参数资料
| 型号： | MIC2150YML TR |
| 厂商： | Micrel Inc |
| 文件页数： | 12/27页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 24MLF |
| 标准包装： | 1 |
| PWM 型： | 电流/电压模式 |
| 输出数： | 2 |
| 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： | 24-VFQFN 裸露焊盘，24-MLF? |
| 包装： | 标准包装 |
| 其它名称： | 576-3746-6 |
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Micrel, Inc.
circuit acts to provide a fixed maximum output current
until the resistance of the load is so low that the voltage
across it is no longer within regulation limits. At this point
(75% of nominal output voltage), Hiccup current mode is
initiated to protect down-stream loads from excessive
current during hard short circuits and also reduces
overall power dissipation in the PWM converter
components during a fault. Before hiccup current mode
occurs, ‘brick wall’ current limiting is provided to prevent
system shutdown or disturbance if the overload is only
marginal.
Figure 4. Overcurrent Sensing
During the normal operation of a synchronous Buck
regulator, as the lower MOSFET is switched on, its drain
voltage will become negative with respect to ground as
the inductor current continues to flow from Source to
Drain. This negative voltage is proportional to output
load current, inductor ripple current and MOSFET R DSON .
MIC2150
pulse is missed and so on. Thus reducing the overall
energy transferred to the output and V OUT starts to fall.
As this successive missing of pulses results in an
effectively lower switching frequency, power inductor
ripple currents can get very high if left unlimited. The
MIC2150 therefore limits Duty Cycle during current limit
to prevent currents building up in the power inductor and
output capacitors.
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 ×R DSON(MAX) /200μA.
Where: R DSON is the maximum on-resistance of the low
side FET at the operating junction temperature
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 one is sensing the peak inductor
current and that there is a blanking delay of
approximately 100ns.
Figure 5. Current Sensing Waveforms
The larger inductor current, the more negative VDS
becomes. This is utilized for the detection of over current
Figure 6. Overcurrent-Circuit Waveform
Calculate peak switch current
I PK = I OUT +
by passing a known fixed current source (200μA)
through a resistor R CS which sets up an offset voltage
(I CS ×R CS ). When I SD (Source to Drain current)×R DSON is
equal to this voltage, the MIC2150’s over current trigger
is set. This disables the next high-side gate drive pulse.
I RIPPLE
2
Where: I RIPPLE =
V OUT × (1 ? D )
F S × L
After missing the high-side pulse, the over current (OC)
trigger is reset. If, on the next low-side drive cycle, the
current is still too high i.e., V CS is ≤ 0V, another high-side
Now calculate the actual set point to allow for the 100ns
delay.
August 2009
12
M9999-082809-A
(408) 944-0800
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2151 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2-Phase Dual Output PWM Synchronous Buck Control IC |
| MIC2151YML | 制造商:Micrel 功能描述:Micrel MIC2151YML |
| MIC2155 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:2-Phase, Single Output, PWM Synchronous Buck Control IC |
| MIC2155_0911 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:Two-Phase, Single-Output, PWM Synchronous Buck Control IC |
| MIC2155YML | 制造商:Micrel 功能描述:The Micrel MIC2155YML is a 50A Synchronous Buck Regulator. |
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