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ACT6305_12 参数 Datasheet PDF下载

ACT6305_12图片预览
型号: ACT6305_12
PDF下载: 下载PDF文件 查看货源
内容描述: 低投入高效率同步升压型DC / DC转换器 [Low Input High Efficiency Synchronous Step-Up DC/DC Converter]
分类和应用: 转换器
文件页数/大小: 9 页 / 390 K
品牌: ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
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ACT6305  
Rev 3, 15-Nov-12  
FUNCTIONAL BLOCK DIAGRAM  
OUT  
LOW INPUT  
START UP  
EN  
REFERENCE  
VREF  
1µs  
ONE -SHOT  
SET  
LATCH Q  
RESET  
5µs  
ONE -SHOT  
DRIVER  
LX  
+
VREF  
ERROR  
COMPARATOR  
FEEDBACK  
SELECT  
+
FB  
CURRENT LIMIT  
COMPARATOR  
G
Light Load Operation  
FUNCTIONAL DESCRIPTION  
Under light load conditions, the IC automatically  
enters a power-saving mode by extending the OFF  
time. This reduces switching losses and allows the  
ACT6305 to maintain high efficiency across a very  
wide load range.  
As seen in the Functional Block Diagram, the  
ACT6305 comprises a reference, low input startup  
circuitry, feedback select, error comparator, control  
logic and timers, internal power MOSFETs and cur-  
rent comparators.  
Low Voltage Startup  
Main Control Loop  
The ACT6305 uses proprietary start-up circuitry that  
allows it to achieve very low voltage startup down to  
1V. The ACT6305 remains in low voltage startup  
mode until VOUT exceeds 1.85V. The ACT6305 can-  
not support its full rated load current when operat-  
ing in low-voltage startup mode. Care should be  
taken to minimize load current during startup.  
The ACT6305 control architecture utilizes a series  
of one-shot and current sense circuits to regulate  
the output voltage with a very low quiescent supply  
current of just 17µA. An ON cycle begins when FB  
falls below the ACT6305’s internal reference volt-  
age. During an ON cycle, the N-channel power  
switch is turned on to connect the LX node to  
ground, transferring energy from input supply to the  
inductor. The ON cycle persists or the 1A current  
limit is reached. When either of these conditions  
occurs, the N-channel power switch turns off and  
the OFF cycle begins. During the OFF cycle, the  
energy stored in the inductor is released into the  
output capacitor and load through the synchronous  
rectifier. Once the 1µs minimum OFF time expires,  
another ON cycle begins when the FB voltage  
drops below the reference voltage.  
Shutdown  
In shutdown mode, all internal circuits including the  
power switch and the synchronous rectifier are dis-  
abled, reducing quiescent supply current to less  
than 1µA. Note that in shutdown mode, a DC path  
from the input supply to the output still exists due to  
the body diode of the synchronous rectifier.  
Innovative PowerTM  
- 7 -  
www.active-semi.com  
Copyright © 2012 Active-Semi, Inc.