Advanced I/O Controller with Motherboard GLUE Logic
Datasheet
The second possible sequence, shown in the figure below, is a normal powerdown sequence. The
nBACKFEED_CUT signal goes from low to high when nSLP_S3 goes low, and nSLP_S5 goes from high
to low 30usec to 65usec (t3) later.
The LATCHED_BF_CUT signal goes high when nBACKFEED_CUT goes high and then
LATCHED_BF_CUT returns to low when nSLP_S5 goes low.
The nBACKFEED_CUT stays high and nSLP_S5 stays low for an indeterminate time and then nSLP_S5
will go high. A minimum of 1msec (t4) later, nBACKFEED_CUT will go low and the system returns to the
end of the power-up sequence when nSLP_S3 and PWRGD_PLATFORM goes high. Typical measured
values of t4 are approximately 250msec. During all transitions, the propagation delays, rise and fall times
and power regulation times for LATCHED_BF_CUT are as described in Figure 7.17. The first sequence
can start at the end of this power-up sequence at any time.
nSLP_S3
PWRGD_PS
t4
t3
nBACKFEED_CUT
nSLP_S5
Tpropr
Tpropf
LATCHED_BF_CUT
Tr
Tf
Figure 7.17 – Latched Backfeed Cut Sequence 2
Table 7.46 – Latched Backfeed Cut Sequence 1 and 2 Timing
NAME
Tr
DESCRIPTION
MIN
TYP
MAX
UNITS
us
LATCHED_BF_CUT rise time. Measured
1
from 10% to 90%.
Tf
LATCHED_BF_CUT fall time. Measured from
90% to 10%.
1
us
ns
Tpropf LATCHED_BF_CUT high to low propagation
50
delay. Measured from
nBACKFEED_CUT/nSLP_S5 threshold to
90% of LATCHED_BF_CUT
Tpropr LATCHED_BF_CUT low to high propagation
50
ns
delay. Measured from
nBACKFEED_CUT/nSLP_S5 threshold to
10% of LATCHED_BF_CUT
CO
CL
t3
Output Capacitance
Load Capacitance
25
50
60
pF
pF
us
nBACKFEED_CUT inactive to nSLP_S5
30
1
active
t4
nSLP_S5 inactive to nBACKFEED_CUT
active
250
ms
The following figure shows a flowchart of the logic.
Revision 1.8 SMSC/Non-SMSC Register Sets (02-24-05)
150
SMSC LPC47M182
DATASHEET
SMSC [ SMSC CORPORATION ]
