6
LTC1472
1472fa
PIN FUNCTIONS
UUU
Enable Input (Pins 3,4,7,8)
The two V
CC
and two VPP Enable inputs are designed to
interface directly with industry standard PCMCIA control-
lers. They are high impedance CMOS gates with ESD
protection diodes to ground, and should not be forced
above 5V
IN
or below ground. Both sets of inputs have
about 100mV of built-in hysteresis to ensure clean switch-
ing between operating modes.
Shutdown Output (Pin 6)
The LTC1472 is designed to operate
without
continuous
12V power. The gates of the V
CC
NMOS switches are
powered by charge pumps from the 5V
IN
supply, and the
gates of the VPP NMOS switches are powered by charge
pumps powered from the V
DD
supply when 12V is not
present at the VPP
IN
pin (see Application Information for
more details). Therefore, the external 12V regulator can be
shut down most of the time, and only turned on when
programming the socket VPP pin to 12V.
The shutdown output is active high; i.e. the system 12V
regulator is shut down when this output is held high and
turned on when this output is held low.
VPP
IN
Supply (Pin 5)
The VPP
IN
supply pin serves two purposes. The first
purpose is to provide power and gate drive for the VPP
IN
-
VPP
OUT
switch. The second purpose is to provide optional
12V gate drive for the V
CC(IN)
-VPP
OUT
switch. If, however,
this 12V power is not available, gate drive is obtained
automatically from the 5V V
DD
supply by an internal 5V to
12V charge pump converter.
V
DD
Supply (Pin 9)
The V
DD
pin provides power for the input, charge pump
and control circuitry for the VPP section of the LTC1472
and therefore must be continuously powered. The standby
quiescent current is typically 0.1µA when the VPP
OUT
pin
is programmed to 0V or Hi-Z and only rises to micropower
levels when the VPP switches are active.
V
CC(IN)
Supply (Pin 12)
The V
CC(IN)
supply pin is typically connected directly to the
V
CC(OUT)
pin from the V
CC
switch section of the LTC1472.
It can also be connected directly to a 3.3V or 5V power
supply if desired. This supply pin does not provide any
power to the internal control circuitry and is simply the
input to the V
CC(IN)
-VPP
OUT
switch and therefore does not
consume any power when unloaded or turned off.
5V
IN
Supply (Pin 2)
The 5V
IN
supply pin serves two purposes. The first pur-
pose is as the power supply input for the 5V NMOS switch.
The second purpose is to provide power for the input, gate
drive and protection circuitry for both the 3.3V and 5V V
CC
switches,
this pin must be continuously powered
.
The enable inputs should be turned off (both asserted high
or both asserted low) at least 100µs before the 5V
IN
power
is removed to ensure that both V
CC
NMOS switch gates are
fully discharged and both switches are in the high imped-
ance mode.
3V
IN
Supply (Pins 14,15)
The 3V
IN
supply pin serves as the power supply input for
the 3.3V switch. This pin does not provide any power to the
internal control circuitry and therefore does not consume
any power when unloaded or turned off.
V
CC(OUT)
and VPP
OUT
Output (Pins 1,11,16)
The V
CC
output of the LTC1472 is switched between the
three operating states: OFF, 3.3V, and 5V. The VPP output
is switched between four operating states: 0, V
CC
, 12V and
Hi-Z. Both pins are protected against accidental short-
circuit conditions to ground by independent SafeSlot
foldback current-limit circuitry which protects the socket,
card and the system power supplies against damage. A
second level of protection is provided by independent
thermal shut down circuitry which protects each switch
against overtemperature conditions.
