Table 88. Absolute Vs. Relative Voltage Specification; Table 89. Ddr-Sdram So-Dimm Voltage And Current Requirements - Intel 852GME Design Manual

R
percentages should be used where stated. If not stated, then either way is fine. Voltage specs are defined
as either "Absolute" or "Relative." These are described in Table 88.
Note: VREF to SO_DIMM and GMCH should stay on during S3 state on all 852 chipset families.

Table 88. Absolute vs. Relative Voltage Specification

Type of Specification
Absolute Specification
Relative Specification
In the following three tables, only the 2.5-V supply is a fixed, absolute specification, whereas all of the
1.25-V nominal supplies are relative to the 2.5-V supply directly or another 1.25-V supply, which is
then relative to the 2.5-V supply. Due to these 1.25-V relative specifications, it is important that the
1.25-V supply can track the variations in the 2.5-V supply and respond according to the 2.5-V
variations. This can be implemented as shown in the block diagram in Figure 102 where the 2.5-V
output is divided in half and used to generate the 1.25-V reference into the 1.25-V, VR controller
design. In this manner, the 1.25-V VR will respond proportionally to variations in the 2.5-V supply,
improving the voltage margin of the relative supply requirements and overall memory system stability.
As of publication of this document, all specifications were current. However, it is realized that the
current specifications are considered to be higher than actually expected and will be reduced in future
specifications.

Table 89. DDR-SDRAM SO-DIMM Voltage and Current Requirements

Parameter
Core Supply
Voltage, Static
I/O Supply
Voltage, Static
Core Supply
Current, Static
I/O Supply
Current, Static
Absolute I/O
Reference Supply
Voltage, Static
I/O Reference
Supply Current,
Static
® ®
Intel 852GME, Intel 852GMV and Intel
This is a standard specification most commonly used. This means that
the voltage limits are based on a fixed nominal voltage and have a
symmetric ± tolerance added to determine the acceptable voltage
range. For example, a VDD spec does not depend on any other
voltage levels. It is simply 2.5 V ± 8%.
This is a specification whose nominal value is not fixed but is relative
to or is a function of another voltage. This means that the other
voltage must be measured to know what the nominal value is and
then the symmetrical ± tolerance added to that measured value. For
example, a VREF spec depends on the actual value of VDD to
determine VDD/2 and then tolerance ± 0.050 V from this calculated
value.
Symbol Unit
Vdd Volts, V
VddQ Volts, V
Idd Amperes, A
IddQ Amperes, A
VREF Volts, V
Iref Amperes, A
®
852PM Chipset Platforms Design Guide
Platform Power Delivery Guidelines
Description
Definition Minimum
Vdd 2.3
VddQ 2.3
Vdd/2 + 0.05 V Vdd/2 – 0.05
Nominal Maximum
2.5 2.7
2.5 2.7
5.0
0.920
Vdd/2 Vdd/2 + 0.05
< 0.001
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