Although the scope of the Electronica event, held last week in Munich, Germany, broadly encompasses many areas of electronics, a number of power semiconductor vendors used this forum to unveil some of their latest discrete and IC products. In addition to offering new features and performance capabilities, these products highlight some of the ongoing industry trends in power MOSFETs, offline switching ICs, dc-dc converter ICs and LED drivers.
In the power MOSFET area, vendors continue to develop packaging alternatives to the popular SO-8. Some of the new packages offer a feature known as double-sided or top-side cooling. In packages with this feature, the thermal resistance from die to case has been decreased so that the device can dissipate heat efficiently through the top of the package with a heatsink attached, if desired.
At Electronica, Vishay Siliconix introduced its version of double-sided cooling, the PolarPAK. This package handles currents in excess of 60 A in an SO-8 footprint. Unlike similar-sized packages with double-sided cooling, PolarPAK bears a strong resemblance to a standard SO-8 in that it uses both a lead frame and plastic encapsulation. A cutout in the encapsulation on top of the package exposes a metal tab, which may be attached to an external heatsink. This approach provides excellent die protection, reliability and easy handling in manufacturing. Because footprint size and pad location are fixed, the company will be able to offer different sized die in this package, allowing customers to swap MOSFETs within the PolarPAK family without changing their board layouts.
Meanwhile, International Rectifier expanded its line of MOSFETs with double-sided cooling by introducing 100-V and 40-V MOSFETs in its DirectFET package. While earlier, low-voltage DirectFETs targeted VRM and motherboard dc-dc converter designs, these latest DirectFETs are aimed at 48-V networking, telecommunications and high-end computing systems. The company also released a full-bridge controller IC developed with bus converter applications in mind. The IR2086S controller simplifies implementation of dc-dc converters based on primary side full-bridge topologies.
Among the other chipmakers exhibiting at Electronica, two launched new versions of their offline power supply ICs. Fairchild Semiconductor released three new Green FPS integrated power switches that address power supply designs in the 100-W to 250-W range. Target applications include consumer equipment such as color TVs and DVD receivers. In addition to extending the power range addressed by its offline switching ICs, the latest devices satisfy the International Energy Agency’s 1 Watt Initiative aimed at reducing standby power losses to below 1 W.
Another vendor, Power Integrations Inc., has added members to its LinkSwitch offline IC family. The LinkSwitch-HF chips implement low-cost switching power supplies at low power levels for applications that require tight output regulation. Battery chargers and appliances that require fault protection are among the target applications for these devices. In LinkSwitch-HF, the switching frequency has been raised to 200 kHz, which allows very low flux density transformer designs and practically eliminates audible noise.
In the dc-dc converter area, National Semiconductor announced a family of dc-dc converter ICs optimized for powering RF power amplifiers (PAs) from a single Li-Ion battery. By addressing a previously unregulated section of the cell phone circuitry, the LM3200 step-down regulators will enable cell phone makers to reduce power consumption by up to 80%.
Among the other power ICs introduced at Electronica, several products were added to the ever-expanding universe of LED drivers developed to power white and color LEDs. These parts address backlighting requirements in cell phones and other portables, which increasingly feature multiple displays. Texas Instruments unveiled the TPS6106x family of synchronous boost converters that can power up to five series-connected white LEDs. These converters are offered in 1-mm x 1.5-mm chip-scale packages, making it possible to build very small inductor-based LED driver designs.
Advanced Analogic Technologies Inc. introduced five new tri-mode high-efficiency charge pumps for white LED backlight and color LED applications. Capable of driving four or six individual LEDs at up to 30 mA per channel, the AAT3151/2/3/6 products represent AnalogicTech’s first family of current sink LED drivers. These new tri-mode devices combine a load switch (1X) and a high-efficiency (1.5X or 2X) charge pump with an internal sensing circuit that monitors the required voltage on each constant current sink input. Another device, the AAT3129, is a high-efficiency charge pump that delivers a regulated current to red, green and blue LEDs via three internal switches.
National Semiconductor also introduced several LED drivers, which included a novel device that synchronizes lighting and audio in portable products. The LP3950 color LED driver with audio synchronizer enables the color LEDs on the phone or MP3 player to blink and change color in time with the device’s music or ring tones. The LP3950 synchronizes the LEDs based on the music’s amplitude or frequency response.
In addition to the LP3950, the company introduced the LP3942 color LED driver with charge pump and the LP3931 color LED driver with magnetic boost converter.