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LTC1472 Datasheet(PDF) 6 Page - Linear Technology |
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LTC1472 Datasheet(HTML) 6 Page - Linear Technology |
6 / 16 page 6 LTC1472 1472fa 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 0.1 µA 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 100 µs 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. |
Similar Part No. - LTC1472 |
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Similar Description - LTC1472 |
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