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参数资料
| 型号： | MIC2171WU TR |
| 厂商： | Micrel Inc |
| 文件页数： | 9/12页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG 2.5A TO263-5 |
| 标准包装： | 1 |
| 类型： | 降压（降压），升压（升压），反相，Cuk |
| 输出数： | 1 |
| 输入电压： | 3 V ~ 40 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 100kHz |
| 电流 - 输出： | 2.5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | TO-263-6，D²Pak（5 引线+接片），TO-263BA |
| 包装： | 标准包装 |
| 供应商设备封装： | TO-263-5 |
| 产品目录页面： | 1092 (CN2011-ZH PDF) |
| 其它名称： | 576-1541-6 |
Micrel, Inc.
For the practical example:
then:
MIC2171
V CE = 65V max. for the MIC2171
F CE = 0.8
a ≤
11.4
7.9
= 1 . 20
then:
V SEC = 5.6V
This ratio is less than the ratio calculated in equation (9).
When specifying the transformer it is necessary to know
a ≤
I PEAK(pri) =
V IN(min) T ON
0.5f SW V IN(min) T ON
I PEAK(pri) =
65 × 0.8 ? 6.0
5.6
a ≤ 8.2 (N PRI /N SEC )
Next, calculate the maximum primary inductance
required to store the needed output energy with a power
switch duty cycle of 55%.
2 2
(10) L PRI ≥
P OUT
where:
L PRI = maximum primary inductance
the primary peak current which must be withstood
without saturating the transformer core.
(13)
L PRI
so:
3.22 × 7.6 × 10 ? 6
L PRI
I PEAK(pri) = 2.1A
Now find the minimum reverse voltage requirement for
the output rectifier. This rectifier must have an average
V IN(max) + (V OUT a)
then:
f SW = device switching frequency (100kHz)
V IN(min) = minimum input voltage
T ON = power switch on time
current rating greater than the maximum output current
of 0.5A.
(14) V BR ≥
F BR a
L PRI ≥
0.5f SW V SEC T OFF
V BR ≥
L SEC ≤
0.5 × 1 × 10 5 × (3.22) 2 × (7.4 × 10 ? 6 )2
2.5
L PRI ≥ 11.4μH
Use a 12μH primary inductance to overcome circuit
inefficiencies.
To complete the design the inductance value of the
secondary is found which will guarantee that the energy
stored in the transformer during the power switch on
time will be completed discharged into the output during
the off-time. This is necessary when operating in
discontinuous-mode.
2 2
(11) L SEC ≤
P OUT
where:
L SEC = maximum secondary inductance
T OFF = power switch off time
then:
0.5 × 1 × 10 5 × (5.41) 2 × (2.6 × 10 ? 6 ) 2
2.5
L SEC ≤ 7.9μH
Finally, recalculate the transformer turns ratio to insure
that it is less than the value earlier found in equation (9).
where:
V BR = output rectifier maximum peak reverse
voltage rating
a = transformer turns ratio (1.2)
F BR = reverse voltage safety derating factor (0.8)
then:
6.0 + (5.0 × 1.2)
0.8 × 1.2
V BR ≥ 12.5V
A 1N5817 will safely handle voltage and current require-
ments in this example.
Forward Converters
Micrel’s MIC2171 can be used in several circuit
configurations to generate an output voltage which is
less than the input voltage (buck or step-down topology).
Figure 6 shows the MIC2171 in a voltage step-down
application. Because of the internal architecture of these
devices, more external components are required to
implement a step-down regulator than with other devices
offered by Micrel (refer to the LM257x or MIC457x family
of buck switchers). However, for step-down conversion
requiring a transformer (forward), the MIC2171 is a good
choice.
A 12V to 5V step-down converter using transformer
(12)
a ≤
L PRI
L SEC
isolation (forward) is shown in Figure 6. Unlike the
isolated flyback converter which stores energy in the
primary inductance during the controller’s on-time and
releases it to the load during the off-time, the forward
converter transfers energy to the output during the on-
May 2007
9
M9999-051107
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相关代理商/技术参数 |
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|---|---|
| MIC2172 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:100kHz 1.25A Switching Regulators |
| MIC2172_05 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:100kHz 1.25A Switching Regulators |
| MIC2172_06 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:100kHz 1.25A Switching Regulators |
| MIC2172BM | 功能描述:IC REG MULTI CONFIG 1.25A 8SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:20 系列:SIMPLE SWITCHER® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:12V 输入电压:4 V ~ 60 V PWM 型:电压模式 频率 - 开关:52kHz 电流 - 输出:1A 同步整流器:无 工作温度:-40°C ~ 125°C 安装类型:通孔 封装/外壳:16-DIP（0.300"，7.62mm） 包装:管件 供应商设备封装:16-DIP 其它名称:*LM2575HVN-12LM2575HVN-12 |
| MIC2172BM TR | 功能描述:IC REG MULTI CONFIG 1.25A 8SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:20 系列:SIMPLE SWITCHER® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:12V 输入电压:4 V ~ 60 V PWM 型:电压模式 频率 - 开关:52kHz 电流 - 输出:1A 同步整流器:无 工作温度:-40°C ~ 125°C 安装类型:通孔 封装/外壳:16-DIP（0.300"，7.62mm） 包装:管件 供应商设备封装:16-DIP 其它名称:*LM2575HVN-12LM2575HVN-12 |
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