POWER AND LINEAR IC SOLUTIONS

Simple, Flexible, Low Noise RGB LED Driver

Many designers face a dilemma when deciding how to backlight LCD panels or displays. Should they use white LEDs or an RGB light source that has a purer white light? Both solutions offer advantages. One specific RGB-based solution is Linear Technology’s LTC3212, an inductorless low noise LED driver IC designed to drive low profile RGB LEDs in portable electronic device displays and lighting applications.

The LTC3212 is capable of driving three LEDs at up to 25mA each from a wide input voltage range of 2.7V to 5.5V and is optimised for single cell Li-Ion/Polymer battery applications. The LTC3212 achieves simplicity and flexibility via a single wire On/Off interface and three individual resistor-programmable LED current sources to control dimming and brightness. White mode optimises the red, green and blue LED current ratios for optimal white colour when all three RGB LEDs are programmed On. Quiescent current in standby mode is only 400µA, maximising battery run time.



The LTC3212’s multimode charge pump features low noise, constant frequency operation to minimise ripple and the device’s automatic mode switching optimises efficiency. The LTC3212 powers up in 1x mode and when dropout is detected at any LED enables the charge pump in doubler (2x) mode. Internal soft-start circuitry prevents inrush current shutdown; circuit protection and thermal shutdown provide extra operational safety for both the IC and the LEDs. Typical applications include highly space-constrained portable electronic devices such as cellular phone and media player displays, in addition to keypad lighting and RGB LED backlighting.

The LTC3212 is available in the low profile (0.75mm) 12-lead DFN (2mm x 3mm) package. The device requires only three small capacitors and one to three programming resistors to create a tiny, complete RGB or white LED current controller and power supply solution.

Low to Medium Power Multi-Display LED Drivers - Inductorless

Part Number	Conversion Ratio	Max. Total LED Current (mA)	Number of Displays and Display Type	Max. # of White LEDs
LTC3212	1x/2x	75	3 (RGB)	3****
LTC3219	1x/1.5x/2x	250	3 (Main, SUB, RGB)	9***
LTC3206	1x/1.5x	400	3 (Main, SUB, RGB)	4+2+3
LTC3210/-1	1x/1.5x/2x	500	2 (Main, CAM)	4+1**
LTC3209-1	1x/1.5x/2x	600	3 (Main, CAM, Aux)	6+1**+1
LTC3209-2	1x/1.5x/2x	600	3 (Main, CAM, Aux)	5+2**+1
LTC3207	1x/1.5x/2x	600	4 (Main, SUB, CAM, RGB)	12***+1**
LTD3208	1x/1.5x/2x	1000	5 (Main, SUB, CAM, RGB, Aux)	4+2+4+3+4

** High Current LED, *** Universally Configurable, **** R, G, B LEDs

Features

• Power and current control for driving RGB or white LEDs
• Three individually programmable current sources
• 25mA/LED maximum LED current
• 1x or 2x mode, low noise, constant frequency charge pump
• Single-wire enable control for all LEDs
• White mode optimises R, G, B currents for white light
• 2.7V to 5.5V input voltage range optimised for Li-Ion/Polymer applications
• Automatic soft start, mode switching and disconnect in shutdown mode
• Tiny, low profile 2mm x 3mm x 0.75mm DFN-12 package

For further information, including the LTC3212 Datasheet, please click here