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AAT3114 参数 Datasheet PDF下载

AAT3114图片预览
型号: AAT3114
PDF下载: 下载PDF文件 查看货源
内容描述: 高能效1.5x分数电荷泵为白光LED应用 [High Efficiency 1.5X Fractional Charge Pumps For White LED Applications]
分类和应用:
文件页数/大小: 15 页 / 1591 K
品牌: ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
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PRODUCT DATASHEET  
AAT3113,AAT3114/14A  
TM  
ChargePump  
High Efficiency 1.5X Fractional Charge Pumps For White LED Applications  
tHI  
tOFF  
tLO  
EN/SET  
Code  
OFF  
OFF  
1
2
3
Figure 2: EN/SET Timing Diagram.  
T
HI > 50ns  
300ns < TLO < 75µs  
50ns minimum to enable  
OFF  
n
ON/1  
2
3
4
5
6
(n < =32)  
Figure 3: Enable / Disable / LED Brightness Level Set Data Input.  
internal switching losses and IC quiescent current con-  
LED Selection  
sumption, the actual efficiency can be measured at 93%.  
These figures are in close agreement for output load con-  
ditions from 1mA to 100mA. Efficiency will decrease as  
load current drops below 0.05mA or when the level of VIN  
approaches VOUT. Refer to the Typical Characteristics sec-  
tion of this datasheet for measured plots of efficiency  
versus input voltage and output load current for the  
given charge pump output voltage options.  
AAT3113 and AAT3114/14A devices are designed to drive  
white LEDs with forward voltages to 4.2V. Since the  
D1:D6 output current sources are matched with negligi-  
ble voltage dependence, the LED brightness will be  
matched regardless of their forward voltage matching.  
Charge Pump Efficiency  
The AAT3113 and AAT3114/14A devices are fractional  
charge pumps. The efficiency (η) can be simply defined  
as a linear voltage regulator with an effective output  
voltage that is equal to one and one half times the input  
voltage. Efficiency (η) for an ideal 1.5X charge pump can  
typically be expressed as the output power divided by  
the input power:  
Power Efficiency and Device Evaluation  
The charge pump efficiency discussion in the previous sec-  
tion only accounts for efficiency of the charge pump sec-  
tion itself. Due to the unique circuit architecture and  
design of the AAT3113 and AAT3114/14A, it is very diffi-  
cult to measure efficiency in terms of a percent value  
comparing input power over output power. Since the  
device outputs are pure constant current sources, it is dif-  
ficult to measure the output voltage for a given output (D1  
to D6) to derive an output power measurement. For any  
given application, white LED forward voltage levels can  
differ, yet the output drive current will be maintained as a  
constant. This makes quantifying output power a difficult  
task when taken in the context of comparing to other  
white LED driver circuit topologies. A better way to quan-  
tify total device efficiency is to observe the total input  
power to the device for a given LED current drive level.  
The best white LED driver for a given application should  
be based on trade-offs of size, external components  
count, reliability, operating range, and total energy  
usage...not just “% efficiency.”  
POUT  
η =  
PIN  
In addition, with an ideal 1.5X charge pump, the output  
current may be expressed as 2/3 of the input current.  
The expression to define the ideal efficiency (η) can be  
rewritten as:  
POUT  
PIN  
VOUT · IOUT  
VOUT  
η =  
=
=
VIN · 1.5IOUT 1.5VIN  
-or-  
VOUT  
η(%) = 100  
1.5V  
IN  
For a charge pump with an output of 5V and a nominal  
input of 3.5V, the theoretical efficiency is 95%. Due to  
w w w . a n a l o g i c t e c h . c o m  
10  
3113.2008.05.1.10