Power chip drives up to eight white LEDs

A Marktech Optoelectronics product story

Edited by the Electronicstalk editorial team Apr 4, 2006

A compact DC/DC convertor IC powers multisegment white LEDs used to backlight new larger, colour LCD panels in small portable devices.

Marktech has expanded its Toshiba constant-current white LED driver product line with a compact DC/DC convertor IC for powering multisegment white LEDs used to backlight new larger, colour LCD panels in small portable devices such as cellphones and PDAs.

The high-precision high-performance TB62752AFUG white LED driver IC allows designers to save space and reduce component count by using a single device to drive from two to eight LEDs in series.

High output power allows for up to 800mW LED loading, while built-in protection functionality, including a dedicated surge-detection pin, further minimises the need for external components.

Suitable for use with portable designs based on Li-ion batteries, the TB62752AFUG operates with input voltages from 2.8 to 5.5V and achieves high power efficiency in excess of 80% during seven segment white LED operation.

Current precision is guaranteed to within +/-5% to ensure uniform LED lighting.

Surge detection voltage is rated at 37V.

Integrated protection functionality is designed to accommodate open and shorted LED failure modes without additional components.

In the case of an LED open circuit failure, the IC clamps the output voltage to a nondangerous level for the output transistor.

No current will flow through the LEDs and the IC remains undamaged.

This operation eliminates the need for Zener diodes traditionally used for such protection.

Should an LED short circuit failure occur, the TB62752AFUG ensures that the same current flows through the LED series configuration, with the result that all LEDs, except the failed part, continue to operate.

Toshiba's device is based on a BiCD 0.6um process that combines high withstand voltage, high current capacity double diffused MOS (DMOS) technology with high current drive bipolar transistors and CMOS FETs for low power consumption and high integration.

Withstand voltage for the part is rated at 40V.

Supplied in a SOT23-6 package, the TB62752AFUG has dimensions of just 2.9 x 2.8 x 1.3mm, including lead length.

Pricing for the TB62752AFUG driver starts at $0.67 in 5000-unit lots depending on package.