参数资料
| 型号： | MIC2174-1YMM TR |
| 厂商： | Micrel Inc |
| 文件页数： | 14/27页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 10-MSOP |
| 产品培训模块： | MIC2124 Synchronous Current Mode DC-DC Buck Controller |
| 标准包装： | 2,500 |
| 系列： | Hyper Speed Control™ |
| PWM 型： | 混合物 |
| 输出数： | 1 |
| 频率 - 最大： | 375kHz |
| 占空比： | 87% |
| 电源电压： | 3 V ~ 40 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： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
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Micrel, Inc.
Application Information
MOSFET Selection
The MIC2174/MIC2174C controller works from input
voltages of 3V to 40V and has an external 3V to 5.5V V IN
to provide power to turn the external N-Channel power
MOSFETs for the high- and low-side switches. For
applications where V IN < 5V, it is necessary that the
power MOSFETs used are sub-logic level and are in full
MIC2174/MIC2174C
The low-side MOSFET is turned on and off at V DS = 0
because an internal body diode or external freewheeling
diode is conducting during this time. The switching loss
for the low-side MOSFET is usually negligible. Also, the
gate-drive current for the low-side MOSFET is more
accurately calculated using C ISS at V DS = 0 instead of
gate charge.
For the low-side MOSFET:
conduction mode for V GS of 2.5V. For applications when
V IN > 5V; logic-level MOSFETs, whose operation is
specified at V GS = 4.5V must be used.
I G[low - side] (avg) = C ISS × V GS × f SW
(6)
There are differing criteria for choosing the high-side and
low-side MOSFETs. These differences are more
significant at lower duty cycles, such as a 12V to 1.8V
conversion. In such an application, the high-side
MOSFET is required to switch as quickly as possible to
minimize transition losses, whereas the low-side
MOSFET can switch slower, but must handle larger
RMS currents. When the duty cycle approaches 50%,
the current carrying capability of the high-side MOSFET
starts to become critical.
It is important to note that the on-resistance of a
MOSFET increases with increasing temperature. A 75°C
rise in junction temperature will increase the channel
resistance of the MOSFET by 50% to 75% of the
resistance specified at 25°C. This change in resistance
must be accounted for when calculating MOSFET power
dissipation and in calculating the value of current limit.
Total gate charge is the charge required to turn the
MOSFET on and off under specified operating conditions
Since the current from the gate drive comes from the V IN ,
the power dissipated in the MIC2174/MIC2174C due to
gate drive is:
P GATEDRIVE = V IN × (I G[high - side] (avg) + I G[low - side] (avg)) (7)
A convenient figure of merit for switching MOSFETs is
the on resistance times the total gate charge R DS(ON) ×
Q G . Lower numbers translate into higher efficiency. Low
gate-charge logic-level MOSFETs are a good choice for
use with the MIC2174/MIC2174C. Also, the R DS(ON) of
the low-side MOSFET will determine the current limit
value. Please refer to “Current Limit” subsection in
“Functional Description” for more details.
Parameters that are important to MOSFET switch
selection are:
? Voltage rating
(V DS and V GS ). The gate charge is supplied by the
MIC2174/MIC2174C gate-drive circuit. At 300kHz
switching frequency and above, the gate charge can be
?
?
On-resistance
Total gate charge
a significant source of power dissipation in the
MIC2174/MIC2174C. At low output load, this power
dissipation is noticeable as a reduction in efficiency. The
average current required to drive the high-side MOSFET
is:
The voltage ratings for the high-side and low-side
MOSFETs are essentially equal to the power stage input
voltage V HSD . A safety factor of 20% should be added to
the V DS (max) of the MOSFETs to account for voltage
spikes due to circuit parasitic elements.
where:
I G[high - side] (avg) = Q G × f SW
(5)
The power dissipated in the MOSFETs is the sum of the
conduction losses during the on-time (P CONDUCTION ) and
the switching losses during the period of time when the
MOSFETs turn on and off (P AC ):
P CONDUCTION = I SW(RMS) × R DS(ON)
I G[high-side] (avg) = Average high-side MOSFET gate
current
Q G = Total gate charge for the high-side MOSFET taken
from the manufacturer’s data sheet for V GS = V IN .
f SW = Switching Frequency (300kHz)
P SW = P CONDUCTION + P AC
2
P AC = P AC(off ) + P AC(on)
where:
R DS(ON) = on-resistance of the MOSFET switch
D = Duty Cycle = V OUT / V HSD
(8)
(9)
(10)
September 2010
14
M9999-091310-C
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2174C | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:Synchronous Buck Controller Featuring Adaptive On-Time Control 40V Input, 300kHz |
| MIC2174C-1YMM | 功能描述:DC/DC 开关控制器 Low Cost 40V Synchronous 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 |
| MIC2174C-1YMM TR | 功能描述:DC/DC 开关控制器 Low Cost 40V Synchronous 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 |
| MIC2176-1 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:Wide Input Voltage, Synchronous Buck Controllers Featuring Adaptive On-Time Control |
| MIC2176-1YMM | 功能描述:DC/DC 开关控制器 76V Synchronous 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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