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参数资料
| 型号： | MIC2155YML TR |
| 厂商： | Micrel Inc |
| 文件页数： | 18/35页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 32MLF |
| 特色产品： | MIC2155/6 Buck Control IC |
| 标准包装： | 1 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 550kHz |
| 占空比： | 80% |
| 电源电压： | 4.5 V ~ 14.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 32-VFQFN 裸露焊盘，32-MLF? |
| 包装： | 标准包装 |
| 产品目录页面： | 1091 (CN2011-ZH PDF) |
| 其它名称： | 576-3527-6 |
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Micrel, Inc.
The MIC2155/6 current limit circuit restricts the
maximum output current. If the load tries to draw
additional current the output voltage drops until it is no
longer within regulation limits. At this point (75% of
nominal output voltage) a hiccup current mode is
initiated to protect down stream loads from excessive
current during hard short circuits. This helps reduce the
overall power dissipation in the PWM converter
MIC2155/2156
Accurate Method
For designs where ripple current is significant when
compared to I OUT or for low duty cycle operation,
calculating the current setting resistor R CS should take
into account that we are sensing the peak inductor
current and that there is a blanking delay of
approximately 100ns.
I PK = + RIPPLE
components during a fault.
Figure 15. Overcurrent waveform
The equations to accurately calculate the current limit
resistor value are shown below:
I OUT I
2 2
V OUT × ( 1 ? D )
I RIPPLE =
I SET PK ? OUT
V × T DLY
I SET × R DSON ( MAX )
R CS =
Figure 14. Overcurrent Sense Waveforms
The MIC2155/6 only senses current across the low side
MOSFET of Channel 1 since both channels operate in
parallel. This means the total output current limit is
approximately twice the calculated current limit.
Current Limit Setting
The current limit circuit responds to the peak inductor
current flowing through the low-side FET. The value of
R CS can be estimated with the “simple” method or can be
more accurately calculated by taking the inductor ripple
current into account.
The Simple Method
Current limit can be quickly estimated with the following
equation:
R CS = I OUT /2 × R DSON(MAX) /180μA.
Where: R DSON is the maximum on-resistance of the low
side FET at the operating junction temperature
F S × L
= I
L
I CS ( MIN )
D = Duty Cycle
F S = Switching Frequency
L = Power inductor value
T DLY = Current limit blanking time ~ 100ns
I CS(min) = 180μA
Example:
Consider a 12V to 3.3V @ 30A converter with 1.5μH
power inductor and 90% efficiency at full load. Each
channel will supply 15A at a 500kHz (MIC2155)
switching frequency. The on-resistance of the low side
MOSFET is 6m ? .
Using the simple method:
× 6 m Ω
November 2009
18
R CS
=
30 A
2
180 μ A
= 500 Ω
M9999-111209-B
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相关代理商/技术参数 |
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| MIC2156YML | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2-Phase, Single Output, PWM Synchronous Buck Control IC |
| MIC2156YML TR | 功能描述:DC/DC 开关控制器 Single Output, PWM Sync Buck Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
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