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| 型号： | MIC2182-5.0BSM |
| 厂商： | Micrel Inc |
| 文件页数： | 19/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-SSOP |
| 标准包装： | 77 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 330kHz |
| 占空比： | 86% |
| 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 ~ 85°C |
| 封装/外壳： | 16-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
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MIC2182
The input voltage ripple will primarily depend on the input
capacitors ESR. The peak input current is equal to the peak
inductor current, so:
? V IN = I inductor(peak) × R ESR(C IN )
The input capacitor must be rated for the input current ripple.
The RMS value of input capacitor current is determined at the
maximum output current. Assuming the peak to peak induc-
tor ripple current is low:
Micrel
? Supply current to the MIC2182
? MOSFET gate-charge power (included in the IC
supply current)
? Core losses in the output inductor
To maximize efficiency at light loads:
? Use a low gate-charge MOSFET or use the
smallest MOSFET, which is still adequate for
maximum output current.
I C IN (rms) ≈ I OUT(max) ×
D × (1 ? D)
? Allow the MIC2182 to run in skip mode at lower
currents.
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 MIC2182-3.3 and MIC2182-5.0 ICs contain internal
voltage dividers that set the output voltage. The MIC2182
adjustable version requires two resistors to set the output
voltage as shown in Figure 13.
? Use a ferrite material for the inductor core, which
has less core loss than an MPP or iron power
core.
Under heavy output loads the significant 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
Error
Amp
FB
7
R1
R2
? Input capacitor resistive losses (due to the
capacitors ESR)
To minimize power loss under heavy loads:
? Use logic-level, low on-resistance MOSFETs.
MIC2182 [adj.]
V REF
1.245V
Multiplying the gate charge by the on-resistance
gives a Figure of merit, providing a good bal-
ance between low and high load efficiency.
Figure 13. Voltage-Divider Configuration
The output voltage is determined by the equation:
? Slow transition times and oscillations on the
voltage and current waveforms dissipate more
power during turn-on and turnoff of the
V O = V REF × ? 1 +
?
?
?
R1 ?
R2 ?
MOSFETs. A clean layout will minimize parasitic
inductance and capacitance in the gate drive
Where: V REF for the MIC2182 is typically 1.245V.
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
efficiency of the power supply, especially at low output loads.
Once R1 is selected, R2 can be calculated using:
and high current paths. This will allow the fastest
transition times and waveforms without oscilla-
tions. 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
R2 =
V REF × R1
V O ? V REF
resistance. However, using too small of a value
will require more output capacitors to filter the
output ripple, which will force a smaller band-
I divider = 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:
P divider = (R1 + R2) × I divider 2
Efficiency Calculation and Considerations
Efficiency is the ratio of output power to input power. The
difference is dissipated as heat in the buck converter. Under
light output load, the significant contributors are:
width, 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 4.7 μ F decoupling capacitor is used to minimize noise on
the VDD pin. The placement of this capacitor is critical to the
proper operation of the IC. It must be placed right next to the
April 22, 2004
19
M9999-042204
相关PDF资料 |
PDF描述 |
|---|---|
| MIC2182-5.0BM TR | IC REG CTRLR BUCK PWM CM 16-SOIC |
| MIC2182-5.0BM | IC REG CTRLR BUCK PWM CM 16-SOIC |
| MIC2182-3.3BSM TR | IC REG CTRLR BUCK PWM CM 16-SSOP |
| MIC2182-3.3BSM | IC REG CTRLR BUCK PWM CM 16-SSOP |
| MIC2182-3.3BM TR | IC REG CTRLR BUCK PWM CM 16-SOIC |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2182BM | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 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 ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
| MIC2182BM TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 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 ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
| MIC2182BSM | 功能描述:DC/DC 开关控制器 High EfficiencySynchronous Buck Controller SSOP Pkg 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 |
| MIC2182BSM TR | 功能描述:DC/DC 开关控制器 High EfficiencySynchronous Buck Controller SSOP Pkg 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 |
| MIC2182BSMTR | 制造商:Rochester Electronics LLC 功能描述: 制造商:RF Micro Devices Inc 功能描述: |
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