82801DB Datasheet, PDF (52/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

Signal Description
2.19 Power and Ground
Table 2-19. Power and Ground Signals
Name
Vcc3_3
Vcc1_5
VccHI
V5REF
HIREF
VccSus3_3
VccSus1_5
V5REF_Sus
VccRTC
VccPLL
VBIAS
V_CPU_IO
Vss
Description
3.3 V supply for core well I/O buffers. This power may be shut off in S3, S4, S5 or G3
states.
1.5 V supply for core well logic. This power may be shut off in S3, S4, S5 or G3 states.
1.5 V supply for Hub Interface 1.5 logic.
1.8 V supply for Hub Interface 1.0 logic.
This power may be shut off in S3, S4, S5 or G3 states.
Reference for 5 V tolerance on core well inputs. This power may be shut off in S3, S4,
S5 or G3 states.
Analog Input. Expected voltages are:
• 0.9 V for HI 1.0 (Normal Hub Interface) Series Termination
• 350 mV for HI 1.5 (Enhanced Hub Interface) Parallel Termination
This power is shut off in S3, S4, S5, and G3 states.
3.3 V supply for resume well I/O buffers. This power is not expected to be shut off
unless the system is unplugged.
1.5 V supply for resume well logic. This power is not expected to be shut off unless the
system is unplugged.
Reference for 5 V tolerance on resume well inputs. This power is not expected to be
shut off unless the system is unplugged.
3.3 V (can drop to 2.0 V min. in G3 state) supply for the RTC well. This power is not
expected to be shut off unless the RTC battery is removed or completely drained.
NOTE: Implementations should not attempt to clear CMOS by using a jumper to pull
VccRTC low. Clearing CMOS in an Intel^® ICH4-based platform can be done
by using a jumper on RTCRST# or GPI, or using SAFEMODE strap.
1.5 V supply for core well logic. This signal is used for the USB PLL. This power may
be shut off in S3, S4, S5, or G3 states.
RTC well bias voltage. The DC reference voltage applied to this pin sets a current that
is mirrored throughout the oscillator and buffer circuitry. See Section 2.20.4.
Powered by the same supply as the processor I/O voltage. This supply is used to drive
the processor interface outputs.
Grounds.
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Intel^® 82801DB ICH4 Datasheet