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参数资料
| 型号： | MIC3232YMM |
| 厂商： | Micrel Inc |
| 文件页数： | 10/19页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR HP CONS CURR 10-MSOP |
| 标准包装： | 100 |
| 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： | 通用 |
| 频率： | 400kHz |
| 电源电压： | 6 V ~ 45 V |
| 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-MSOP |
| 包装： | 管件 |
| 工作温度： | -40°C ~ 125°C |
| 产品目录页面： | 1082 (CN2011-ZH PDF) |
| 其它名称： | 576-3405-5 |
Micrel, Inc.
Dithering (MIC3231 Only)
The MIC3231 has a feature which dithers the switching
frequency by ±12%. The purpose of this dithering is to help
achieve a spread spectrum of the conducted EMI noise.
This can allow for an overall reduction in noise emission by
approximately 10dB.
Internal Gate Driver
External FETs are driven by the MIC323x’s internal low
impedance gate drivers. These drivers are biased from the
V DD and have a source resistance of 2 ? and a sink
resistance of 3.5 ? .
V DD
V DD is an internal linear regulator powered by V IN and V DD
is the bias supply for the internal circuitry of the MIC323x.
A 10μF ceramic bypass capacitor is required at the V DD pin
for proper operation. This pin is for filtering only and should
not be utilized for operation.
Current Limit
The MIC323x family features a current limit protection
feature to prevent any current runaway conditions. The
current limit circuitry monitors current on a pulse by pulse
basis. It limits the current through the inductor by sensing
the voltage across R CS . When 0.45V is present at the IS
pin, the pulse is truncated. The next pulse continues as
normally until the IS pin reaches 0.45V and it is truncated
once again. This will continue until the output load is
decreased.
Select R CS using Equation 5:
MIC3230/1/2
Current Sense I S
The IS pin monitors the rising slope of the inductor current
(m1 in Figure 5) and also sources a ramp current
(250μA/T) that flows through R SLC that is used for slope
compensation. This ramp of 250μA per period, T,
generates a ramped voltage across R SLC and is labeled V A
in Figure 3. The signal at the IS pin is the sum of V CS + V A
(as shown in Figure 3). The current sense circuitry and
block diagram is displayed in Figure 4. The IS pin is also
used as the current limit (see the previous section on
Current Limit).
Figure 3. Slope Compensation Waveforms
Soft Start
The boost switching convertor features a soft start in order
to power up in a controlled manner, thereby limiting the
inrush current from the line supply. Without this soft start,
the inrush current could be too high for the supply. To
prevent this, a soft start delay can be set using the
compensation capacitor (C COMP in Figure 1). For switching
to begin, the voltage on the compensation cap must reach
( V
)
Eq. (5)
R CS =
0 . 45
OUT MAX ? V IN MIN × D
L × F SW
+ I L PK _ LIMIT
about 0.7V. Switching starts with the minimum duty cycle
and increases to the final duty cycle. As the duty cycle
increases, V OUT will increase from V IN to its final value. A
6μA current source charges the compensation capacitor
and the soft start time can be calculated in Equation 7:
V OUT ? V IN MIN ) × R CS
Eq. (6) R SLC =
C COMP × V COMP_STEAD Y_STATE
Eq. (7) T SOFTSTART ≈
Where: V A PK =
× R SLC × D × T and
Slope Compensation
The MIC323x is a peak current mode controller and
requires slope compensation. Slope compensation is
required to maintain internal stability across all duty cycles
and prevent any unstable oscillations. The MIC323x uses
slope compensation that is set by an external resistor,
R SLC . The ability to set the proper slope compensation
through the use of a single external component results in
design flexibility. This slope compensation resistor, R SLC ,
can be calculated using Equation 6:
MAX
L × 250 μ A × F SW
where V IN_MAX and V OUT_MAX can be selected to system
specifications.
6 μ A
V COMP_STEADY_STATE is usually between 0.7V to 3V, but can
be as high as 5V.
Eq. (8) V COMP _ STEADY _ STATE = Ai × ( V A PK + Vcs PK )
I RAMP
T
V CS PK = I L _ PK × R CS
Ai = 1.4 V/V
D = Duty cycle (0 to1)
T = period
A 10nF ceramic capacitor will make this system stable at
all operating conditions.
March 2011
10
M9999-030311-D
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| MIC3232YMM EV | 功能描述:LED 照明开发工具 400kHz Fixed Frequency Boost Driver Controller for High Power LEDs - Evaluation Board RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装: |
| MIC3232YMM TR | 功能描述:LED照明驱动器 400kHz Fixed Frequency Boost Driver Controller for High Power LEDs 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 |
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| MIC3263YML EV | 制造商:Micrel Inc 功能描述: |
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