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AAT3172 参数 Datasheet PDF下载

AAT3172图片预览
型号: AAT3172
PDF下载: 下载PDF文件 查看货源
内容描述: 高电流LED闪光灯驱动器电荷泵IC [High Current LED Flash Driver Charge Pump IC]
分类和应用: 驱动器闪光灯
文件页数/大小: 15 页 / 450 K
品牌: AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
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AAT3172  
High Current LED Flash Driver Charge Pump IC  
C1  
C2  
1µF  
1µF  
C1+  
VIN  
C1- C2+  
C2-  
2.7V to 5.5V  
VOUT  
CIN  
4.7µF  
COUT  
2.2µF  
Flash  
LED  
AAT3172  
F1  
F2  
EN/SET  
EN/SET  
STAT1  
STAT2  
GND  
Figure 2: Flash Plus Status Lighting.  
the input supply directly to the output. The power  
conversion efficiency can be approximated by:  
LED Selection  
The AAT3172 is designed to drive high-intensity  
white LEDs. It is particularly suitable for LEDs with  
an operating forward-voltage in the range of 4.2V  
to 1.5V.  
VF · ILED VF  
η =  
VIN · IIN  
VIN  
The charge pump device can also drive other loads  
that have similar characteristics to white LEDs. For  
various load types, the AAT3172 provides a high-cur-  
rent, programmable ideal constant current source.  
Due to the very low 1X mode quiescent current, the  
input current nearly equals the current delivered to  
the LED. Further, the low-impedance bypass  
switch introduces negligible voltage drop from input  
to output.  
Device Power Efficiency  
The AAT3172 power conversion efficiency  
depends on the charge pump mode. By definition,  
device efficiency is expressed as the output power  
delivered to the LED divided by the total input  
power consumed.  
The AAT3172 further maintains optimized perform-  
ance and efficiency by detecting when the input  
voltage is not sufficient to sustain LED current. The  
device automatically switches to 1.5X mode when  
the input voltage drops too low in relation to the  
LED forward voltage.  
In 1.5X mode, the output voltage can be boosted to  
3/2 the input voltage. The 3/2 conversion ratio  
introduces a corresponding 1/2 increase in input  
current. For ideal conversion, the 1.5X mode effi-  
ciency is given by:  
POUT  
PIN  
η =  
When the input voltage is sufficiently greater than  
the LED forward voltage, the device optimizes effi-  
ciency by operating in 1X mode. In 1X mode, the  
device is working as a bypass switch and passing  
VF · ILED  
VF  
η =  
=
VIN · 1.5IIN 1.5 · VIN  
12  
3172.2006.05.1.5