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ACT4082AUS-T 参数 Datasheet PDF下载

ACT4082AUS-T图片预览
型号: ACT4082AUS-T
PDF下载: 下载PDF文件 查看货源
内容描述: 16V , 1.2A , 1.4MHz的降压型DC / DC采用SOT23-6转换器 [16V, 1.2A, 1.4MHz Step-Down DC/DC Converter in SOT23-6]
分类和应用: 转换器
文件页数/大小: 11 页 / 420 K
品牌: ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
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ACT4082A  
Active- Semi  
Rev0, 16-May-08  
FUNCTIONAL BLOCK DIAGRAM  
IN  
CSA  
REGULATOR  
& UVLO  
EN  
BST  
CONTROL  
SOFT-START  
PWM Comparator  
ILIM Comparator  
HICCUP  
Q1  
DRIVER  
OSCILLATOR  
SW  
REFERENCE  
& THERMAL  
SHUTDOWN  
COMPENSATION  
EA  
FB  
G
in setting the ACT4082A's transient response and  
ensuring stability. For most applications, choosing  
RFB1 = 49.9kprovides good results. For applica-  
tions with output voltages of 1.8V or lower, use a  
larger RFB1 value such as 80.6k. Once RFB1 is  
FUNCTIONAL DESCRIPTION  
The ACT4082A is a current-mode step-down  
DC/DC converter that provides excellent transient  
response with no extra external compensation com-  
ponents. This device contains an internal, low-  
resistance, high-voltage power MOSFET, and oper-  
ates at a high 1.4MHz operating frequency to en-  
sure a compact, high-efficiency design with excel-  
lent AC and DC performance.  
chosen, use the following equation to choose RFB2  
:
RFB1  
RFB2  
=
(1)  
V
OUT  
1  
0.81V  
Selecting the Inductor  
Setting the Output Voltage  
The ACT4082A was optimized for use with a 4.7µH  
inductor. When choosing an inductor, choose one  
with a DC resistance of less than 250mand a DC  
current rating that is typically 30% higher than the  
maximum load current.  
An external voltage divider is used to set the output  
voltage, as well as provide a known impedance  
from VOUT to FB for compensation purposes. Con-  
nect a 50kresistor from the output to FB to ensure  
stable compensation, and select the bottom resistor  
to provide the desired regulation voltage.  
During typical operation, the inductor maintains a  
continuous current to output load. The inductor  
current has a ripple that is dependent on the  
inductance value.  
Figure 1:  
Output Voltage Setting  
Higher inductance reduces the peak-to-peak ripple  
current. The trade off for high inductance value is  
the increase in inductor core size and series  
resistance, and a reduction in current handling  
capability.  
VOUT  
ACT4082A  
RFB1  
FB  
RFB2  
If efficiency at light loads (such as less than 100mA)  
is critical in the application, a larger inductor is  
recommended.  
The feedback resistor (RFB1) interacts with the inter-  
nal compensation network, and plays an important  
Innovative PowerTM  
- 6 -  
www.active-semi.com  
Copyright © 2008 Active-Semi, Inc.