Boost convertors go linear when needed

A new family of synchronous 1.5A switch DC/DC boost convertors features linear regulation functionality for battery-powered electronics.

A new family of synchronous 1.5A switch DC/DC boost convertors features linear regulation functionality for battery-powered electronics.

The convertors reduce board space, provide up to 96% power conversion efficiency from an input voltage range of 0.9 to 5.5V, and enable designers to power innovative applications such as a white LED flash for wireless camera phones.

TI's new TPS6102x family of convertors support power supplies for PDAs, PC peripherals, wireless headsets and other products powered by either a one-, two- or three-cell alkaline, nickel-cadmium (NiCd), nickel metal-hydride (NiMH), or a one-cell lithium-ion (Li-ion) or lithium-polymer (Li-poly) battery.

The highly flexible convertors provide 200mA from a 0.9V input when using a single-cell alkaline battery.

The TPS6102x can also be used for generating 5V at 500mA from a 3.3V rail or a Li-ion battery at up to 96% power conversion efficiency.

The boost convertors generate a stable output voltage that can be adjusted by an external resistor divider or fixed internally on the chip.

For maximum power efficiency, the integrated device uses a synchronous rectifier based on a pulsewidth modulation (PWM) controller.

Unlike typical boost convertors, the TPS6102x family can operate in a down-mode with linear regulation if the input voltage reaches or exceeds the output voltage.

In this mode, the control circuit changes the behaviour of the rectifying integrated switching transistor.

The convertor then operates as a linear regulator by setting a voltage drop across the transistor high enough to regulate the output voltage.

As a result, the output voltage remains regulated even if the input voltage exceeds the nominal output voltage.

Further improving battery life, the TPS6102x enters a power save mode at light loads and can be fully disabled to minimise battery drain.

During shutdown, the load is completely disconnected from the battery to avoid battery depletion.

For applications that require a dual output, the popular TPS611xx family of DC/DC boost convertors with integrated LDO features two independent voltage regulators in a small 4 x 4mm QFN package.

The TPS6102x family of convertors is available today in volume from TI and its authorised distributors.

The synchronous DC/DC convertors come in a 10-pin 3 x 3mm QFN package, and are priced in quantities of 1000 at $1.39 per unit.

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