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Negative charge offers optimized light management

Posted: 22 Jun 2007 ?? ?Print Version ?Bookmark and Share

Keywords:negative charge pump? LCD display backlights?

Maxim Integrated Products introduces the MAX8647, a negative charge pump that provides the industry's highest efficiency in powering LCD display backlights.

MAX8647 achieves a significant 12 percent boost in efficiency, even with large LED forward-voltage mismatch, said Maxim.

'Power'-ful solution
MAX8647's negative charge-pump architecture eliminates in-line resistance from battery to LEDs. As a result, mode switching from 1x to 1.5x is delayed during battery discharge. The adaptive-mode switching technology supplies, dims, and regulates each LED individually. The net result of this innovative technology is a 12 percent increase in LED efficiency.

The additional efficiency extends battery life. This extra efficiency is especially important for cell phones, where backlight is a major power-consuming function. Greater system efficiency leads to proportionally longer talk-time. Moreover, a smaller battery can achieve the same talk-time, so the manufacturer will reduce costs. MAX8647 can also replace the inductor-boost LED drivers which consume a large piece of PCB estate in conventional designs.

MAX8647's applications extend beyond complex handheld devices to any display backlights and general light management. An I?C interface controls each LED that enables multizone, "fun" light management for up to 32 brightness levels, or 32,768 colors with RGB LEDs.

The low 70?A quiescent current and the 100?A (min) dimming current facilitate "always-on" TFT displays that require minimal power. Highly accurate, 1 percent current accuracy draws minimum battery current for each LED's required brightness. MAX8647 also features temperature derating and overvoltage protection to extend the life of the LEDs.

A sister product to the MAX8647, the MAX8648 negative charge pump also has adaptive-mode switching to each LED. The MAX8648 groups the control of the LEDs into three zones with serial-pulse dimming.

The MAX8647/8648 are available in a tiny 16-pin TQFN (3-by-3-by-0.8mm). They operate under the ?40C to 85C extended temperature range.

An evaluation kit (MAX8648 EV Kit) is available to speed design. Prices start at $1.95 for the MAX8647, and $1.70 for the MAX8648 for 2,500-unit quantities.

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