收藏本站
Micrel, Inc.
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 MIC2289C 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 frequency
should be between 100Hz and 10kHz.
MIC2289C
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 MIC2289C to switch with a
high duty-cycle, resulting in output overvoltage. This
would normally cause the SW pin voltage to exceed its
maximum voltage rating, possibly damaging the IC and
the external components. However, the MIC2289C has a
dedicated OVP monitor to limit the output voltage within
safe levels (see Figure 3).
V IN
2. Continuous dimming control is implemented by
applying a DC control voltage to the FB pin of
the MIC2289C through a series resistor as
shown in Figure 2. The LED current is
decreased proportionally with the amplitude of
the control voltage. The LED intensity (current)
can be dynamically varied applying a DC voltage
to the FB pin. The DC voltage can come from a
DAC signal, or a ? ltered PWM signal. The
VIN
EN
SW
OUT
FB
GND
V IN
advantage of this approach is that a high
frequency PWM signal (>10kHz) can be used to
control LED intensity.
Figure 3. Thin SOT-23 Package OVP Circuit
Start-Up and Inrush Current
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
VIN
SW
OUT
Figure 4 could be implemented. The soft-start capacitor,
CSS, provides over-drive to the FB pin at start-up,
resulting in gradual increase of switch duty cycle and
limited inrush current.
PWM
EN
GND
FB
V IN
C SS
2200pF
V IN
Figure 1. PWM Dimming Method
VIN
SW
OUT
VIN
SW
EN
GND
FB
R
10k
OUT
Figure 4. One of Soft-Start Circuit
EN
GND
FB
5.11k
49.9k
DC
Equivalent
Figure 2. Continuous Dimming
August 2007
7
M9999-081507-B
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
MIC2291YD5 TR IC LED DRIVER PHOTO FLASH TSOT-5
MIC2293-15YML TR IC LED DRIVER WHITE BCKLGT 8-MLF
MIC2293C-34YML TR IC LED DRIVER WHITE BCKLGT 8-MLF
MIC2297-42YML TR IC LED DRIVR WHITE BCKLGT 10-MLF
MIC2298-15YML TR IC LED DRIVER HIGH BRIGHT 12-MLF
MIC2299-15YML TR IC LED DRIVR WHITE BCKLGT 12-MLF
MIC26603YJL EV BOARD EVAL FOR MIC26603YJL
MIC26901YJL EV BOARD EVAL FOR MIC26901YJL
相关代理商/技术参数
MIC2289C-34YML 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:White LED Driver Internal Schottky Diode and OVP
MIC2289CBD5 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:White LED Driver Internal Schottky Diode and OVP
MIC2289CYD5 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:White LED Driver Internal Schottky Diode and OVP
MIC2290 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2mm 】 2mm PWM Boost Regulator with Internal Schotty Diode
MIC2290_07 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2mm 】 2mm PWM Boost Regulator with Internal Schotty Diode
MIC2290BML 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2mm 】 2mm PWM Boost Regulator with Internal Schotty Diode
MIC2290BML TR 功能描述:IC REG BOOST ADJ 0.5A 8MLF 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
MIC2290YML 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2mm 】 2mm PWM Boost Regulator with Internal Schotty Diode