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| 型号： | MIC2287YD5 TR |
| 厂商： | Micrel Inc |
| 文件页数： | 7/10页 |
| 文件大小： | 0K |
| 描述： | IC LED DRIVR WHITE BCKLGT TSOT-5 |
| 标准包装： | 1 |
| 恒定电流： | 是 |
| 拓扑： | PWM，升压（升压） |
| 输出数： | 1 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光，闪灯/白光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 1.05MHz ~ 1.35MHz |
| 电源电压： | 2.5 V ~ 10 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | SOT-23-5 细型，TSOT-23-5 |
| 供应商设备封装： | TSOT-23-5 |
| 包装： | 标准包装 |
| 工作温度： | -40°C ~ 125°C |
| 产品目录页面： | 1082 (CN2011-ZH PDF) |
| 其它名称： | 576-1728-6 |
MIC2287
Dimming Control
There are two techniques for dimming control. One is PWM
dimming, and the other is continuous dimming.
1. PWM dimming control is implemented by applying
a PWM signal on EN pin as shown in Figure 1. The
MIC2287 is turned on and off by the PWM signal.
With this method, the LEDs operate with either zero
or full current. The average LED current is increased
proportionally to the duty-cycle of the PWM signal.
This technique has high-ef?ciency because the IC
and the LEDs consume no current during the off
cycle of the PWM signal. Typical PWM frequency
should be between 100Hz and 10kHz.
2. Continuous dimming control is implemented by
applying a DC control voltage to the FB pin of the
MIC2287 through a series resistor as shown in
Figure 2. The LED intensity (current) can be dy-
namically varied applying a DC voltage to the FB
pin. The DC voltage can come from a DAC signal,
or a ?ltered PWM signal. The advantage of this ap-
proach is a high frequency PWM signal (>10kHz)
that can be used to control LED intensity.
V IN
Micrel, Inc.
options for 15V, 24V, or 34V (see Figure 3). The reason for
the three OVP levels is to let users choose the suitable level
of OVP for their application. For example, a 3-LED application
would typically see an output voltage of no more than 12V, so
a 15V OVP option would offer a suitable level of protection.
This allows the user to select the output diode and capacitor
with the lowest voltage ratings, as well as smallest size and
lowest cost. The OVP will clamp the output voltage to within
the speci?ed limits. For the Thin SOT-23-5 package, an OVP
pin is not available. An external zener diode can be connected
from the output of the converter to FB pin as shown in Figure
4. to implement similar protection.
V IN
VIN SW
EN FB
GND OVP
Figure 3. MLF? Package OVP Circuit
V IN
VIN
SW
VIN
SW
PWM
EN
FB
EN
FB
5.11k
GND
GND
V IN
Figure 1. PWM Dimming Method
Figure 4. Thin SOT-23 Package OVP Circuit
Start-Up and Inrush Current
VIN
EN
SW
FB
GND
5.11k
49.9k
DC
Equivalent
During start-up, inrush current of approximately double the
nominal current ?ows to set up the inductor current and the
voltage on the output capacitor. If the inrush current needs
to be limited, a soft-start circuit similar to Figure 5 could be
implemented. The soft-start capacitor, C SS , provides over-
drive to the FB pin at start-up, resulting in gradual increase
of switch duty cycle and limited inrush current.
V IN
GND
Figure 2. Continuous Dimming
Open-Circuit Protection
If the LEDs are disconnected from the circuit, or in case
an LED fails open, the sense resistor will pull the FB pin to
ground. This will cause the MIC2287 to switch with a high
duty-cycle, resulting in output overvoltage. This may cause
the SW pin voltage to exceed its maximum voltage rating,
possibly damaging the IC and the external components. To
ensure the highest level of protection, the MIC2287 has 3
product options in the 8-lead 2mm × 2mm MLF? with over-
voltage protection (OVP). The extra pins of the 8-lead 2mm
× 2mm MLF? package allow a dedicated OVP monitor with
C SS
2200pF
VIN SW
EN FB
R
10k
Figure 5. Soft-Start Circuit
July 2005
7
M9999-070105
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2288 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:1A 1.2 MHZ PWM BOOST CONVERTER IN THIN SOT 23 AND 2 X MLF |
| MIC2288_05 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:1A 1.2MHz PWM Boost Converter in Thin SOT-23 and 2×2 MLF |
| MIC2288BD5 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:1A 1.2 MHZ PWM BOOST CONVERTER IN THIN SOT 23 AND 2 X MLF |
| MIC2288BD5 TR | 功能描述:IC REG BOOST ADJ 1A TSOT23-5 RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:20 系列:SIMPLE SWITCHER® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:12V 输入电压:4 V ~ 60 V PWM 型:电压模式 频率 - 开关:52kHz 电流 - 输出:1A 同步整流器:无 工作温度:-40°C ~ 125°C 安装类型:通孔 封装/外壳:16-DIP（0.300"，7.62mm） 包装:管件 供应商设备封装:16-DIP 其它名称:*LM2575HVN-12LM2575HVN-12 |
| MIC2288BML | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:1A 1.2MHz PWM Boost Converter in Thin SOT-23 and 2×2 MLF |
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