Ultra-low quiescent current for buck-boost converter

March 19, 2013 // By Paul Buckley
Linear Technology has released a synchronous buck-boost converter that delivers up to 200 mA of continuous output current from a wide variety of input sources including single or multiple-cell batteries as well as solar panels and supercaps.

The device's 2.42 V to 15 V input range and 1.4 V to 15.75 V output range provide a regulated output with inputs above, below or equal to the output. The low noise buck-boost topology incorporated in the LTC3129 provides a continuous transition through all of the operating modes, making it suitable for applications that must maintain a constant output voltage, even as the input source voltage transitions through the output voltage. It also includes programmable maximum power point control (MPPC) capability, ensuring maximum power extraction from non-ideal power sources such as photovoltaic cells.

Quiescent current of only 1.3 µA makes the LTC3129 appropriate for always-on and energy harvesting applications in which extended battery run time is of primary importance. The LTC3129’s constant 1 MHz switching frequency ensures low noise and high efficiency, while minimising the size of the external components. The combination of tiny externals and a 3 mm x 3 mm QFN or MSOP-16E package provides a very small solution footprint.

The LTC3129 includes four internal low RDSON N-channel MOSFETs to deliver efficiencies of up to 95%. User selectable Burst Mode operation lowers quiescent current to only 1.3 µA improving light load efficiency and extending battery run time. For noise sensitive applications, Burst Mode operation can be disabled, offering low noise continuous switching. Other features include a power good indicator, current-mode control, internal compensation thermal shutdown and output disconnect.

The LTC3129-1 shares all of the features of the LTC3129, but offers eight fixed output voltages from 2.5 V to 15 V. These outputs are user-programmable and eliminate the resistor divider required on the adjustable version.

Both the LTC3129EUD and LTC3129EUD-1 are available in a 16-lead 3mm x 3mm QFN package, whereas the LTC3129EMSE and LTC3129EMSE-1 are offered in a thermally enhanced 16-lead MSOP package. Pricing starts at $2.95 (1000). Industrial grade versions, the LTC3129IUD, LTC3129IUD-1, LTC3129IMSE and LTC3129IMSE-1, are guaranteed to operate over the -40°C to 125°C operating