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參數(shù)資料
| 型號： | MIC4685BR |
| 廠商： | MICREL INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3A SPAK SuperSwitcher⑩ Buck Regulator |
| 中文描述： | SWITCHING REGULATOR, 225 kHz SWITCHING FREQ-MAX, PSSO7 |
| 封裝： | SPAK-7 |
| 文件頁數(shù)： | 10/15頁 |
| 文件大?。?/td> | 154K |
| 代理商： | MIC4685BR |
MIC4685
Applications Information
Adjustable Regulators
Adjustable regulators require a 1.235V feedback signal.
Recommended voltage-divider resistor values for common
output voltages are included in Table 1.
For other voltages, the resistor values can be determined
using the following formulas:
Micrel
MIC4685
10
September 2002
V
V
R1
R2
1
R1 R2
V
V
1
V
1.235V
OUT
REF
OUT
REF
REF
=
+
=
Thermal Considerations
The MIC4685 is capable of high current due to the thermally
optimized SPAK package.
One limitation of the maximum output current on any MIC4685
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 2.2
°
C/W for a 7-lead SPAK.
θ
CA
is dependent on layout and is primarily governed by the
connection of pins 4, and Tab to the ground plane. The
purpose of the ground plane is to function as a heat sink.
Checking the Maximum Junction Temperature:
For this example, with an output power (P
OUT
) of 7.5W, (5V
output at 1.5A 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 1.5A 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 =7.5W
0.84
5W
7.
P
D
= 1.43W
A worst-case rule of thumb is to assume that 80% of the total
output power dissipation is in the MIC4685 (P
D(IC)
) and 20%
is in the diode-inductor-capacitor circuit.
P
D(IC)
= 0.8 P
D
P
D(IC)
= 0.8
×
1.43W
P
D(IC)
= 1.14W
Calculate the worst-case junction temperature:
T
J
= P
D(IC)
θ
JC
+ (T
C
–
T
A
) + T
A(max)
where:
T
J
= MIC4685 junction temperature
P
D(IC)
= MIC4685 power dissipation
θ
JC
= junction-to-case thermal resistance.
The
θ
JC
for the MIC4685
’
s 7-lead SPAK is approximately
2.2
°
C/W.
T
C
=
“
pin
”
temperature measurement taken at the
Tab.
T
A
= ambient temperature
T
A(max)
= maximum ambient operating temperature
for the specific design.
Calculating the maximum junction temperature given a
maximum ambient temperature of 60
°
C:
T
J
= 1.14
×
2.2
°
C + (46
°
C
–
25
°
C) + 60
°
C
T
J
= 83.5
°
C
This value is within the allowable maximum operating junc-
tion temperature of 125
°
C as listed in
“
Operating Ratings.
”
Typical thermal shutdown is 160
°
C and is listed in Electrical
Characteristics Also see Typical Safe Operating Area SOA)
graphs on page 7.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MIC4685BR TR | 功能描述:IC REG BUCK ADJ 3A SPAK-7 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 |
| MIC4685BRTR | 制造商:Rochester Electronics LLC 功能描述:- Tape and Reel |
| MIC4685WR | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3A Buck Regulator in SPAK-7 (ROHS Compliant) 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 |
| MIC4685WR TR | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3A Buck Regulator in SPAK-7 (ROHS Compliant) 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 |
| MIC4685WREV | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:3A SPAK SuperSwitcher Buck Regulator |
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