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LED drivers add 1.33x pump mode

Posted: 10 Aug 2007 ?? ?Print Version ?Bookmark and Share

Keywords:charge pump-based LED drivers? charge pump? LEDs?

Leadis Technology Inc. has introduced the LDS8842 and LDS8830, its second and third product under a new family of charge pump-based LED drivers featuring a highly efficient 1.33x-mode enabled charge pump.

Targeted at mobile backlighting applications, the LDS8842 and the LDS8830 support up to four LEDs and three LEDs, with maximum current supply of 25mA and 32mA per channel, respectively.

In addition to the 1x/1.5x/2x charge pump modes traditionally offered, the LDS8842 and LDS8830 chips integrate an additional charge pump mode that generates an output voltage equal to 1.33 times the input voltage. Leadis' 1.33x pump mode serves as a higher-efficiency intermediate mode between the 1x and 1.5x modes, resulting in efficiency improvements of up to 10 percent over traditional offerings. Both the LDS8842 and LDS8830 are offered in a 3mm x 3mm package, with the LDS8830 being also available in a tiny 2.5mm x 2.5mm package.

"The higher efficiencies possible with our 1.33x technology provide customers with an additional means to increase battery life for their mobile offerings, enabling product differentiation and an enhanced consumer satisfaction," said Donato Montanari, vice president and general manager, LED drivers at Leadis Technology. "These devices are offered in extremely small packages that are suitable for today's compact cell phone designs, where real estate is at premium."

Key functions
LDS8842 is a high-efficiency 1x/1.33x/1.5x/2x fractional charge pump capable of driving up to four LEDs at up to 25mA each. LED dimming control is programmable with a one-wire interface enabling current level adjustment from 0.78mA to 25mA. LED channel matching is supported within 1.5 percent, with current accuracy at 2 percent.

The LDS8830 device is a high-efficiency 1x/1.33x/1.5x/2x fractional charge pump capable of driving up to three LEDs at up to 32mA each. LED dimming control is programmable with a one-wire interface enabling current level adjustment from 1mA to 32mA. LED channel matching is supported within 1.5 percent, with current accuracy at 2 percent.

Both devices offer input voltages from 2.5v to 5.5v are supported with efficiency up to 92 percent. Operation at switching frequencies of 1.3MHz (1.5x mode) and 1MHz (1.33x and 2x modes) enables low noise input ripple and utilization of small external ceramic capacitors. Other product features include soft start and current limiting, thermal shutdown and short circuit protection and a low current shutdown mode of 1?A max.

LDS8842 is offered in a 16-lead thin QFN 3mm x 3mm package with a maximum height of 0.8mm. LDS8830 is housedin a tiny 12-lead XQFN 2.5mm x 2.5mm with max height of 0.4mm or in a 16-lead TQFN or 12-lead TDFN 3mm x 3mm package with a max height of 0.8mm.




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