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LTC1472

Protected PCMCIA VCC and VPP Switching Matrix

Linear Technology 

LTC1472

PIN FUNCTIONS

Enable Input (Pins 3,4,7,8)

The two VCC 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 5VIN 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 VCC NMOS switches are

powered by charge pumps from the 5VIN supply, and the

gates of the VPP NMOS switches are powered by charge

pumps powered from the VDD supply when 12V is not

present at the VPPIN 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.

VPPIN Supply (Pin 5)

The VPPIN supply pin serves two purposes. The first

purpose is to provide power and gate drive for the VPPIN-

VPPOUT switch. The second purpose is to provide optional

12V gate drive for the VCC(IN)-VPPOUT switch. If, however,

this 12V power is not available, gate drive is obtained

automatically from the 5V VDD supply by an internal 5V to

12V charge pump converter.

VDD Supply (Pin 9)

The VDD 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 VPPOUT pin

is programmed to 0V or Hi-Z and only rises to micropower

levels when the VPP switches are active.

VCC(IN) Supply (Pin 12)

The VCC(IN) supply pin is typically connected directly to the

VCC(OUT) pin from the VCC 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 VCC(IN)-VPPOUT switch and therefore does not

consume any power when unloaded or turned off.

5VIN Supply (Pin 2)

The 5VIN 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 VCC

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 5VIN power

is removed to ensure that both VCC NMOS switch gates are

fully discharged and both switches are in the high imped-

ance mode.

3VIN Supply (Pins 14,15)

The 3VIN 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.

VCC(OUT) and VPPOUT Output (Pins 1,11,16)

The VCC 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, VCC, 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.

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