front side bus and power to the
I/O buffers. A separate supply must be implemented for these lands, that meets the
VTT specifications outlined in Table 2-4.
2.2
Decoupling Guidelines
Due to its large number of transistors and high internal clock speeds, the processor is
capable of generating large current swings. This may cause voltages on power planes
to sag below their minimum specified values if bulk decoupling is not adequate. Larger
bulk storage (CBULK), such as electrolytic or aluminum-polymer capacitors, supply
current during longer lasting changes in current demand by the component, such as
coming out of an idle condition. Similarly, they act as a storage well for current when
entering an idle condition from a running condition. The motherboard must be designed
to ensure that the voltage provided to the processor remains within the specifications
listed in Table 2-4. Failure to do so can result in timing violations or reduced lifetime of
the component.
2.2.1
2.2.2
V
Decoupling
CC
VCC regulator solutions need to provide sufficient decoupling capacitance to satisfy the
processor voltage specifications. This includes bulk capacitance with low effective series
resistance (ESR) to keep the voltage rail within specifications during large swings in
load current. In addition, ceramic decoupling capacitors are required to filter high
frequency content generated by the front side bus and processor activity. Consult the
Voltage Regulator-Down (VRD) 11.0 Processor Power Delivery Design Guidelines For
Desktop LGA775 Socket.
VTT Decoupling
Decoupling must be provided on the motherboard. Decoupling solutions must be sized
to meet the expected load. To insure compliance with the specifications, various factors
associated with the power delivery solution must be considered including regulator
type, power plane and trace sizing, and component placement. A conservative
decoupling solution would consist of a combination of low ESR bulk capacitors and high
frequency ceramic capacitors.
Dual-Core Intel® Xeon® Processor 3000 Series Datasheet
15
INTEL [ INTEL ]
