The AAT4651 SmartSwitch is a single channel PC card (PCMCIA) power switch. It is used to select between two different voltage inputs, each between 2.7V and 5.5V. An internal switch powers the circuitry from whichever input voltage is higher. The device's output, VCC, is slew rate controlled and current limited, in compliance with PC card specifications. The current limit response time to a short circuit is typically 1s. The internal P-channel MOSFET switches are configured to break before make; that is, both switches cannot be closed at the same time. Controlled by a 2-bit parallel interface, the three states for VCC are VCC5, VCC3, or ground. When in the ground state, VCC is pulled to ground by an 200 resistor. An open drain FAULT output is asserted during over-current conditions. During power-up slewing, FAULT also signals that VCC is out of tolerance. An internal over-temperature sensor forces VCC to a high impedance state when an over-temperature condition exists. Quiescent current is typically a low 15A, as long as ICC is less than approximately 500mA. Above this load current, the quiescent current increases to 200A.