AnalogicTech announced the AAT4620, a P-channel current-limited MOSFET power switch for high-side load-switching applications in PC modem cards. Integrating all the circuitry required to limit current, protect the PC Card connector, continuously charge the capacitor, and notify the system when it is ready for use, this new device ensures that a Super Capacitor, typically used to average out high pulse currents, can be quickly charged without exceeding the host power supply specifications. The AAT4620 offers two independent, programmable current limits to control current during host/card negotiation. As long as thermal dissipation is low, the integrated current limiting will allow the capacitor to charge until it reaches 98% of its final value. Set by two external resistors, the current limits support 10 % +/- accuracy over the normal operating temperature range. An integrated digital power loop automatically monitors and reduces the charging current to a safe level when high levels of charge result in excessive temperature and threaten to send the chip into thermal shutdown.

By regulating charge current and therefore die temperature, this circuit ensures the super capacitor charges continuously and as quickly as possible. Integrated reverse blocking protection prevents discharge of the Super Capacitor to the power supply. A system-ready output pin with externally programmable hysteresis alerts the system when the super capacitor is fully charged and ready for use. The AAT4620 also features a quiescent current of only 40 uA typical. In shutdown mode, the supply current drops to 1 uA. The device is available in a Pb-free, 12-pin TSOPJW package and specified across the -40 degrees to +85 degrees C temperature range. It sells for $1.34 each in 1,000 piece quantities.