收藏本站
Micrel, Inc.
Switching Frequency Set R FSW
To fi nd t he value of R FSW use the following equatio n:
R FSW (k ? ) ≈ 500 ? 0.3 × f SW (kHz )
R FSW (k ? ) ≈ 5 00 ? 0.3 × (1000) = 200k ?
Use 200kHz for R FSW (R5).
MIC3263
Inductor Selection
First calculate the RMS input current (n ominal, minimum,
and maximum) for the syste m given the operating
conditions listed in the desig n example table. The
minimum val ue of the RMS input current is necessary to
ensure proper operation. Using Equation 7, the following
values have been calculated:
Equation 7 :
Dim mi n g Frequency Sele c t Resis tor R DFS
F DIM is 5kHz therefore HF m ode is used. Connect MODE
to V DD . To find R DFS (R8) use the following equation:
R DFS (in k ? ) = 432 ? 20 × F DIM (in kHz)
= 432 ? 20 × 10 = 232(k ? )
The input frequency to the DRC pin can b e 10 0Hz to
I IN_RMS(MAX) =
I IN_RMS(NOM) =
I IN_RMS(MIN) =
V OUT(MIN) ×I OUT(MIN)
= 0.43A (RMS)
eff × V IN(MAX)
V OUT(NOM) ×I OUT(NOM)
= 0.53A (RMS)
eff × V IN(NOM)
V OUT(MAX) ×I OUT(MAX)
= 0.9A (RMS)
eff × V IN(MIN)
40kHz and the internal dimming frequ ency DR will
always be 5kHz.
The duty cycle of the input frequency a t D RC is
converte d according to Table 2 for the actual d imming
duty cycle.
Since the dim ming frequency is high the filter R6 and C6
is not necessary. They may be used with no ill effe ct.
Operating Duty Cycle
The operating duty cycle can be calculated using
Equation 6.
Equation 6:
I OUT is the same as I LED tot al
Selecting the inductor current (p eak-to-peak) I L_PP to be
between 20% to 50% of I IN_RMS(m ax) , in this case 40%, we
obtain:
I L_PP(MAX) = 0.40 × I IN_RMS(MAX) = 0 .4 × 0.9 = 0.36A PP
There is a trade off between the inductor value and the
minimum PWM dimming pulse. The larger the inductor,
the longer the PWM dimming pulse time will be. Due to
this, the percentage of the ripple current may be limited
by the required PWM dimming pulse. Also, the internal
D NOM =
D MAX =
( V OUT(NOM) - eff × V IN(NOM) )
( V OUT(MAX) - eff × V IN(MAX) )
V OUT(NOM)
V OUT(MAX)
current amplifiers will attenuate the LED ripple current by
more than a magnitude. It is recommended to operate in
the continuous conduction mode. The value of “L” in
Equation 8 represents Continuous Conduction Mode.
Equation 8:
D MIN =
( V OUT(MAX) - eff × V IN(MAX)
V OUT(MAX)
)
L=
V IN × D
I L_PP × F SW
Therefore D NOM = 66%, D MAX = 80% and D MIN = 58%.
January 2010
24
M9999-012110
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
MIC3287-24YD6 TR IC LED DRIVR WHITE BCKLGT TSOT-6
MIC3289-16YD6 TR IC LED DRIVR WHITE BCKLGT TSOT-6
MIC3291-18YML TR IC PWM WLED DVR 1.8V 1.2MHZ 8MLF
MIC4100YM IC DRIVER MOSFET 100V CMOS 8SOIC
MIC4102YM IC DRIVER MOSFET 100V TTL 8SOIC
MIC4103YM IC MOSFET DRIVER 100V CMOS 8SOIC
MIC4124YME IC MOSFET DRVR DUAL NONINV 8SOIC
MIC4128YMME IC DRIVER MOSFET 1.5A DUAL 8MSOP
相关代理商/技术参数
MIC3263YML-TR 功能描述:LED 驱动器 IC 6 输出 DC DC 稳压器 升压（升压） PWM 调光 30mA 24-MLF?（4x4） 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:停产 类型:DC DC 稳压器 拓扑:升压（升压） 内部开关:是 输出数:6 电压 - 供电（最低）:6V 电压 -?供电（最高）:40V 电压 - 输出:- 电流 - 输出/通道:30mA 频率:1.2MHz 调光:PWM 应用:背光 工作温度:-40°C ~ 125°C （TJ） 安装类型:表面贴装 封装/外壳:24-VFQFN 裸露焊盘，24-MLF? 供应商器件封装:24-MLF?（4x4） 标准包装:1
MIC3287 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:1.2MHz PWM White LED Driver with OVP in Thin SOT-23 and 2mm x 2mm MFL
MIC3287_10 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:1.2MHz PWM White LED Driver with OVP in Thin SOT-23 and 2mm x 2mm MFL
MIC3287-24YD6 制造商:Rochester Electronics LLC 功能描述: 制造商:RF Micro Devices Inc 功能描述:
MIC3287-24YD6 TR 功能描述:LED照明驱动器 2x2mm White LED Driver w/ 24V OVP (Lead Free) RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N
MIC3287-24YD6TR 制造商:RF Micro Devices Inc 功能描述:
MIC3287-24YD6-TR 功能描述:LED 驱动器 IC 1 输出 DC DC 稳压器 升压（升压） 模拟，PWM 调光 350mA（开关） TSOT-23-6 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:停产 类型:DC DC 稳压器 拓扑:升压（升压） 内部开关:是 输出数:1 电压 - 供电（最低）:2.8V 电压 -?供电（最高）:6.5V 电压 - 输出:36V 电流 - 输出/通道:350mA（开关） 频率:1.2MHz 调光:模拟，PWM 应用:背光 工作温度:-40°C ~ 125°C （TJ） 安装类型:表面贴装 封装/外壳:SOT-23-6 细型，TSOT-23-6 供应商器件封装:TSOT-23-6 标准包装:1
MIC3287-24YML 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:1.2MHz PWM White LED Driver with OVP in Thin SOT-23 and 2mm x 2mm MFL