On Semi CAT3649六路四模式LED驱动方案
On Semi公司的CAT3649是具有32种调光亮度的六路四模式LED驱动器,提供4种电荷泵模式(1倍、1.33倍、1.5倍及2倍), 这种分数型电荷泵支持从2.4 V到5.5 V的宽输入电压范围。LED电流可以通过单线(1-wire)接口以32个线性增量的模拟调光来调节，也可以通过PWM作进一步的调节,广泛用于最新的智能手机及其它消费类手持应用，如数码相机和便携式媒体播放器(PMP)。本文介绍了CAT3649主要特性,功能方框图以及典型应用电路.
The CAT3649 is a high efficiency Quad−Modefractional charge pump that can drive up to six LEDs. The inclusion of a 1.33x fractional charge pump mode increases the device efficiency by up to 10% over traditional 1.5x charge pumps with no added external capacitors.
Low noise input ripple is achieved by operating at a constant switching frequency which allows the use of small external ceramic capacitors. The multi−fractional charge pump supports a wide range of input voltages from 2.4 V to 5.5 V.
The LED current can be adjusted in different ways. The full−scale LED current is set to 25 mA once the device is enabled. Analog dimming in 32 linear steps is achieved via a 1−wire pulse−dimming input (ADIM).
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