Synchronous buck-boost DC/DC converter enables multi-inputs

11th March 2015
Siobhan O'Gorman

A dual input, wide voltage range synchronous buck-boost DC/DC converter, with an integrated low loss PowerPath control, has been released by Linear Technology. Featuring a unique power switch architecture, the LTC3118 provides high efficiency operation from either input source to a programmable output voltage above, below or equal to the inputs. 

The device’s dual input capability makes it suitable for applications that use batteries or supercaps as secondary or backup inputs, in case the primary input is interrupted. Similarly, applications that use multiple sources such as a wall adapter and Li-Ion cells could utilise the dual input and buck-boost capability of the converter. The LTC3118 can deliver up to 2A of continuous output current from a wide range of power sources, including single or multiple cell batteries, supercapacitor stacks and wall adapters. The device’s 2.2-18V input range and 2.0-18V output range can provide a regulated output with inputs above, below or equal to the regulated output.

The converter uses a low noise, current mode buck-boost topology architecture with a fixed 1.2MHz switching frequency. This unique design provides a continuous, jitter-free transition between buck and boost modes, making it suitable for RF and other noise-sensitive applications. The device’s integrated low loss PowerPath controller is user programmable to prioritise and seamlessly transition between inputs while maintaining output voltage regulation. The combination of tiny externals and a 4x5mm QFN or TSSOP-28E package provides a compact solution footprint.

The LTC3118 includes four internal low RDS(ON) N-channel MOSFETs to deliver efficiencies of up to 94%. User-selectable Burst Mode operation lowers input quiescent current to only 50µA, improving light load efficiency and extending battery run time. For noise-sensitive applications, Burst Mode operation can be disabled. Other features include soft-start, overvoltage protection, short-circuit protection, thermal shutdown and output disconnect.

The LTC3118 is available in a 24-lead 4x5mm QFN package (LTC3118EUFD) and a thermally enhanced 28-lead TSSOP package (LTC3118EFE). Both packages are priced at $5.75 each and sold in 1,000-piece quantities. Industrial grade versions are guaranteed to operate over the -40 to +125°C operating junction temperature range. High temperature grade versions (LTC3118HUFD and LTC3118HFE) are guaranteed to operate over the -40 to +150°C operating junction temperature range, while military plastic grades (LTC3118MPUFD and LTC3118MPFE) are guaranteed to operate over -55 to +150°C. All versions are available from stock.

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