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| 型号： | MIC2155YML TR |
| 厂商： | Micrel Inc |
| 文件页数： | 26/35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.
For the low-side switch, the DC power dissipation is:
I
P SWITCH 2 ( DC ) = R DSON 2 × ( SW 2 ( rms ) ) 2
The switching loss for each of the high-side MOSFETs
is:
P AC = V IN × I SW ( peak ) × T t × f S
The total power dissipation for each MOSFET is:
P FET _ total = P SWITCH 1 ( DC ) + P AC
External Schottky Diode
A freewheeling diode in parallel with the low-side FET is
needed to keep the inductor current flow continuous
while both MOSFETs are turned off (dead time). Dead
time is necessary to prevent current from flowing
unimpeded through both MOSFETs. An external
Schottky diode is not necessary for circuit operation
since the low-side MOSFET contains a parasitic body
diode. An external diode will improve efficiency due to its
lower forward voltage drop as compared to the internal
parasitic diode in the FET. It may also decrease high
frequency noise because the schottky diode junction
does not suffer from reverse recovery.
If the MOSFET body diode is used, it must be rated to
handle the peak and average current. The body diode
may have a relatively slow reverse recovery time and a
relatively high forward voltage drop. The power lost in
the diode is proportional to the forward voltage drop of
the diode. As the high-side MOSFET starts to turn on,
the body diode becomes a short circuit for the reverse
recovery period, dissipating additional power. The diode
recovery and the circuit inductance will cause ringing
during the high-side MOSFET turn on. If the internal FET
diode is used, power dissipated during the dead time
MIC2155/2156
This power dissipation is calculated below:
I D ( ave ) = I OUT × 2 × t d × f S
Where:
t d is the dead time when both MOSFETs are off.
The reverse voltage requirement of the diode is:
V DIODE _ RRM = V IN
The power dissipated by the diode is:
P DIODE = I D _ AVE × V F
Where:
V F is the forward voltage at the peak diode current.
Snubber Design
A snubber is used to damp out high frequency ringing
caused by parasitic inductance and capacitance in the
buck converter circuit. A snubber is needed for each of
the two phases in the converter. Figure 22 shows a
simplified schematic of one of the buck converter
phases. Stray capacitance consists mostly of the two
MOSFET’s output capacitance (C OSS ). The stray
inductance is mostly package and etch inductance. The
arrows show the resonant current path when the high
side MOSFET turns on. This ringing causes stress on
the semiconductors in the circuit as well as increased
EMI.
C OSS1
should be added to the P DISS of the low-side MOSFET.
An external Schottky diode conducts at a lower forward
voltage preventing the body diode in the MOSFET from
turning on. The lower forward voltage drop dissipates
+
L STRAY1
C IN
Q1
L STRAY2
L
L STRAY3
less power than the body diode. The lack of a reverse
recovery mechanism in a Schottky diode causes is less
ringing and power loss. Depending on the circuit
components and operating conditions, an external
V DC
Sync_buck
Controller
Q2
C OSS2
C OUT
Schottky diode may give a ?% to 1% improvement in
efficiency.
–
L STRAY4
Figure 22. Output Parasitics
November 2009
26
M9999-111209-B
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2156 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:Two-Phase, Single-Output, PWM Synchronous Buck Control IC |
| 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 |
| MIC2156YML-TR | 功能描述:Buck Regulator Positive Output Step-Down DC-DC Controller IC 32-MLF? (5x5) 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:过期 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:2 输出阶段:2 电压 - 电源（Vcc/Vdd）:4.5 V ~ 14.5 V 频率 - 开关:300kHz 占空比（最大）:0.8 同步整流器:是 时钟同步:是 串行接口:- 控制特性:限流，使能，电源良好，软启动 工作温度:-40°C ~ 125°C （TJ） 封装/外壳:32-VFQFN 裸露焊盘，32-MLF? 供应商器件封装:32-MLF?（5x5） 标准包装:1 |
| MIC2159 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:SYNCHRONOUS-itty⑩ Step-Down Converter IC |
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