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参数资料
| 型号： | MIC2198YML |
| 厂商： | Micrel Inc |
| 文件页数： | 12/14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 |
MIC2198
The power dissipated in the input capacitor is:
P DISS(C IN ) = I C IN (rms) 2 × R ESR(C IN )
Voltage Setting Components
The MIC2198 requires two resistors to set the output voltage
as shown in Figure 6.
Micrel, Inc.
Under heavy output loads the signi?cant contributors to power
loss are (in approximate order of magnitude):
? Resistive on-time losses in the MOSFETs
? Switching transition losses in the MOSFETs
? Inductor resistive losses
? Current-sense resistor losses
MIC2198
Error
Amp
V REF
0.8V
FB
3
R1
R2
? Input capacitor resistive losses (due to the capaci-
tors ESR)
To minimize power loss under heavy loads:
? Use logic-level, low on-resistance MOSFETs.
Multiplying the gate charge by the on-resistance
gives a ?gure of merit, providing a good balance
between low and high load ef?ciency.
V O = V REF × ? 1 + ?
V REF × R1
I DIVIDER = REF
P DIVIDER = (R1 + R2) × I DIVIDER
Figure6. Voltage-DividerCon?guration
The output voltage is determined by the equation:
? R1 ?
? R2 ?
Where: V REF for the MIC2198 is typically 0.8V.
A typical value of R1 can be between 3k and 10k. If R1 is
too large it may allow noise to be introduced into the voltage
feedback loop. If R1 is too small in value it will decrease
the ef?ciency of the power supply, especially at low output
loads.
Once R1 is selected, R2 can be calculated using:
R2 =
V O ? V REF
Voltage Divider Power Dissipation
The reference voltage and R2 set the current through the
voltage divider.
V
R2
The power dissipated by the divider resistors is:
2
Ef?ciency Calculation and Considerations
Ef?ciency is the ratio of output power to input power. The
difference is dissipated as heat in the buck converter. Under
light output load, the signi?cant contributors are:
? Supply current to the MIC2198
? MOSFET gate-charge power (included in the IC
supply current)
? Core losses in the output inductor
To maximize ef?ciency at light loads:
? Use a low gate-charge MOSFET or use the small-
est MOSFET, which is still adequate for maximum
output current.
? Use a ferrite material for the inductor core, which
has less core loss than an MPP or iron power
core.
? Slow transition times and oscillations on the voltage
and current waveforms dissipate more power during
turn-on and turnoff of the MOSFETs. A clean layout
will minimize parasitic inductance and capacitance
in the gate drive and high current paths. This will
allow the fastest transition times and waveforms
without oscillations. Low gate-charge MOSFETs
will transition faster than those with higher gate-
charge requirements.
? For the same size inductor, a lower value will
have fewer turns and therefore, lower winding re-
sistance. However, using too small of a value will
require more output capacitors to ?lter the output
ripple, which will force a smaller bandwidth, slower
transient response and possible instability under
certain conditions.
? Lowering the current-sense resistor value will
decrease the power dissipated in the resistor.
However, it will also increase the overcurrent
limit and will require larger MOSFETs and inductor
components.
? Use low-ESR input capacitors to minimize the
power dissipated in the capacitors ESR.
Decoupling Capacitor Selection
The 4.7μF decoupling capacitor is used to minimize noise on
the V DD pin. The placement of this capacitor is critical to the
proper operation of the IC. It must be placed right next to the
pins and routed with a wide trace. The capacitor should be a
good quality tantalum. An additional 1μF ceramic capacitor
may be necessary when driving large MOSFETs with high
gate capacitance. Incorrect placement of the V DD decoupling
capacitor will cause jitter or oscillations in the switching wave-
form and large variations in the overcurrent limit.
A 0.1μF ceramic capacitor is required to decouple the V IN .
The capacitor should be placed near the IC and connected
directly to between pin 6 (V IN ) and pin 9 (GND).
MIC2198
12
October 2005
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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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