A new 7-V, 500-mA synchronous buck-boost dc-dc converter from Linear Technology offers designers extended battery run time in handheld applications. Using a single inductor, the LTC3534 delivers its output current to a regulated output above, below, or equal to the input.

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The device’s topology provides a continuous transfer through all operating modes, making it well-suited for three- or four-cell alkaline/nickel-cadmium/nickel-metal-hydride or single-cell lithium applications, which must maintain a constant output voltage even as the battery voltage declines below the output. A typical application is alkaline cells with an input voltage range of 3.6 to 6.4 V, powering a 5-V output rail.

In most cases, this buck-boost dc-dc converter can add up to 25% more battery runtime compared to a traditional single-ended primary inductance converter (SEPIC) solution. The converter’s constant 1-MHz switching frequency ensures low noise while minimizing the size of external components.

Two n-channel MOSFETs and two p-channel MOSFETs (215/275 mΩ and 260 mΩ, respectively) provide efficiencies of up to 94%. Burst-mode operation requires only 25 μA of quiescent current while shutdown current is less than 1 μA, further extending battery runtime.

If the application is noise sensitive, the pulse-width modulation (PWM) pin can be configured to provide forced continuous operation to reduce noise and RF interference. Other features include soft-start, current limiting, thermal shutdown, and output disconnect.

The LTC3534EDD is available from stock in a 16-lead, 3- by 5-mm dual flat no-lead (DFN) package. The LTC3534EGN is available in a 16-lead shrink small-outline package (SSOP) package. Both cost $3.15 each in quantities of 1000.

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