3.3 VOLT OPERATION / 5 VOLT TOLERANCE
The LPC47S42x is a 3.3 Volt part. It is intended
solely for 3.3V applications. Non-LPC bus pins
are 5V tolerant; that is, the input voltage is 5.5V
max, and the I/O buffer output pads are
backdrive protected.
The LPC interface pins are 3.3 V only. These
signals meet PCI DC specifications for 3.3V
signaling. These pins are:
LAD[3:0]
nLFRAME
nLDRQ
nLPCPD
The input voltage for all other pins is 5.5V max.
These pins include all non-LPC Bus pins and the
following pins:
nPCI_RESET
PCI_CLK
SER_IRQ
nIO_PME
POWER FUNCTIONALITY
The LPC47S42x has two power planes: VCC
and VTR.
VCC Power
The LPC47S42x is a 3.3 Volt part. The VCC
supply is 3.3 Volts (nominal). See the
Operational
Description
Maximum Current Values subsection.
VTR Support
The LPC47S42x requires a trickle supply (V
TR
) to
provide sleep current for the programmable
wake-up events in the PME interface when V
CC
is removed. The VTR supply is 3.3 Volts
(nominal). See the Operational Description
Section. The maximum VTR current that is
required depends on the functions that are used
in the part. See Trickle Power Functionality
subsection and the Maximum Current Values
subsection. If the LPC47S42x is not intended to
provide wake-up capabilities on standby current,
14
Section
and
the
V
TR
can be connected to V
CC
. The V
TR
pin
generates a V
TR
Power-on-Reset signal to
initialize these components.
Note: If V
TR
is to be used for programmable
wake-up events when V
CC
is removed, V
TR
must
be at its full minimum potential at least 10
μ
s
before V
CC
begins a power-on cycle. When V
TR
and V
CC
are fully powered, the potential
difference between the two supplies must not
exceed 500mV.
Internal PWRGOOD
An internal PWRGOOD logical control is
included to minimize the effects of pin-state
uncertainty in the host interface as V
CC
cycles on
and off. When the internal PWRGOOD signal is
“1” (active), V
CC
> 2.3V (nominal), and the
LPC47S42x host interface is active. When the
internal PWRGOOD signal is “0” (inactive), V
CC
≤
2.3V (nominal), and the LPC47S42x host
interface is inactive; that is, LPC bus reads and
writes will not be decoded.
The
LPC47S42x
device
CLOCKI32, KDAT, MDAT, IRRX, nRI1, nRI2,
RXD2 and most GPIOs (as input) are part of the
PME interface and remain active when the
internal PWRGOOD signal has gone inactive,
provided
V
TR
is
GP53/TXD2/IRTX, GP60/LED1 and GP61/LED2
pins also remain active when the internal
PWRGOOD signal has gone inactive, provided
V
TR
is powered. See Trickle Power Functionality
section.
32.768 kHz Trickle Clock Input
The LPC47S42x utilizes a 32.768 kHz trickle
clock input to supply a clock signal for the fan
tachometer logic, WDT, LED blink and wake on
specific key function. See the following section
for more information.
Indication of 32kHz Clock
There is a bit to indicate whether or not the
32kHz clock input is connected to the
pins
nIO_PME,
powered.
The