Toshiba Launches Charge Pump White LED Driver With Constant Current Regulator Targeted at Portable LCD Backlighting and Keypad Illumination Applications
(press release) - USA
Thursday April 21, 9:30 am ET
- New Device Provides Stable, Accurate Output Current and Up to 90 Percent Power-Efficiency in a Small Package

SAN JOSE, Calif., April 21 /PRNewswire/ -- Toshiba America Electronic Components, Inc. (TAEC)* today announced a new charge pump DC/DC converter IC that drives the white light-emitting diodes (LEDs) used to backlight liquid- crystal display (LCD) panels and illuminate keypads in portable devices such as cell phones, PDAs, MP3 players and digital cameras. Specially designed for constant current driving, TCA62735FLG can drive up to four white LEDs with uniform brightness. Mass production is scheduled to start this month with a monthly production volume of three million units.

"A wide range of portable applications from cell phones to MP3 players increasingly use white LEDs for LCD panel backlighting and keypad illumination. In response, Toshiba Corporation engineered the TCA62735FLG white LED driver to provide an efficient solution in electrical performance with constant current output for up to four white LEDs," said Andrew Burt, director of the Wireless Business Unit at TAEC. "The optimized design minimizes total circuit size, contributing to the portable equipment's small form factor."

The TCA62735FLG incorporates a power circuit and 4-channel fixed current output in a single chip and can drive fixed current to a total of four white LEDs, one for each output. It has a total output current capacity of greater than 120 milliamperes (mA) across all four channels. It achieves high- precision current regulation of 2.5 percent between the four channels and all four white LEDs attain identical brightness. Since TCA62735FLG monitors the power supply voltage and output pin voltage, it automatically switches the optimum step-up scaling factor in the LED load from 1.5 times to 2 times. Toshiba designed this device to minimize the efficiency degradation resulting from power supply voltage fluctuations, which was a weakness of older generation charge pump DC/DC converters. The switching frequency of 1 megahertz (MHz) makes it possible to select a small external component. The TCA62735FLG is housed in a space-saving 4mm X 4mm standard QFN16 package.

Main Features

* Has an output current capacity that supports power supply voltage
of 2.8 to 5.5 volts (V) and can provide more than 120mA to a total
of four channels

* Features on-chip fixed current output with standard current precision
of 2.5 percent between outputs; configurable with a single external
resistor

* Provides a built-in, over-output voltage protection circuit

* Provides a built-in soft start function

* Has shutdown consumption current of 1 microampere maximum
(rated 0 typical)

* Achieves power-efficiency of 70 percent or greater (rated at a power
supply voltage of 3.6V, output current of 120mA and white LED forward
voltage of 3.6V)

* Achieves power-efficiency of 90 percent or greater (rated at a power
supply voltage of 3.6V, output current of 80mA and white LED forward
voltage of 3.2V)

Development Background

Previous product generations of charge pump type DC/DC converters that only output voltage were characterized by wildly changing LED current values due to fluctuating white LED forward voltage drop (Vf). As well, these devices had difficulty achieving uniform brightness. When the relative ratio between the output voltage and white LED Vf was not suitable, reduced efficiency resulted. By employing a constant current driver, this new product can provide uniform brightness across all four LEDs. Since it automatically switches the optimum step-up scaling factor, it can attain high efficiency in lighting the white LEDs.

Pricing and Availability

Samples are currently available and volume production is scheduled to begin this month. Pricing is $0.96 each in 1,000-piece quantities. An evaluation kit to speed designs is also available. They are available from Toshiba directly or through TAEC's VAR, Marktech Optoelectronics (www.marktechopto.com).

Key Specifications

|---------------------|-------------------------------------------------|
| Process | CMOS-HV 0.6 micron |
|---------------------|-------------------------------------------------|
| Function | White LED Driving Charge Pump Type |
| | DC/DC converter |
|---------------------|-------------------------------------------------|
| Power Supply | 2.8V-5.5V |
| Voltage | |
|---------------------|-------------------------------------------------|
| Output Rating | 30mA per channel, total of 120mA |
|---------------------|-------------------------------------------------|
| Switching Frequency | 1MHz (typical) |
|---------------------|-------------------------------------------------|
| Package Dimensions | 4.0mm deep x 4.0mm wide x 0.85mm high (typical) |
|---------------------|-------------------------------------------------|

*About TAEC

Combining quality and flexibility with design engineering expertise, TAEC brings a breadth of advanced, next-generation technologies to its customers. This broad offering includes semiconductors, flash memory-based storage solutions, and displays for the computing, wireless, networking, automotive and digital consumer markets.

TAEC is an independent operating company owned by Toshiba America, Inc., a subsidiary of Toshiba Corporation, one of the five largest semiconductor companies worldwide in terms of global sales for the year 2003 according to Gartner/Dataquest's Worldwide Semiconductor Market Share Ranking. Toshiba is a world leader in high-technology products with more than 300 major subsidiaries and affiliates worldwide. For additional company and product information, please visit TAEC's website at chips.toshiba.com. For technical inquiries, please e-mail

Information in this press release, including product pricing and specifications, content of services and contact information, is current and believed to be accurate on the date of the announcement, but is subject to change without prior notice. Technical and application information contained here is subject to the most recent applicable Toshiba product specifications. In developing designs, please ensure that Toshiba products are used within specified operating ranges as set forth in the most recent Toshiba product specifications and the information set forth in Toshiba's "Handling Guide for Semiconductor Devices," or "Toshiba Semiconductor Reliability Handbook." This information is available at www.chips.toshiba.com, or from your TAEC representative.

All trademarks and tradenames used herein are the properties of their respective holders.

Source: Toshiba America Electronic Components, Inc.

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