Power Electronics

PMU Integrates Buck-Boost Converter and Charger

National Semiconductor’s LP3910, a flexible power management unit (PMU), includes an integrated buck-boost converter and multiple-output power management devices. In addition, the LP3910 PMU includes a dual-source battery charger to power a device from a wall adapter or USB and a digital I2C-compatible interface.

The integrated battery charger supports power routing, which allows system usage immediately after an external power source has been detected. The I2C interface allows design engineers to customize electrical specifications such as output voltage and switching modes to the end application.

In portable media players where mini hard disk drives typically require a 3.3-V supply, a buck-boost converter extends battery life. Li-ion batteries, a popular choice for portable media players, have an operating voltage range of 2.9 V to 4.2 V. When the Li-ion battery is fully charged, the converter steps the voltage down to supply the hard disk drive. When the battery voltage is lower than 3.3 V, the converter steps up the voltage. This technique increases the run-time of the player up to 10% over the run-time achieved by a traditional buck converter.

The highly-integrated LP3910 flexible PMU includes two buck regulators that provide up to 96% efficiency. Power consumption is further minimized through a dynamic voltage-scaling feature that enables the device to adjust or scale the output voltage in real time to match the computing workload and clock frequencies of the corresponding processors.

Available in a 6 mm x 6 mm 48-pin LLP package, National’s LP3910 is a programmable system PMU that is optimized for portable media players with hard disk drives. It incorporates a 4-channel, 8-bit ADC for managing the battery usage and a dual-source Li-ion/polymer battery charger. For applications using Flash memory or products without a hard drive, National offers the LP3913 with the same features as the LP3910, but a 500-mA buck converter replaces the buck-boost converter.

Available now, the LP3910 is priced at $4.84 and the LP3913 is $4.40 each, both in 1000-unit quantities.

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