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ACT4065A 参数 Datasheet PDF下载

ACT4065A图片预览
型号: ACT4065A
PDF下载: 下载PDF文件 查看货源
内容描述: 高输入2A降压转换器 [High Input 2A Step Down Converter]
分类和应用: 转换器
文件页数/大小: 9 页 / 298 K
品牌: ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
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®
ACT4065A  
Rev 0, 23-Apr-12  
FUNCTIONAL BLOCK DIAGRAM  
is charged to VSW + 5V when the Low-Side Power  
Switch turns on.  
FUNCTIONAL DESCRIPTION  
As seen in, Functional Block Diagram, the AC-  
T4065A is a current mode pulse width modulation  
(PWM) converter. The converter operates as fol-  
lows:  
The COMP voltage is the integration of the error  
between the FB input and the internal 0.808V refer-  
ence. If FB is lower than the reference voltage,  
COMP tends to go higher to increase current to the  
output. Current limit happens when COMP reaches  
its maximum clamp value of 2.0V.  
A switching cycle starts when the rising edge of the  
Oscillator clock output causes the High-Side Power  
Switch to turn on and the Low-Side Power Switch to  
turn off. With the SW side of the inductor now con-  
nected to IN, the inductor current ramps up to store  
energy in its magnetic field. The inductor current  
level is measured by the Current Sense Amplifier  
and added to the Oscillator ramp signal. If the re-  
sulting summation is higher than the COMP volt-  
age, the output of the PWM Comparator goes high.  
When this happens or when Oscillator clock output  
goes low, the High-Side Power Switch turns off and  
the Low-Side Power Switch turns on. At this point,  
the SW side of the inductor swings to a diode volt-  
age below ground, causing the inductor current to  
decrease and magnetic energy to be transferred to  
the output. This state continues until the cycle starts  
again.  
The Oscillator normally switches at 210kHz. How-  
ever, if the FB voltage is less than 0.6V, then the  
switching frequency decreases until it reaches a  
minimum of 30kHz at VFB = 0.15V.  
Shutdown Control  
The ACT4065A has an enable input EN for turning  
the IC on or off. When EN is less than 0.7V, the IC  
is in 8μA low current shutdown mode . When EN is  
higher than 0.8V, the IC is in normal operation  
mode. EN is internally pulled up with a 4μA current  
source and can be left unconnected for always-on  
operation. EN should never be directly connected to  
IN.  
Thermal Shutdown  
The ACT4065A automatically turns off when its  
junction temperature exceeds 155°C.  
The High-Side Power Switch is driven by logic us-  
ing the BS bootstrap pin as the positive rail. This pin  
Innovative PowerTM  
- 4 -  
www.active-semi.com  
Copyright © 2012 Active-Semi, Inc.