LINEAR Technology, represented in Australia by Soanar , has released the LTC3448, a 2.25MHz (or 1.5MHz) synchronous buck regulator which can deliver up to 600mA of continuous output current. When output current is greater than 3mA it switches at a constant frequency of 2.25MHz. If output current drops to 3mA or below it automatically transitions into a low-noise LDO mode consuming 32μA of quiescent current.
Output ripple is less than 5mV p-p in switching mode and is low noise in LDO mode, making it ideal for low noise applications such as handheld wireless applications. Using a current mode architecture it operates from an input voltage range of 2.5V to 5.5V, making it suitable for single-cell Li-Ion, multi-cell Alkaline or NiMH applications. It can generate output voltages as low as 0.6V, enabling it to power low-voltage DSPs and microcontrollers.
The user can set its switching frequency to either 1.5MHz or 2.25MHz and can synchronise the device up to 4MHz allowing the use of tiny, low-cost ceramic capacitors and inductors less than 1.2mm in height. Alternately, the part can be synchronised to an external clock. The combination of tiny externals and a 3mm x 3mm DFN-8 (or MSOP-8E) provide a compact footprint for space-conscious handheld applications.
The LTC3448 uses internal synchronous switches with an RDS(ON) of 0.35Ω and 0.4Ω to deliver efficiencies as high as 96%. It also uses low-dropout, 100% duty cycle operation to allow output voltages approaching VIN, further extending battery run-time. Light load quiescent current is only 32μA and less than 1μA in shutdown, ensuring maximum battery life.
The regulator’s LDO mode can be enabled automatically or via an external input. It is suitable for handheld applications requiring low noise operation and low quiescent currents.
The LTC3448EDD is available in a 3mm x 3mm DFN-8 package while the LTC3448EMS8E is available in a thermally enhanced MSOP-8 package.