LPC47M172-NR SMSC [SMSC Corporation], LPC47M172-NR Datasheet - Page 140

• Manufacturer Part Number: LPC47M172-NR
• Description: ADVANCED I/O CONTROLLER WITH MOTHERBOARD GLUE LOGIC
• Manufacturer: SMSC [SMSC Corporation]

Advanced I/O Controller with Motherboard GLUE Logic
Datasheet
SMSC/Non-SMSC Register Sets (Rev. 02-27-04)
PWRGD_PS
PWRGD_PS
NOTE: The switch is implemented as an n-channel switch that will not pass a full voltage swing.
It provides a current path to ground.
The board designer should treat each signal pair to the switch as a separate bus with a
resistance in the path.
The maximum resistance of the switch between any bus to any other bus is 25ohms (when the
switch is on). When the switch is off the impedance is Hi-Z and the current is zero.
The design requires pull-ups on each of the busses shown above.
It is recommended that the pullups be selected so that the total maximum current on both
busses does not exceed 2mA to limit the voltage drop across the switch.
CLK GEN
DIMMS,
CNR,
ICH,
0
1
1
0
1
1
SMB_CLK_M
SMB_DAT_M
PWRGD_PS
SMB_DAT_M
SMB_CLK_M
3.6V (max)
Don’t Care
2.7k
3.6V (max)
Don’t Care
0V
0V
VCC
Table 7.35 - SMB_CLK Isolation Logic
Table 7.36 - SMB_DAT Isolation Logic
Figure 7.11 - SMBUS Isolation Circuit
2.7k
DATASHEET
LPC47M172
SEE NOTE
25ohm
25ohm
Max
Max
Page 140
SMB_DAT_R
EN
Don’t Care
3.6V (max)
SMB_CLK_R
Don’t Care
3.6V (max)
0V
0V
SMB_CLK_R
SMB_DAT_R
CURRENT DIRECTION ACROSS THE
CURRENT ACROSS THE SWITCH
Current flows from SMB_CLK_R or
Current flows from SMB_DAT_R or
2.7k
VTR
No Current flow (0 mA)
No Current flow (0 mA)
No Current flow (0 mA)
No Current flow (0 mA)
SMB_DAT_M
SMB_CLK_M
2.7k
SWITCH
ICH, PCI
SMSC LPC47M172