Dual Step-Down Power Supply Controller Suits Portables

Intended for use in notebook PCs and other battery-operated equipment such as PDAs and wireless data terminals, the LM2640 dual adjustable step-down switching power supply controller is a high-efficiency device combining two separate voltage controllers, linear regulator and a precision reference, all on a single chip. Its output voltages, adjustable between 2.2V and 6V, are typically set at 5V and 3.3V. The 5V linear regulator can also provide system back-up voltage, remaining on even when the dual synchronous controllers and 2.5V reference are shut down. The device takes advantage of the highest performance n-channel MOSFET technology to achieve high output current. In typical 3A applications, efficiencies of 92% and greater are said to be common. Under light load conditions, the devices uses a pulse-skipping mode to increase efficiencies over a 1000:1 load current range. Protection circuitry include programmable soft-start, thermal shutdown, undervoltage and overvoltage latch-off, cycle-by-cycle current limit, and latch-off current limits. The device is offered in 28-pin TSSOP.