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參數(shù)資料
| 型號： | MIC4682BM |
| 廠商： | MICREL INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | PRECISION CURRENT LIMIT SO-8 SUPERSWITCHER BUCK REGULATOR |
| 中文描述： | 1.1 A SWITCHING REGULATOR, 220 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | SOIC-8 |
| 文件頁數(shù)： | 11/15頁 |
| 文件大?。?/td> | 226K |
| 代理商： | MIC4682BM |
October 2003
11
M0334-102203
MIC4682
Thermal Considerations
The MIC4682 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 MIC4682 SuperSwitcher
family are
the first DC-to-DC converters to take full advantage of this
package.
The reason that the power SOP-8 has higher power dissipa-
tion (lower thermal resistance) is that pins 2, 6, 7 and the die-
attach paddle are a single piece of metal. The die is attached
to the paddle with thermally conductive adhesive. This pro-
vides a low thermal resistance path from the junction of the
die to the ground pins. This design significantly improves
package power dissipation by allowing excellent heat trans-
fer through the ground leads to the printed circuit board.
One limitation of the maximum output current on any MIC4682
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 2, 6 and 7 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
plane area required by the MIC4682.
Quick Method
Make sure that MIC4682 pins 2, 6 and 7 are connected to a
ground plane with a minimum area of 6cm
2
. This ground
plane should be as close to the MIC4682 as possible. The
area may be distributed in any shape around the package or
on any PCB layer as ong as here s good hermal contact o
Micrel
pins 2, 6 and 7 This ground plane area is more than sufficient
for most designs.
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.
0
0.5
1.0
1.5
0
5
10
AREA (cm
2
)
15
20
25
C
12V
8V
V
IN
= 30V
24V
T
A
= 50
°
C
Figure 3. Output Current vs. Ground Plane Area
When designing with the MIC4682, it is a good practice to
connect pins 2, 6 and 7 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: Efficiency vs. Out-
put Current
”
graph, read the efficiency (
η
) for 1A output
current at V
IN
= 12V or perform you own measurement.
η
= 81%
The efficiency is used to determine how much of the output
power (P
OUT
) is dissipated in the regulator circuit (P
D
).
P =P
P
OUT
η
OUT
P =5W
0.81
5W
P
D
= 1.17W
A worst-case rule of thumb is to assume that 80% of the total
output power dissipation is in the MIC4682 (P
D(IC)
) and 20%
is in the diode-inductor-capacitor circuit.
P
D(IC)
= 0.8 P
D
P
D(IC)
= 0.8
×
1.17W
P
D(IC)
= 0.936W
Calculate the worst-case junction temperature:
T
J
= P
D(IC)
θ
JC
+ (T
C
–
T
A
) + T
A(max)
where:
T
J
= MIC4682 junction temperature
P
D(IC)
= MIC4682 power dissipation
θ
JC
= junction-to-case thermal resistance.
The
θ
JC
for the MIC4682
’
s power-SOP-8 is approximately
20
°
C/W.
θ
JA
θ
JC
θ
CA
AMBENT
printed circuit board
ground plane
heat sink area
SOP-8
Figure 2. Power SOP-8 Cross Section
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| MIC4682BM TR | 功能描述:IC REG BUCK 2A 8SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:SuperSwitcher™ 標準包裝:20 系列:SIMPLE SWITCHER® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:12V 輸入電壓:4 V ~ 60 V PWM 型:電壓模式 頻率 - 開關(guān):52kHz 電流 - 輸出:1A 同步整流器:無 工作溫度:-40°C ~ 125°C 安裝類型:通孔 封裝/外殼:16-DIP（0.300"，7.62mm） 包裝:管件 供應(yīng)商設(shè)備封裝:16-DIP 其它名稱:*LM2575HVN-12LM2575HVN-12 |
| MIC4682YM | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 Precision Current Limit SO-8 Super Switcher (Lead Free) RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| MIC4682YM TR | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 Precision Current Limit SO-8 Super Switcher (Lead Free) RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
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