Advanced I/O Controller with Motherboard GLUE Logic
Datasheet
7.31.3 5V Standby Reference Generation
REF5V_STBY is generated in the same manner as REF5V, but in reference to V_5P0_STBY and
VTR instead. REF5V_STBY serves the same purpose as REF5V, but tracks different power supplies.
REF5V_STBY is an analog output signal that tracks either VTR or V_5P0_STBY, whichever is greater in
amplitude.
Upon motherboard power-up, REF5V_STBY is an analog output signal that tracks either VTR or
V_5P0_STBY (through an external pull-up resistor), whichever is greater in amplitude. REF5V_STBY
becomes a high impedance input while tracking the V_5P0_STBY power supply.
REF5V_STBY is powered by VTR when VTR > V_5P0_STBY.
Table 7.26 – REF5V_STBY
STANDBY SUPPLY
V_5P0_STBY < VTR
V_5P0_STBY > VTR
REF5V_STBY
VTR
Hi-Z
Backdrive
V_5P0_STBY
Protection
V)
VTR (3.3
1k
BY
V_ST
REF5
SMSC I/O
Figure 7.9 – REF5V_STBY
Note: the maximum voltage drop across the diode is 350mV.
7.31.4 Reference Timings
See Figure 13.25 to Figure 13.28 in the “Timing Diagrams” section.
7.32 IDE Reset Output Pin
nIDE_RST is an open drain buffered copy of nPCI_RESET. This signal requires an external 1kohm pull-up
to VCC5V.
This signal will be low when VCC5V=0 since it is externally pulled up to VCC5V.
SMSC LPC47M182
139
Revision 1.8 SMSC/Non-SMSC Register Sets (02-24-05)
DATASHEET
SMSC [ SMSC CORPORATION ]
