LTC3219: 250mA Universal Cell Phone LED Drives 9 LEDs With Low Noise and 91% Efficiency
Linear Technology Corporation has announced the LTC3219, an inductorless, low noise, high efficiency LED driver for cell phone displays and lighting. The IC provides nine individually configurable current sources for Main, Sub and RGB displays.
Display currents are set via a precision internal current reference. The universal current sources can be digitally controlled with independent dimming, brightness, blinking, and gradation control, programmable via a simple two-wire I2C serial interface. The LTC3219’s 2.9V to 5.5V input voltage range has been optimized for single cell Li-Ion/Polymer battery applications. Efficiencies when driven from a Lithium battery (3.6V nominal) reach 91% with a quiescent current of only 400uA, maximizing battery run-time. Slew-rate limited switching reduces conducted and radiated noise (EMI).
The LTC3219’s multimode charge pump features low-noise constant-frequency operation, automatically optimizing efficiency based on the voltages across the LED current sources. The device powers up in 1x mode and automatically switches to boost mode (1.5x) when any enabled LED current source approaches dropout; a subsequent dropout switches the device into doubler (2x) mode.
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