User Manual

Datasheet 43

Electrical Specifications
• Slew Rate Decay (downward voltage only and it is a function of the output
capacitance's time constant) commands. Tab l e 5-3, “VR12.5 Reference Code
Voltage Identification (VID) Table” on page 45 includes SVID step sizes and DC
shift ranges. Minimum and maximum voltages must be maintained as shown in
Section 5-10, “Voltage Specification” .
The VRM or EVRD used must be capable of regulating its output to the value defined by
the new VID.
Power source characteristics must be guaranteed to be stable whenever the supply to
the voltage regulator is stable.
5.2.8.5 SetVID Fast Command
The SetVID_Fast command contains the target VID in the payload byte. The range of
voltage is defined in the VID table. The VR should ramp to the new VID setting with a
fast slew rate as defined in the slew rate data register. It is minimum of 20 mV/µs,
depending on the amount of decoupling capacitance.
The SetVID_Fast command is preemptive. The VR interrupts its current processes and
moves to the new VID. The SetVID_Fast command operates on 1 VR address at a time.
This command is used in the processor for package C6 fast exit.
5.2.8.6 SetVID Slow
The SetVID_Slow command contains the target VID in the payload byte. The range of
voltage is defined in the VID table. The VR should ramp to the new VID setting with a
"slow" slew rate as defined in the slow slew rate data register. The SetVID_Slow is
nominally 4x slower than the SetVID_Fast slew rate.
The SetVID_Slow command is preemptive, the VR interrupts its current processes and
moves to the new VID. This is the instruction used for normal P-state voltage change.
This command is used in the processor for the Intel Enhanced Intel SpeedStep
Technology transitions.
5.2.8.7 SetVID Decay
The SetVID_Decay command is the slowest of the DVID transitions. It is normally used
for VID down transitions. The VR does not control the slew rate; the output voltage
declines with the output load current only.
The SetVID_Decay command is preemptive; the VR interrupts its current processes
and moves to the new VID. This command is used in the processor for package C6
entry, allowing capacitor discharge by the leakage; thus, saving energy. This command
is normally used in VID down direction in the processor package C6 entry.
5.2.8.8 SVID Power State Functions: SetPS
The processor has three power state functions and these will be set seamlessly using
the SVID bus and the SetPS command. Based on the power state command, the SetPS
commands send information to the VR controller to configure the VR to improve
efficiency, especially at light loads. For example, typical power states are:
• PS0(00h): Represents full power or active mode
• PS1(01h): Represents a light load 5A to 20A
• PS2(02h): Represents a very light load <5A