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參數(shù)資料
| 型號(hào)： | MIC2199 |
| 廠商： | Micrel Semiconductor,Inc. |
| 英文描述： | 300kHz 4mm 】 4mm Synchronous Buck Converter |
| 中文描述： | 300kHz的4毫米】4mm的同步降壓轉(zhuǎn)換器 |
| 文件頁(yè)數(shù)： | 13/15頁(yè) |
| 文件大小： | 222K |
| 代理商： | MIC2199 |
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November 2004
13
MIC2199
MIC2199
Micrel
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:
I
I
D (1 D)
C (rms)
OUT(max)
≈
×
The power dissipated in the input capacitor is:
P
I
R
DISS(C )
C (rms)
ESR(C )
2
=
×
Voltage Setting Components
The MIC2199 requires two resistors to set the output voltage
as shown in Figure 6.
Error
Amp
3
MIC2199
FB
V
0.8V
R2
R1
Figure 6. Voltage-Divider Configuration
The output voltage is determined by the equation:
V
V
1
R1
R2
O
REF
=
×
+
Where: V
REF
for the MIC2199 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
efficiency of the power supply, especially at low output loads.
Once R1 is selected, R2 can be calculated using:
R2
V
V
R1
V
REF
O
REF
=
×
Voltage Divider Power Dissipation
The reference voltage and R2 set the current through the
voltage divider.
I
V
R2
DIVIDER
REF
=
The power dissipated by the divider resistors is:
P
(R1 R2) I
DIVIDER
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:
Supply current to the MIC2199
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 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.
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
Input capacitor resistive losses (due to the capaci-
tors ESR)
To minimize power loss under heavy loads:
Use logic-level, low on-resistance MOSFETs. Mul-
tiplying the gate charge by the on-resistance gives
a figure of merit, providing a good balance be-
tween low and high load efficiency.
Slow transition times and oscillations on the volt-
age 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 resis-
tance. However, using too small of a value will
require more output capacitors to filter 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 de-
crease the power dissipated in the resistor. How-
ever, it will also increase the overcurrent limit and
will require larger MOSFETs and inductor compo-
nents.
Use low-ESR input capacitors to minimize the
power dissipated in the capacitors ESR.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MIC2199_10 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:300kHz 4mm × 4mm Synchronous Buck Converter |
| MIC2199BML | 功能描述:IC REG CTRLR BUCK PWM CM 12-MLF RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| MIC2199BML TR | 功能描述:IC REG CTRLR BUCK PWM CM 12-MLF RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| MIC2199YML | 功能描述:DC/DC 開關(guān)控制器 300KHz 12 Lead Sync Buck Controller - Lead Free RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MIC2199YML EV | 功能描述:電源管理IC開發(fā)工具 300KHz 12 Lead Sync Buck Controller - Evaluation Board RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
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