The AAT4621 SmartSwitch is a current limited P-channel MOSFET power switch designed for high-side loadswitching applications in PC Card GSM/GPRS/3G modem cards. Used in conjunction with a super capacitor, the AAT4621 will ensure that the power ratings of the
PCMCIA host are not exceeded at any time. Featuring two independent, programmable current limits and a power loop, the AAT4621 can ensure that the super capacitor can be charged without exceeding PCMCIA specifications. 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.