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AAT2846 参数 Datasheet PDF下载

AAT2846图片预览
型号: AAT2846
PDF下载: 下载PDF文件 查看货源
内容描述: 高电流电荷泵,带有双LDO用于背光和闪光应用 [High Current Charge Pump with Dual LDO for Backlight and Flash Applications]
分类和应用:
文件页数/大小: 25 页 / 646 K
品牌: ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
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AAT2846  
High Current Charge Pump with Dual LDO  
for Backlight and Flash Applications  
Functional Block Diagram  
IN  
IN  
C1+  
OUTA  
FBA  
LDO A  
LDO B  
C1-  
1x/1.5x/2x  
Charge Pump  
C2+  
OUTB  
FBB  
C2-  
ENA  
ENB  
To LDO A  
To LDO B  
1.2V  
VREF  
REF  
OUT  
BL1  
BL2  
BL3  
BL4  
ENS  
FEN  
Control  
Logic  
BL5  
BL6  
CT  
FSET  
FL1  
FL2  
AGND PGND  
verter solutions. Each individual LED is driven by a  
current sink to AGND, allowing individual current  
control with high accuracy over a wide range of  
input voltages and LED forward voltages while  
maintaining high efficiency.  
Functional Description  
The AAT2846 is a highly integrated backlight and  
flash LED driver with two LDO linear regulators.  
The charge pump LED driver drives backlight and  
flash LEDs from a 2.7V to 5.5V input voltage. The  
LDO regulators are operated from the same input  
voltage range and produce regulated output volt-  
ages as low as 1.2V.  
The charge pump is controlled by the voltage across  
the LED current sinks. When any one of the active  
current sinks begins to dropout, the charge pump  
goes to the next higher mode (from 1X to 1.5X or  
from 1.5X to 2X mode) to maintain sufficient LED  
voltage for constant LED current. The AAT2846 con-  
tinuously monitors the LED forward voltages and  
uses the input voltage to determine when to reduce  
the charge pump mode for better efficiency. There is  
also a 500mV mode-transition hysteresis that pre-  
vents the charge pump from oscillating between  
charge pump modes.  
LED Drivers  
The LEDs are driven from an internal charge pump  
that, depending on the battery voltage and LED for-  
ward voltage, drives LEDs directly from the supply  
voltage (1X or bypass mode) or steps up the sup-  
ply voltage by a factor of 1.5 (1.5X mode) or 2 (2X  
mode). The charge pump requires only two tiny  
1µF ceramic capacitors, providing a more compact  
solution than typical inductor-based step-up con-  
The backlight and flash LED current levels are  
2
dynamically controllable by the AS Cwire single-wire  
2846.2007.08.1.0)  
11