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A7116E5VR-18 参数 Datasheet PDF下载

A7116E5VR-18图片预览
型号: A7116E5VR-18
PDF下载: 下载PDF文件 查看货源
内容描述: [DC-DC CONVERTER/ BUCK]
分类和应用: DC-DC转换器
文件页数/大小: 14 页 / 433 K
品牌: AITSEMI [ AiT Semiconductor ]
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A7116  
AiT Semiconductor Inc.  
www.ait-ic.com  
DC-DC CONVERTER/ BUCK (STEP-DOWN)  
1.5MHz, 700mA SYNCHRONOUS WITH LOW QUIESCENT CURRENT  
Dropout Operation  
When the input voltage decreases toward the value of the output voltage, the A7116 allows the main switch to  
(Note 6)  
remain on for more than one switching cycle and increases the duty cycle  
until it reaches 100% The  
output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. At  
low input supply voltage, the RDS(ON) of the P-Channel MOSFET increases, and the efficiency of the converter  
decreases. Caution must be exercised to ensure the heat dissipated not to exceed the maximum junction  
temperature of the IC.  
Note 6: The duty cycle D of a step-down converter is defined as:  
V OUT  
D = TON × fOSC ×100% ≈  
×100%  
VIN  
Where TON is the main switch on time and fOSC is the oscillator frequency (1.5MHz).  
Maximum Load Current  
The A7116 will operate with input supply voltage as low as 2.5V, however, the maximum load current  
decreases at lower input due to large IR drop on the main switch and synchronous rectifier. The slope  
compensation signal reduces the peak inductor current as a function of the duty cycle to prevent  
sub-harmonic oscillations at duty cycles greater than 50%. Conversely the current limit increases as the  
duty cycle decreases.  
Layout Guidance  
When laying out the PCB board, the following suggestions should be taken to ensure proper operation of the  
A7116. These items are also illustrated graphically in Figure 2 & Figure 3.  
1. The power traces, including the GND trace, the SW trace and the VIN trace should be kept short, direct  
and wide.  
2. The VFB pin should be connected directly to the feedback resistor. The resistive divider R1/R2 must be  
connected between the (+) plate of Cout and ground.  
3. Connect the (+) plate of C1 to the VIN pin as closely as possible. This capacitor provides the AC current  
to internal power MOSFET.  
4. Keep the switching node, SW, away from the sensitive VFB node.  
5. Keep the (-) plates of C1 and C3 as close as possible.  
REV1.2  
- JAN 2009 RELEASED, MAY 2016 UPDATED -  
- 9 -