Synchronous buck-boost DC/DC converters reduce quiescent current budget

Synchronous current mode buck-boost converters from Linear Technology, deliver up to 600mA of continuous output current from a variety of input sources, including single- or multiple-cell batteries, as well as battery-powered instruments, portable military radios, low power sensors and solar panel post-regulator/charger circuits and supercapacitors.

The LTC3130 and LTC3130-1 have an input range of 2.4 to 25V and 1.0 to 25V output range; although the LTC3130 is adjustable. The result is a regulated output with inputs above, below or equal to the output. User-selectable Burst Mode operation lowers quiescent current to 1.6microA (1.2microA at no load) to improve light load efficiency and extending battery run time. The proprietary buck-boost topology is claimed to provide low noise, jitter-free switching through all operating modes. This makes them suitable for RF and precision analogue applications that are sensitive to power supply noise, says the company. Programmable maximum power point control (MPPC) capability ensures maximum power delivery from power sources such as photovoltaic cells. The LTC3130-1 additionally offers four user-selectable fixed output voltages of 1.8, 3.3, 5.0 and 12V, eliminating the resistor divider required for the adjustable output version.

Both include four internal low RDSON N-channel MOSFETs to deliver efficiencies of up to 95 per cent. Due to the low quiescent current, converter start-up can be achieved from sources as low as 7.5microW, for applications powered by weak sources, including thin film solar cells. Alternatively, Burst Mode operation can be disabled, offering low noise continuous switching. The constant 1.2MHz switching frequency ensures low noise and high efficiency, says the company, while minimising the size of the external components. Built-in loop compensation and soft-start also reduce external parts count and simplify design. Other features include a power-good indicator, pin-selectable current limit, an accurate ‘run’ pin threshold, an external VCC input and thermal shutdown.

Both devices are available in thermally enhanced 20-lead 3.0 x 4.0mm QFN package and 16-lead MSOPs. E- and I-grade devices are specified over -40 to +125 degree C.


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