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参数资料
| 型号： | MIC4681YM TR |
| 厂商： | Micrel Inc |
| 文件页数： | 12/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1A 8SOIC |
| 标准包装： | 2,500 |
| 系列： | SuperSwitcher™ |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 可调至 1.25V |
| 输入电压： | 4 V ~ 30 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 200kHz |
| 电流 - 输出： | 1A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-SOIC |
| 其它名称： | MIC4681YMTR MIC4681YMTR-ND |
MIC4681
Thermal Considerations
The MIC4681 SuperSwitcher ? features the power-SOP-8.
This package has a standard 8-lead small-outline package
profile, but with much higher power dissipation than a stan-
dard SOP-8. Micrel's MIC4681 SuperSwitcher ? family are
Micrel
Minimum Copper/Maximum Current Method
Using Figure 3, for a given input voltage range, determine the
minimum ground-plane heat-sink area required for the
application ’ s maximum continuous output current. Figure 3
assumes a constant die temperature of 75 ° C above ambient.
the first dc-to-dc converters to take full advantage of this
package.
1.5
8V
12V
The reason that the power SOP-8 has higher power dissipa-
tion (lower thermal resistance) is that pins 5 through 8 and the
1.0
24V
die-attach paddle are a single piece of metal. The die is
attached to the paddle with thermally conductive adhesive.
This provides a low thermal resistance path from the junction
of the die to the ground pins. This design significantly im-
proves package power dissipation by allowing excellent heat
0.5
V IN = 30V
T A = 50 ° C
transfer through the ground leads to the printed circuit board.
0
0
5
10
15
20
25
One limitation of the maximum output current on any MIC4681
design is the junction-to-ambient thermal resistance ( θ JA ) of
the design (package and ground plane).
Examining θ JA in more detail:
θ JA = ( θ JC + θ CA )
where:
θ JC = junction-to-case thermal resistance
θ CA = case-to-ambient thermal resistance
θ JC is a relatively constant 20 ° C/W for a power SOP-8.
θ CA is dependent on layout and is primarily governed by the
connection of pins 5 though 8 to the ground plane. The
purpose of the ground plane is to function as a heat sink.
θ JA is ideally 63 ° C/W, but will vary depending on the size of
the ground plane to which the power SOP-8 is attached.
Determining Ground-Plane Heat-Sink Area
There are two methods of determining the minimum ground
AREA (cm 2 )
Figure 3. Output Current vs. Ground Plane Area
When designing with the MIC4681, it is a good practice to
connect pins 5 through 8 to the largest ground plane that is
practical for the specific design.
Checking the Maximum Junction Temperature:
For this example, with an output power (P OUT ) of 5W, (5V
output at 1A maximum with V IN = 12V) and 65 ° C maximum
ambient temperature, what is the maximum junction tem-
perature?
Referring to the “ Typical Characteristics: 5V Output Effi-
ciency ” graph, read the efficiency ( η ) for 1A output current at
V IN = 12V or perform you own measurement.
η = 79%
The efficiency is used to determine how much of the output
power (P OUT ) is dissipated in the regulator circuit (P D ).
plane area required by the MIC4681.
Quick Method
Make sure that MIC4681 pins 5 though 8 are connected to a
ground plane with a minimum area of 6cm 2 . This ground
plane should be as close to the MIC4681 as possible. The
P D =
P D =
P OUT
η
5W
0.79
? P OUT
? 5W
area may be distributed in any shape around the package or
on any pcb layer as long as there is good thermal contact to
pins 5 though 8. This ground plane area is more than
sufficient for most designs.
SOP-8
P D = 1.33W
A worst-case rule of thumb is to assume that 80% of the total
output power dissipation is in the MIC4681 (P D(IC) ) and 20%
is in the diode-inductor-capacitor circuit.
P D(IC) = 0.8 P D
P D(IC) = 0.8 × 1.33W
P D(IC) = 1.064W
Calculate the worst-case junction temperature:
T J = P D(IC) θ JC + (T C – T A ) + T A(max)
where:
BIE
θ JC
θ JA
θ CA
AM
NT
ground plane
heat sink area
T J = MIC4681 junction temperature
P D(IC) = MIC4681 power dissipation
θ JC = junction-to-case thermal resistance.
The θ JC for the MIC4681 ’ s power-SOP-8 is approximately
20 ° C/W.
printed circuit board
Figure 2. Power SOP-8 Cross Section
T C = “ pin ” temperature measurement taken at the
entry point of pins 6 or 7
MIC4681
12
April 2005
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| MIC4682 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:PRECISION CURRENT LIMIT SO-8 SUPERSWITCHER BUCK REGULATOR |
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| MIC4682BM | 功能描述:IC REG BUCK 2A 8SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:SuperSwitcher™ 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 |
| MIC4682BM TR | 功能描述:IC REG BUCK 2A 8SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:SuperSwitcher™ 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 |
| MIC4682YM | 功能描述:直流/直流开关调节器 Precision Current Limit SO-8 Super Switcher (Lead Free) RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
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