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| 型号： | MIC2940A-3.3BU |
| 厂商： | Micrel Inc |
| 文件页数： | 7/11页 |
| 文件大小： | 0K |
| 描述： | IC REG LDO 3.3V 1.25A TO263 |
| 标准包装： | 50 |
| 稳压器拓扑结构： | 正，固定式 |
| 输出电压： | 3.3V |
| 输入电压： | 最高 26V |
| 电压 - 压降（标准）： | 0.4V @ 1.25A |
| 稳压器数量： | 1 |
| 电流 - 输出： | 1.25A |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | TO-263-4，D²Pak（3 引线+接片），TO-263AA |
| 供应商设备封装： | TO-263-3 |
| 包装： | 管件 |
C BYPASS ?
Micrel, Inc.
Application Information
External Capacitors
A 10μF (or greater) capacitor is required between the
MIC2940A output and ground to prevent oscillations due
to instability. Most types of tantalum or aluminum
electrolytics will be adequate; ? lm types will work, but
are costly and therefore not recommended. Many
aluminum electrolytics have electrolytes that freeze at
about –30°C, so solid tantalums are recommended for
operation below –25°C. The important parameters of the
capacitor are an effective series resistance of about 5 ?
or less and a resonant frequency above 500kHz. The
value of this capacitor may be increased without limit.
At lower values of output current, less output
capacitance is required for output stability. The capacitor
can be reduced to 3.3μF for current below 100mA or
2.2μF for currents below 10mA. Adjusting the MIC2941A
to voltages below 5V runs the error ampli ? er at lower
gains so that more output capacitance is needed. For
the worst-case situation of a 1.25A load at 1.23V output
(Output shorted to Adjust) a 22μF (or greater) capacitor
should be used.
The MIC2940A will remain stable and in regulation with
load currents ranging from 5mA on up to the full 1.25A
rating. The external resistors of the MIC2941A version
may be scaled to draw this minimum load current.
A 0.22μF capacitor should be placed from the
MIC2940A input to ground if there is more than 10
inches of wire between the input and the AC ? lter
capacitor or if a battery is used as the input.
Programming the Output Voltage (MIC2941A)
The MIC2941A may be programmed for any output
voltage between its 1.235V reference and its 26V
maximum rating. An external pair of resistors is required,
as shown in Figure 3.
V OUT = V REF x { 1 + R 1 /R 2 } – |I FB | R 1
MIC2940A/2941A
Reducing Output Noise
In reference applications it may be advantageous to
reduce the AC noise present at the output. One method
is to reduce the regulator bandwidth by increasing the
size of the output capacitor. This is relatively inef ? cient,
as increasing the capacitor from 1μF to 220μF only
decreases the noise from 430μV to 160μV RMS for a
100kHz bandwidth at 5V output. Noise can be reduced
by a factor of four with the MIC2941A by adding a
bypass capacitor across R 1 . Pick
1
2 π R 1 200Hz
or about 0.01μF. When doing this, the output capacitor
must be increased to 22μF to maintain stability. These
changes reduce the output noise from 430μV to
100μV RMS for a 100kHz bandwidth at 5V output. With the
bypass capacitor added, noise no longer scales with
output voltage so that improvements are more dramatic
at higher output voltages.
Automotive Applications
The MIC2940A is ideally suited for automotive
applications for a variety of reasons. It will operate over
a wide range of input voltages with very low dropout
voltages (40mV at light loads), and very low quiescent
currents (240μA typical). These features are necessary
for use in battery powered systems, such as
automobiles. It is a “bulletproof” device with the ability to
survive both reverse battery (negative transients up to
20V below ground), and load dump (positive transients
up to 60V) conditions. A wide operating temperature
range with low temperature coef ? cients is yet another
reason to use these versatile regulators in automotive
designs.
4.75V
OUTPUT
VOLTAGE
where V REF is the nominal 1.235 reference voltage and
I FB is the Adjust pin bias current, nominally 20nA. The
minimum recommended load current of 1μA forces an
upper limit of 1.2M ? on the value of R 2 , if the regulator
must work with no load (a condition often found in
CMOS in standby), I FB will produce a –2% typical error in
V OUT which may be eliminated at room temperature by
trimming R 1 . For better accuracy, choosing R 2 = 100k ?
reduces this error to 0.17% while increasing the resistor
program current to 12μA. Since the MIC2941A typically
ERROR
INPUT
VOLTAGE
NOT *
VALID
1.3V
5V
NOT *
VALID
draws 100μA at no load with SHUTDOWN open-
circuited, this is a negligible addition.
Figure 1. ERROR Output Timing
July 2007
7
M9999-071307
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2940A-5.0BT | 功能描述:IC REG LDO 5V 1.25A TO220-3 RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 系列:- 标准包装:3,000 系列:- 稳压器拓扑结构:正，固定式 输出电压:3.8V 输入电压:最高 16V 电压 - 压降（标准）:0.3V @ 80mA 稳压器数量:1 电流 - 输出:80mA 电流 - 限制（最小）:- 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:SC-74A，SOT-753 供应商设备封装:SOT-23-5 包装:带卷 (TR) 其它名称:MIC5203-3.8BM5TRMIC5203-3.8BM5TR-ND |
| MIC2940A-5.0BU | 功能描述:IC REG LDO 5V 1.25A TO263 RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 系列:- 标准包装:3,000 系列:- 稳压器拓扑结构:正，固定式 输出电压:3.8V 输入电压:最高 16V 电压 - 压降（标准）:0.3V @ 80mA 稳压器数量:1 电流 - 输出:80mA 电流 - 限制（最小）:- 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:SC-74A，SOT-753 供应商设备封装:SOT-23-5 包装:带卷 (TR) 其它名称:MIC5203-3.8BM5TRMIC5203-3.8BM5TR-ND |
| MIC2940A-5.0BU TR | 功能描述:IC REG LDO 5V 1.25A TO-263 RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 系列:- 标准包装:3,000 系列:- 稳压器拓扑结构:正，固定式 输出电压:3.8V 输入电压:最高 16V 电压 - 压降（标准）:0.3V @ 80mA 稳压器数量:1 电流 - 输出:80mA 电流 - 限制（最小）:- 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:SC-74A，SOT-753 供应商设备封装:SOT-23-5 包装:带卷 (TR) 其它名称:MIC5203-3.8BM5TRMIC5203-3.8BM5TR-ND |
| MIC2940A-5.0WT | 功能描述:低压差稳压器 - LDO 1.25A LDO Fixed Volt.(ROHS Compliant) RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MIC2940A-5.0WT | 制造商:Micrel Inc 功能描述:Linear Voltage Regulator IC |
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