Review

Although a myriad of semiconductors targeting portable products in a wide range of categories entered the market in 2003, the majority were in the realm of power and display management. In addition to their primary functions, battery charging, providing USB power, backlighting, etc., power consumption, size, efficiency, and integration were equally critical considerations. Here are a sampling of the past year's offerings.

Available in a SOT-23-6 package, Seiko Instruments' (sii-ic.com) S-8941xA series CMOS, single mid-band op amps touted lower drive voltages and current consumption than existing bipolar op-amps. I/O voltages range from 1.2V to 5.5V, and input offset voltage ranges down to 5 mV maximum for the S-89411A and 10 mV maximum for the S-89410A. Both amps have a quiescent current of 135 µA at 1.2V and a current consumption of 0.1 µA in shutdown.

Linear Technology's (linear.com) LTC4052 standalone, pulse charger for single-cell Li-Ion/Li-Pol batteries turned down the heat with a power dissipation of 280 mW while fast charging at 0.8A from a 5.2V input source. This figure was reported as being 94% less than similar chargers dissipating up to 1.8W typical.

Measuring 3 mm x 3 mm, Texas Instruments' (ti.com) three bqTINY-II series ICs debuted as the industry's smallest, most integrated single-cell Li-Ion and Li-Pol battery chargers. Allowing portable products to be charged from an ac adapter or USB port, each device provides current sense, 4.2V regulation, and charge enable. They also include temperature sense, an ac-present indicator, and timer and termination enable depending on the chip.

At 94%, the SP6648 boost regulator from Sipex (ti.com) reported the highest efficiency available. The battery-friendly device in a 10-pin MSOP consumes a quiescent current of 12 µA while delivering up to 400 mA of output current. Other features include a 3.3V fixed output and a 2.5V to 5V adjustable output range plus programmable peak current.

Introduced as the market's first devices to make dual-role transceivers USB on the go (OTG) compliant, the MAX3353E and MAX3355E from Maxim Integrated Products (maxim-ic.com)) provide the 5V VBUS power and support dual-role controllers. Both devices provide ID detection for default host and peripheral assignment and feature a shutdown mode current of 0.4 µA.

In terms of integration, Fairchild Semiconductor (fairchildsemi.com) paired the FAN56XX LED driver ICs with the QTLP6XX series low-forward-voltage, surface-mount LEDs in a single package. According to the company, matching driver and LED characteristics yields very even brightness and color matching while allowing the LEDs to run directly from the battery without additional boost. Another mating scheme, Durel's (durel.com) D368 driver combines an electroluminescent lamp driver for backlighting monochrome displays and keypads with a high-brightness LED driver for color displays. The device, in a leadless PLLP-16 package, promises to accelerate design times and to save board space.

Focussing on power consumption and size, On Semiconductor's (onsemi.com) NLSF595 eight-segment, tri-color LED driver exhibits a static supply current of less than 1 µA at 25°C typical while occupying 3 mm x 3 mm of board space. The FPD94128 controller/column driver and FPD93140 power supply/gate driver from National Semiconductor (national.com) integrates a unique image-dependant backlight controller. This controller reduces backlight intensity when necessary, cutting the typical backlight power of 150 mW by 50% or more.

—Mat Dirjish

Outlook

Evolution
It's obvious that device size will always be a challenge when it comes to portables, especially since designers always seem to cram greater functionality into tighter quarters. Where these devices will go in terms of power management and usage will depend on the evolution of the semiconductors, passive components, and interfaces they'll be required to work with.

It wouldn't be surprising to see some hand-held products using a solar-power scheme in the near future. Possibly, a topology whereby the solar panel powers the unit when in use and charges the battery when idle, eliminating the external charger. Battery power would only be required during the absence of sufficient light. Initial candidates for this approach could be cell phones. Based on events of this past summer, this feature would come in quite handy during a blackout.

—MD