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AAT3103IJQ-4-T1 参数 Datasheet PDF下载

AAT3103IJQ-4-T1图片预览
型号: AAT3103IJQ-4-T1
PDF下载: 下载PDF文件 查看货源
内容描述: 3通道电荷泵LED驱动器 [3-Channel Charge-Pump LED Driver]
分类和应用: 驱动器
文件页数/大小: 17 页 / 1059 K
品牌: AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
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PRODUCT DATASHEET  
AAT3103  
ChargePumpTM  
3-Channel Charge-Pump LED Driver  
The ideal efficiency (η) in 1x charge-pump mode can be  
expressed as:  
Power Efficiency and Device Evaluation  
The charge pump efficiency discussion in the following  
sections accounts only for efficiency of the charge pump  
section itself. Due to the unique circuit architecture and  
design of the AAT3103, it is very difficult to measure  
efficiency in terms of a percent value comparing input  
power over output power.  
POUT VF · ILED VF · ILED VF  
η =  
=
=
PIN  
VIN · IIN VIN · IOUT VIN  
-or-  
VF  
VIN  
η (%) =  
· 100  
Since the AAT3103 outputs are pure constant current  
sources and typically drive individual loads, it is difficult  
to measure the output voltage for a given output pin to  
derive an overall output power measurement. For any  
given application, WLED forward voltage levels can dif-  
fer, yet the output drive current will be maintained as a  
constant.  
For a charge pump LED driver with VF of 3.2V and 4.2V  
input voltage, the theoretical efficiency is 76%. Due to  
internal switching losses and IC quiescent current con-  
sumption, the actual efficiency can be measured at 73%.  
This makes quantifying output power a difficult task  
when taken in the context of comparing to other WLED  
driver circuit topologies. A better way to quantify total  
device efficiency is to observe the total input power to  
the device for a given LED current drive level. The best  
WLED driver for a given application should be based on  
trade-offs of size, external component count, reliability,  
operating range, and total energy usage...not just %  
efficiency.  
2x Charge Pump Mode Efficiency  
The AAT3103 contains a charge pump which will boost  
the input supply voltage in the event where VIN is less  
than the voltage required to supply the output. The effi-  
ciency (η) can be simply defined as a linear voltage  
regulator with an effective output voltage that is equal  
to one half of the input voltage. Efficiency (η) for an  
ideal 2x charge pump can typically be expressed as the  
output power divided by the input power.  
The AAT3103 efficiency may be quantified under very  
specific conditions and is dependent upon the input volt-  
age versus the outputs of D1, D2 and D3 for a given  
constant current setting. Depending on the combination  
of VIN and voltages sensed at the current sources, the  
device will operate in load switch mode. When any one of  
the voltages sensed at the current sources nears drop-  
out, the device will operate in 2x charge pump mode.  
PF  
PIN  
η =  
In addition, with an ideal 2x charge pump, the output  
current may be expressed as 1/3 of the input current.  
The expression to define the ideal efficiency (η) can be  
rewritten as  
Each of these modes will yield different efficiency values.  
Refer to the following two sections for explanations for  
each operational mode.  
POUT VF · ILED  
=
VF · ILED  
VF  
η =  
=
PIN  
VIN · IIN VIN · 2 · IOUT 2 · VIN  
-or-  
1x Mode Efficiency  
VF  
2 · VIN  
The AAT3103 1x mode is operational at all times and  
functions alone to enhance device power conversion effi-  
ciency when VIN is higher than the voltage across the  
load. When in 1x mode, voltage conversion efficiency is  
defined as output power divided by input power.  
η (%) =  
· 100  
For a charge pump LED current source driver with VF of  
3.2V and 2.7V input voltage, the theoretical efficiency is  
59%. Due to internal switching losses and IC quiescent  
current consumption, the actual efficiency can be mea-  
sured at 57%. Efficiency will decrease substantially as  
load current drops below 1mA or when the voltage level  
PF  
PIN  
η =  
at VIN approaches the voltage level at VOUT  
.
w w w . a n a l o g i c t e c h . c o m  
12  
3103.2008.03.1.0