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AME5134AEVAADJZ-3 参数 Datasheet PDF下载

AME5134AEVAADJZ-3图片预览
型号: AME5134AEVAADJZ-3
PDF下载: 下载PDF文件 查看货源
内容描述: [Interface Circuit]
分类和应用:
文件页数/大小: 14 页 / 363 K
品牌: AME [ ANALOG MICROELECTRONICS ]
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AME, Inc.  
High-Efficiency, 30V Boost  
Converters for 2 to 6 White LEDs  
AME5134  
n Detailed Description  
The AME5134 features a minimum off-time, current-  
limited control scheme. Operation can be best under-  
stood by referring to Figure 2. When the voltage at the  
FB pin is less than regulation threshold,NMOS switch is  
turned on and the inductor current ramps up to the cur-  
rent limit. Once the current in the inductor reaches peak  
current limit theNMOS switch will be turned off for 250nS,  
at mean time the SW voltage will rise to a voltage that  
equals output voltage plus a diode drop and the inductor  
current will begin to decrease as shown in Figure 2. Dur-  
ing this time the energy stored in the inductor is trans-  
ferred to COUT and the load. After 250ns, if the voltage at  
FB is above the regulation threshold, the NMOS switch  
stays off. If the voltage at FB is below the regulation thresh-  
old, the NMOS switch turns back on and the cycle re-  
peats.  
Dimming Control  
A. Use a DC Signal to CTRL pin  
At CTRL, applying a DC signal in the range of 0V to  
1.8V control the LED current. CTRL can be overdriven;  
however, applying a CTRL greater than 1.8V does not in-  
crease the LED current above the level at 1.8V. ( See the  
LED Current vs. CTRL Voltage graph.)  
B. Use a PWM Signal to CTRL pin  
The CTRL input is used as a digital input allowing LED  
brightness control with a logic-level PWM signal applied  
directly to CTRL. The frequency range is from 100Hz to  
10kHz, while 0% duty cycle corresponds to minimum  
current, and 100% duty cycle corresponds to full current.  
(See the LED Current vs. CTRL Duty Cycle graph). The  
CTRL resistor and SS capacitor from a low pass filter, so  
PWM dimming results in DC current to the LEDs without  
the need for additional RC filters.  
Shutdown  
The AME5134 features a low-current shutdown fea-  
ture. When EN is low, the IC turns off, reducing its sup-  
ply current to approximately 0.1mA. For normal opera-  
tion, drive EN high or connect to VIN.  
Capacitor Selection  
A 0.47mF ceramic output capacitor (C2) is recom-  
mended for most applications. For circuits driving six or  
fewer LEDs, use a 4.7mF ceramic input capacitor (C1).  
For best stability over a wide temperature range, use  
capacitors with an X5R, X7R, or better dielectric.  
Soft-Start  
Soft-start provided on the AME5134 to minimize in-  
rush current. The soft-start time is set with an external  
capacitor, C3. Use the following equation to solve for C3:  
Inductor Selection  
TheAME5134 has a 220mA inductor current limit and  
can drive up to six LEDs at 20mA. The selected induc-  
tor must have a saturation current that meets the maxi-  
mum peak current of the converter. For best efficiency,  
the inductor's DC resistance should also be as low as  
possible.  
tss  
C3 =  
2 x 10 5  
Where tss is the soft-start time.  
Overvoltage Protection  
Diode Selection  
OVP is designed to prevent the output voltage from  
exceeding the maximum internal NMOS switch voltage  
rating of 30V. The peak output voltage in an overvoltage-  
protection event is set with a resistor-divider from the  
output connected to 0V (R1 and R2). Select a value for  
R2(10kW is recommended), then solve for R1 using the  
following equation:  
The AME5134 high switching frequency demands a  
high-speed rectification diode (D1) for optimum efficiency.  
A Schottky diode is recommended due to its fast recov-  
ery time and low forward-voltage drop.  
VOUT  
R1 = R2 x (  
1 )  
VOV  
Where VOV is the overvoltage threshold, and VOUT is the  
desired peak output voltage.  
Rev.C.01  
7
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