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参数资料
| 型号： | MIC2198YML |
| 厂商： | Micrel Inc |
| 文件页数： | 9/14页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 12-MLF |
| 标准包装： | 300 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 550kHz |
| 占空比： | 76% |
| 电源电压： | 4.5 V ~ 32 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： | 12-VFDFN 裸露焊盘，12-MLF? |
| 包装： | 托盘 |
V OUT × (V IN(max) ? V OUT )
I PP =
R WINDING(hot) = R WINDING(20°C) × ? ? 1 + 0.0042 × (T HOT ? T 20°C ) ? ?
R SENSE =
I OVERCURRENT(max) =
1 ?
?
I INDUCTOR(rms) = I OUT(max) × 1 +
I P
3 ? I OUT(max) ?
MIC2198
Applications Information
The following applications information includes component
selection and design guidelines.
Inductor Selection
Values for inductance, peak, and RMS currents are required
to select the output inductor. The input and output voltages
and the inductance value determine the peak to peak induc-
tor ripple current. Generally, higher inductance values are
used with higher input voltages. Larger peak to peak ripple
currents will increase the power dissipation in the inductor
and MOSFETs. Larger output ripple currents will also require
more output capacitance to smooth out the larger ripple cur-
rent. Smaller peak to peak ripple currents require a larger
inductance value and therefore a larger and more expensive
inductor. A good compromise between size, loss and cost is
to set the inductor ripple current to be equal to 20% of the
maximum output current.
The inductance value is calculated by the equation below.
L =
V IN(max) × f S × 0.2 × I OUT(max)
where:
f S = switching frequency
0.2 = ratio of AC ripple current to DC output current
V IN(max) = maximum input voltage
The peak-to-peak inductor current (AC ripple current) is:
V OUT × (V IN(max) ?V OUT )
V IN(max) × f S × L
The peak inductor current is equal to the average output current
plus one half of the peak to peak inductor ripple current.
I PK = I OUT(max) + 0.5 × I PP
The RMS inductor current is used to calculate the I 2 × R losses
in the inductor.
2
? ?
Maximizing ef?ciency requires the proper selection of core
material and minimizing the winding resistance. The high
frequency operation of the MIC2198 requires the use of fer-
rite materials for all but the most cost sensitive applications.
Lower cost iron powder cores may be used but the increase
in core loss will reduce the ef?ciency of the power supply.
This is especially noticeable at low output power. The winding
resistance decreases ef?ciency at the higher output current
levels. The winding resistance must be minimized although
this usually comes at the expense of a larger inductor.
The power dissipated in the inductor is equal to the sum
of the core and copper losses. At higher output loads, the
core losses are usually insigni?cant and can be ignored. At
lower output currents, the core losses can be a signi?cant
contributor. Core loss information is usually available from
the magnetics vendor.
Micrel, Inc.
Copper loss in the inductor is calculated by the equation
below:
P INDUCTORCu = I INDUCTOR(rms) 2 × R WINDING
The resistance of the copper wire, R WINDING , increases with
temperature. The value of the winding resistance used should
be at the operating temperature.
? ?
where:
T HOT = temperature of the wire under operating load
T 20°C = ambient temperature
R WINDING(20°C) is room temperature winding
resistance (usually speci?ed by the manufacturer)
Current-Sense Resistor Selection
Low inductance power resistors, such as metal ?lm resistors
should be used. Most resistor manufacturers make low induc-
tance resistors with low temperature coef?cients, designed
speci?cally for current-sense applications. Both resistance
and power dissipation must be calculated before the resis-
tor is selected. The value of R SENSE is chosen based on the
maximum output current and the maximum threshold level.
The power dissipated is based on the maximum peak output
current at the minimum overcurrent threshold limit.
55mV
I OUT(max)
The maximum overcurrent threshold is:
95mV
R CS
The maximum power dissipated in the sense resistor is:
P D(R SENCE ) = I OVERCURRENT(max)2 × R CS
MOSFET Selection
External N-Channel logic-level power MOSFETs must be
used for the high- and low-side switches. The MOSFET
gate-to-source drive voltage of the MIC2198 is regulated by
an internal 5V V DD regulator. Logic-level MOSFETs, whose
operation is speci?ed at V GS = 4.5V must be used.
It is important to note the on-resistance of a MOSFET in-
creases with increasing temperature. A 75°C rise in junction
temperature will increase the channel resistance of the MOS-
FET by 50% to 75% of the resistance speci?ed at 25°C. This
change in resistance must be accounted for when calculating
MOSFET power dissipation.
Total gate charge is the charge required to turn the MOSFET
on and off under speci?ed operating conditions (V DS and
V GS ). The gate charge is supplied by the MIC2198 gate drive
circuit. At 500kHz switching frequency, the gate charge can
be a signi?cant source of power dissipation in the MIC2198.
At low output load this power dissipation is noticeable as a
reduction in ef?ciency. The average current required to drive
the high-side MOSFET is:
I G[high-side](avg) = Q G × f S
October 2005
9
MIC2198
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2198YML TR | 功能描述:DC/DC 开关控制器 500KHz 12 Lead Sync Buck Controller (Lead Free) 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 |
| MIC2198YMLTR | 制造商:Micrel 功能描述:DC-DC Controller Sync Buck 4.5V to 32V |
| MIC2198YML-TR | 功能描述:Buck Regulator Positive Output Step-Down DC-DC Controller IC 12-MLF? (4x4) 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:有效 输出类型:晶体管驱动器 功能:降压 输出配置:正 拓扑:降压 输出数:1 输出阶段:1 电压 - 电源（Vcc/Vdd）:4.5 V ~ 32 V 频率 - 开关:500kHz 占空比（最大）:0.76 同步整流器:是 时钟同步:无 串行接口:- 控制特性:使能 工作温度:-40°C ~ 125°C （TJ） 封装/外壳:12-VFDFN 裸焊盘，12-MLF? 供应商器件封装:12-MLF?（4x4） 标准包装:1 |
| MIC2199 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:300kHz 4mm 】 4mm Synchronous Buck Converter |
| MIC2199_10 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:300kHz 4mm × 4mm Synchronous Buck Converter |
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