Catalyst公司的CAT3647/3648是3/4路电荷泵,具有超高效率,能驱动3或4个并联的LED,每个LED的输出电流都可高度匹配.LED的电流和调光控制(有31档)通过1线的数字接口完成. CAT3647/3648的输入电压从2.5V到5.5V,有四种电荷泵模式: 1x, 1.33x, 1.5x和2x, 效率高达92%,可广泛应用在LCD显示器背光,手机,数码相机和手持设备.本文介绍了CAT3647/3648的主要性能, 功能方框图, 典型应用电路以及评估板的电路图和所用的元器件列表.
The CAT3648 is a high efficiency quad-mode fractional charge pump that can drive up to four LEDs programmable by a one wire digital interface.The inclusion of a 1.33x fractional charge pump mode increases 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 2.5V to 5.5V.
The EN/DIM logic input functions as a chip enable and a digital dimming interface for setting the current in all LED channels. The 1-wire pulse-dimming interface supports 32 linear steps from full-scale down to zero current.
The device is available in the tiny 16-pad TQFN 3mm x 3mm package with a max height of 0.8mm.
CAT3648主要特性:
High efficiency 1.33x charge pump
Quad-mode charge pump: 1x, 1.33x, 1.5x, 2x
Drives up to 4 LEDs at 25mA each
1-wire EZDim™ 32 linear steps
Power efficiency up to 92%
Low noise input ripple in all modes
“Zero” current shutdown mode
Soft start and current limiting
Short circuit protection
Thermal shutdown protection
3mm x 3mm, 16-pad TQFN package
CAT3648应用:
LCD Display Backlight
Cellular Phones
Digital Still Cameras
Handheld Devices
图1. CAT3648典型应用电路
图2.CAT3648功能方框图
图3.驱动3个LED的CAT3648应用电路
图4.CAT3648演示/评估板外形图
图5.CAT3647/3648评估板电路图
下表为CAT3647/3648评估板元件列表
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