Farnell LTC3521 buck-boost with step-down DC/DC converters

The LTC3521 combines a synchronous 1A buck-boost DC/DC converter with dual 600 mA synchronous step-down DC/DC converters to offer three output rails with efficiencies as high as 95%. Its input range of 1.8 to 5.5 V makes it compatible with all types of PC card slots, USB and single-cell Li-Ion or dual/triple-cell alkaline/NiCd/NiMH applications.

Its synchronous buck boost channel topology provides a continuous transition through all operating modes, making it suitable for applications that must maintain a constant output voltage even as the battery voltage declines below the output. In many cases this can add up to 20% more battery run-time.

Its buck-boost channel can give constant output voltages between 1.8 and 5.25, whereas each of its synchronous buck channels can deliver outputs between 0.6 and 5.25 V, making it suitable for a wide range of handheld applications.

The device’s constant 1.1 MHz switching frequency offers low noise operation while minimising the size of the external components.

The device’s synchronous buck-boost channel offers continuous conduction operation to maximise efficiency over a wide input voltage range while minimising switching noise. The buck converters use current mode control and synchronous rectification to give optimal efficiency.

The device’s selectable burst mode operation requires only 30 µA of quiescent current and shutdown current is less than 2 µA. For applications requiring the lowest possible noise, it can be configured to run in fixed frequency PWM mode, reducing noise and potential RF interference. Other features include internal compensation, integrated soft-start and power good outputs for each channel.

The EUF is available in a 24-lead QFN package and the EFE is available in a 20-lead thermally enhanced TSSOP package.