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| 型号： | A8510GECTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 26/33页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR BCKLGHT/WHT 26QFN-EC |
| 标准包装： | 1 |
| 拓扑： | PWM，升压（升压） |
| 输出数： | 8 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 600kHz ~ 2.25MHz |
| 电源电压： | 5 V ~ 40 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 26-WFQFN 裸露焊盘 |
| 供应商设备封装： | 26-QFN/MLP-EP（4x4） |
| 包装： | 标准包装 |
| 工作温度： | -40°C ~ 105°C |
| 其它名称： | 620-1385-6 |
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A8510
Wide Input Voltage Range, High Efficiency
Fault Tolerant LED Driver
Step 5 Determining the resistor value for a particular switching
Corresponding capacitors include:
frequency. Use the R FSET values shown in figure 6. For example,
a 25.5 k Ω resistor will result in an 800 kHz switching frequency.
Step 6 Choosing the proper switching diode. The switching
diode must be chosen for three characteristics when it is used in
Vendor
Murata
Murata
Value
4.7 μ F 50 V
2.2 μ F 50 V
Part number
GRM32ER71H475KA88L
GRM31CR71H225KA88L
LED lighting circuitry. The most obvious two are: current rating
of the diode and reverse voltage rating.
The reverse voltage rating should be such that during operation
The rms current through the capacitor is given by:
? I Lused
I IN (max) 12
condition, the voltage rating of the device is larger than the maxi-
mum output voltage. In this case it is V OUT(OVP) .
The peak current through the diode is calculated as:
I COUT rms = I OUT
D (max) +
1 – D (max)
(24)
0.763 +
? I Lused
C IN =
? V IN
= 0.68 μ F
=
I dp = I IN (max) + 1 / 2 Δ I Lused (22)
= 1.483 A + 0.217 A = 1.70 A
The third major component in deciding the switching diode is the
reverse current, I R , characteristic of the diode. This characteristic
is especially important when PWM dimming is implemented.
During PWM off-time the boost converter is not switching. This
results in a slow bleeding off of the output voltage, due to leakage
currents. I R can be a large contributor, especially at high tempera-
tures. On the diode that was selected in this design, the current
varies between 1 and 100 μ A.
Step 7 Choosing the output capacitors. The output capacitors
must be chosen such that they can provide filtering for both the
boost converter and for the PWM dimming function. The big-
gest factors that contribute to the size of the output capacitor are
PWM dimming frequency and PWM duty cycle. Another major
contributor is leakage current ( I LK ). This current is the combina-
tion of the OVP leakage current as well as the reverse current of
the switching diode. In this design the PWM dimming frequency
0.434 A
= 0.320 A 1.48 A 12 = 0.583 A
1 – 0.763
The output capacitor must have a current rating of at least
583 mA. The capacitors selected in this design have a combined
rms current rating of 3 A.
Step 8 Selecting input capacitor. The input capacitor must be
selected such that it provides a good filtering of the input voltage
waveform. A good rule of thumb is to set the input voltage ripple
Δ V IN to be 1% of the minimum input voltage. The minimum
input capacitor requirements are as follows:
(25)
8 f SW
0.434 A
8 800 kHz 0.1 V
1 – D (min)
C OUT = I LK
f PWM(dimming)
= 200 μ A
= 3.96 μ F
I OUT ×
I IN rms =
0.320 A × 0.434 A
is 200 Hz and the minimum duty cycle is 1%.Typically the volt-
age variation on the output (V COUT ) during PWM dimming must
be less than 250 mV, so that no audible hum can be heard. The
capacitance can be calculated as follows:
(23)
V COUT
1 – 0.01
200 Hz 0.250 V
A capacitor larger than 3.96 μ F should be selected due to degra-
dation of capacitance at high voltages on the capacitor. A ceramic
4.7 μ F 50 V capacitor is a good choice to fulfill this requirement.
The rms current through the capacitor is given by:
? I Lused
I IN (max)
(1 – D (max)) 12
1.48 A
= = 0.11 A
(1 – 0.763) 12
A good ceramic input capacitor with ratings of 2.2 μ F 50V or
4.7 μ F 50 V will suffice for this application.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
(26)
26
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| A8511 | 制造商:ROCKWE 功能描述: |
| A8511KLPTR-T | 功能描述:IC LED DVR 150MA AUTO 28-TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 特色产品:LM3445 TRIAC Dimmable LED Driver 标准包装:55 系列:PowerWise® 恒定电流:是 恒定电压:- 拓扑:PWM，降压（降压） 输出数:1 内部驱动器:无 类型 - 主要:- 类型 - 次要:高亮度 LED（HBLED） 频率:30kHz ~ 1MHz 电源电压:8 V ~ 12 V 输出电压:- 安装类型:表面贴装 封装/外壳:14-SOIC（0.154"，3.90mm 宽） 供应商设备封装:14-SOICN 包装:管件 工作温度:-40°C ~ 125°C 产品目录页面:1285 (CN2011-ZH PDF) 其它名称:LM3445M |
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| A8512ELBTR-T | 功能描述:IC LED DVR WHT/RGB BKLGT 24SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 恒定电流:- 恒定电压:- 拓扑:升压（升压），切换式电容器（充电泵） 输出数:1 内部驱动器:是 类型 - 主要:背光 类型 - 次要:白色 LED 频率:625kHz ~ 875kHz 电源电压:2.7 V ~ 5.3 V 输出电压:5V 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽） 供应商设备封装:10-µMAX 包装:带卷 (TR) 工作温度:-40°C ~ 85°C |
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