Quad-output PMUs ease design and save space

National Semiconductor Corp. has added two new integrated power management units (PMUs) to its portfolio. The company said these PMUs are designed to power mid-range, quad-output applications, like low-power FPGAs, microprocessors and DSPs. The LP3906 and LP3905 PMUs each feature two high-efficiency buck regulators and two ultralow-noise, low-dropout regulators (LDOs). This level of integration simplifies system design and increases space efficiency, National said.

LP3906 PMU
The LP3906 PMU has an I₂C-compatible interface for programmability. This digital interface allows the use of the same device for multiple solutions requiring different output voltages. By including dynamic voltage scaling with 96 percent conversion efficiency, the power consumption of the powered device, such as a microprocessor, is reduced, according to National, thus maximizing the power efficiency of the entire system.

Applications include powering an embedded processor, in which each switching regulator drives the core and input/output while each LDO supplies analog and peripheral functions. In FPGA applications, the dual regulators power the core and I/O voltages, and the dual LDOs power the auxiliary voltages supplying the embedded peripherals such as communication engines.

"The small footprint of National's LP3906 is a great complement to our cost-optimized Spartan-3E FPGA platform," said Steve Knapp, senior applications manager of the general products division at Xilinx Inc. "National's LP3906 is fully programmable through an I?C interface and can control supply voltage ramps. With quad regulators in a single package, we can eliminate additional discrete components and address the same cost-effective board efficiency needs that our Spartan-3E customers demand for their leading-edge solutions."

The LP3906 PMU is packaged in a 24-pin thermally enhanced LLP that measures 4-by-5mm. The device promises a simple, highly efficient and flexible solution to efficiently drive core I/O and auxiliary power. It has two integrated 1.5A, high-efficiency buck regulators and two 300mA linear regulators with an I?C compatible interface for programmability.

The dual buck regulators have a programmable output voltage range of 0.8-3.5V with up to 96 percent efficiency. This high efficiency is achieved by intelligent automatic switching between PWM and PFM modes. The dual linear regulators have a programmable output voltage range of 1-3.5V. The high-speed serial interface for independent control of device functions and settings enables features like dynamic voltage management, power-up sequencing control and design flexibility.

LP3905 PMU
Available in 14-pin thermally enhanced LLP package measuring 4-by-4 mm, LP3905 PMU has two integrated 600mA high-efficiency buck regulators and two 150mA ultralow-noise linear regulators. The dual buck regulators have fixed and adjustable output voltage range from 1V to 3.3V with up to 90 percent efficiency.

The buck regulators of LP3905 feature intelligent automatic switching between PWM and PFM modes to achieve the highest efficiency possible for the entire load range. When in PWM mode, both regulators have a switching frequency of 2MHz, allowing the use of small external components. The dual linear regulators have an output voltage range of 1.5-3.3V, with low dropout voltage and low output voltage noise.

Both devices are available now. LP3906 is priced at $3.30 each and LP3905 is priced at $2.50 each in 1,000-unit quantities.