Linear Tech step-down switching regulator provides 300mA output

The LTC3405 synchronous step-down switching regulator delivers up to 300mA of output current from a 2.5V to 5.5V input voltage range making it suitable for single-cell Li-ion battery-powered applications such as cellular phones, PDAs, and digital cameras.

The device also uses a constant frequency, synchronous Buck switching topology to obtain efficiencies as high as 96 percent. Its 1.5MHz switching frequency allows the use of small, surface-mount components and keeps the switching noise well above the passband of most communication systems.

The chip also uses internal synchronous switches to increase efficiency and eliminate the need for an external Schottky diode.

The LTC3405 offers a "burst mode" feature that allows the internal power MOSFETs to operate intermittently based on load demand and reduces the quiescent current to 20?A at no-load and <1?A during shutdown.

This selectable feature is also passive during synchronization or when the sync/mode pin is pulled low preventing low frequency ripple from interfering with audio circuitry.

The LTC3405's current mode operation maintains a two percent output voltage regulation over all line and load conditions. It has a 100 percent duty cycle capability that provides low dropout operation, extending battery run time in portable applications. A 0.8V feedback reference voltage supports the low output voltage.

Housed in a 1mm-high, 6-lead ThinSOT package, the LTC3405 is priced at $1.61 each in quantities of 1,000.