The AAT4621 SmartSwitch™ is a reverse-blocking, current limited P-channel MOSFET power switch designed for high side load-switching applications in WiMAX, CDMA or GSM/GPRS/3G modem cards. Examples are PC Card, Express Cards, Compact Flash cards. Used in conjunction with a super capacitor, and featuring dual current limits, the AAT4621 will ensure that the power rating of the host supply is not exceeded at any time. The current limit is set by two external resistors allowing a ±10% current limit accuracy over the normal operating temperature range. The switch can be controlled from either of the two enable inputs and in the off condition will block currents in both directions. The AAT4621 also incorporates a System READY function which can advise the system that the super capacitor is fully charged and ready for use. Adjustable hysteresis is provided with the addition of an external resistor. The quiescent supply current is typically a low 40µA. In shutdown mode, the supply current decreases to less than 1µA. The AAT4621 is available in a thermally enhanced, Pb-free, 14-pin TDFN33 package and is specified over the -40°C to 85°C temperature range.