Electrical Specifications
52
Datasheet, Volume 1
7.1.8.2
Decoupling Guidelines
Due to its large number of transistors and high internal clock speeds, the processor is
capable of generating large current swings between low and full power states. This may
cause voltages on power planes to sag below their minimum values if bulk decoupling is
not adequate. Large electrolytic bulk capacitors (C
BULK
), help maintain the output
voltage during current transients; for example, coming out of an idle condition. Care
must be taken in the baseboard design to ensure that the voltages provided to the
processor remains within the specifications listed in
. Failure to do so can
result in timing violations or reduced lifetime of the processor.
The Voltage Identification (VID) specification for the V
CC,
V
SA
, and optionally the V
CCD
voltage are defined by the
VR12/IMVP7 Pulse Width Modulation (PWM) Specification
.
The reference voltage or the VID setting is set using the SVID communication bus
between the processor and the voltage regulator controller chip. The VID setting is the
nominal voltage to be delivered to the processor VCC, VSA, and the VCCD lands.
specifies the reference voltage level corresponding to the VID value
transmitted over serial VID. The VID codes will change due to temperature and/or
current load changes to minimize the power and to maximize the performance of the
part. The specifications are set so that a voltage regulator can operate with all
supported frequencies.
Individual processor VID values may be calibrated during manufacturing such that two
processor units with the same core frequency may have different default VID settings.
The processor uses voltage identification signals to support automatic selection of V
CC,
V
SA
, and if desired the V
CCD
power supply voltages. If the processor socket is empty
(SKTOCC_N high), or a “not supported” response is received from the SVID bus, then
the voltage regulation circuit cannot supply the voltage that is requested, the voltage
regulator must disable itself or not power on. Vout MAX register (30h) is programmed
by the processor to set the maximum supported VID code and if the programmed VID
code is higher than the VID supported by the VR, then VR will respond with a “not
supported” acknowledgement.
7.1.8.3.1
SVID Commands
The processor provides the ability to operate while transitioning to a new VID and its
associated processor core voltage. This is represented by a DC shift in the loadline. It
should be noted that a low-to-high or high-to-low voltage state change may result in as
many VID transitions as necessary to reach the target voltage. Transitions above the
maximum specified VID are not supported. The processor supports the following VR
commands:
• SetVID_fast (20 mV/µs for V
CC
, 10m V/µs for V
CC
/V
SA
/V
CCD
),
• SetVID_slow (5m V/µs for V
CC
, 2.5 mV/µs for V
CC
/V
SA
/V
CCD
), and
• Slew Rate Decay (downward voltage only and it’s a function of the output
capacitance’s time constant) commands.
includes SVID
step sizes and DC shift ranges. Minimum and maximum voltages must be
maintained as shown in
The VR used must be capable of regulating its output to the value defined by the new
VID. Power source characteristics must be ensured to be stable whenever the supply to
the voltage regulator is stable.
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