參數(shù)資料
型號(hào)： MIC4684
廠商： Micrel Semiconductor,Inc.
元件分類： FPGA
英文描述： 150000 SYSTEM GATE 2.5 VOLT FPGA - NOT RECOMMENDED for NEW DESIGN
中文描述： 第2A高效SuperSwitcher降壓穩(wěn)壓器
文件頁(yè)數(shù)： 10/16頁(yè)
文件大?。?/td> 213K
代理商： MIC4684
MIC4684
Applications Information
Adjustable Regulators
Adjustable regulators require a 1.23V feedback signal. Rec-
ommended voltage-divider resistor values for common out-
put voltages are included in Table 1.
For other voltages, the resistor values can be determined
using the following formulas:
Micrel
MIC4684
10
July 2001
V
V
R1
R2
1
R1 R2
V
V
1
V
1.235V
OUT
REF
OUT
REF
REF
=
+
=
Minimum Pulse Width
The minimum duty cycle of the MIC4684 is approximately
10%. See Minimum Duty Cycle Graph If this input-to-output
voltage characteristic is exceeded, the MIC4684 will skip
cycles to maintain a regulated V
OUT
.
0
5
10
15
20
25
30
35
0
1
OUTPUT VOLTAGE (V)
2
3
4
5
6
M
Max. V
IN
for a Given V
OUT
for
Constant-Frequency Switching
Figure 1. Minimum Pulse Width Characteristic
Thermal Considerations
The MIC4684 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 MIC4684 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, and 7 and the
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
transfer through the ground leads to the printed circuit board.
One limitation of the maximum output current on any MIC4684
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 25
°
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 75
°
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
Make sure that MIC4684 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 MIC4684 as possible. The
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 2, 6, and 7 This ground plane area is more than sufficient
for most designs.
θ
JA
θ
JC
θ
CA
AMBENT
printed circuit board
ground plane
heat sink area
SOP-8
Figure 2. Power SOP-8 Cross Section
When designing with the MIC4684, 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 with V
IN
= 12V) and 60
°
C maximum ambient
temperature, what is the junction temperature
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
= 84%
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
0.84
5W
P
D
= 0.95W
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MIC4684_10 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:2A High-Efficiency SuperSwitcher Buck Regulator
MIC4684-3.3BM 功能描述:IC REG BUCK 3.3V 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(biāo)準(zhǔn)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
MIC4684-3.3BM TR 功能描述:IC REG BUCK 3.3V 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(biāo)準(zhǔn)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
MIC4684-5.0BM 功能描述:IC REG BUCK 5V 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(biāo)準(zhǔn)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
MIC4684-5.0BM TR 功能描述:IC REG BUCK 5V 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(biāo)準(zhǔn)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
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