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參數(shù)資料
| 型號： | LTC3411EMS |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1.25A, 4MHz, Synchronous Step-Down DC/DC Converter |
| 中文描述： | 2 A SWITCHING REGULATOR, 4000 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封裝： | PLASTIC, MSOP-10 |
| 文件頁數(shù)： | 14/20頁 |
| 文件大?。?/td> | 288K |
| 代理商： | LTC3411EMS |
LTC3411
14
sn3411 3411fs
Thermal Considerations
In a majority of applications, the LTC3411 does not
dissipate much heat due to its high efficiency. However, in
applications where the LTC3411 is running at high ambi-
ent temperature with low supply voltage and high duty
cycles, such as in dropout, the heat dissipated may exceed
the maximum junction temperature of the part. If the
junction temperature reaches approximately 150
°
C, both
power switches will be turned off and the SW node will
become high impedance.
To avoid the LTC3411 from exceeding the maximum
junction temperature, the user will need to do some
thermal analysis. The goal of the thermal analysis is to
determine whether the power dissipated exceeds the
maximum junction temperature of the part. The tempera-
ture rise is given by:
T
RISE
= P
D
θ
JA
where P
D
is the power dissipated by the regulator and
θ
JA
is the thermal resistance from the junction of the die to the
ambient temperature.
The junction temperature, T
J
, is given by:
T
J
= T
RISE
+ T
AMBIENT
As an example, consider the case when the LTC3411 is in
dropout at an input voltage of 3.3V with a load current of
1A. From the Typical Performance Characteristics graph
of Switch Resistance, the R
DS(ON)
resistance of the
P-channel switch is 0.11
. Therefore, power dissipated
by the part is:
P
D
= I
2
R
DS(ON)
= 110mW
The MS10 package junction-to-ambient thermal resis-
tance,
θ
JA
, will be in the range of 100
°
C/W to 120
°
C/W.
Therefore, the junction temperature of the regulator oper-
ating in a 70
°
C ambient temperature is approximately:
T
J
= 0.11 120 + 70 = 83.2
°
C
Remembering that the above junction temperature is
obtained from an R
DS(ON)
at 25
°
C, we might recalculate
the junction temperature based on a higher R
DS(ON)
since
it increases with temperature. However, we can safely
APPLICATIU
W
U
U
assume that the actual junction temperature will not
exceed the absolute maximum junction temperature of
125
°
C.
Design Example
As a design example, consider using the LTC3411 in a
portable application with a Li-Ion battery. The battery
provides a V
IN
= 2.5V to 4.2V. The load requires a maxi-
mum of 1A in active mode and 10mA in standby mode. The
output voltage is V
OUT
= 2.5V. Since the load still needs
power in standby, Burst Mode operation is selected for
good low load efficiency.
First, calculate the timing resistor:
R
MHz
1
k
T
=
(
)
=
9 78 10
.
323 8
11
1 08
.
.
Use a standard value of 324k. Next, calculate the inductor
value for about 30% ripple current at maximum V
IN
:
L
V
MHz
1
mA
V
V
H
=
= μ
2 5
.
510
1
2 5
4 2
.
2
.
Choosing the closest inductor from a vendor of 2.2
μ
H,
results in a maximum ripple current of:
=
μ
=
I
V
2 2
MHz
1
V
V
mA
L
2 5
.
1
2 5
4 2
.
460
.
For cost reasons, a ceramic capacitor will be used. C
OUT
selection is then based on load step droop instead of ESR
requirements. For a 5% output droop:
C
A
5
MHz
1
V
F
OUT
≈
=
μ
2 5
.
1
20
( %2 5
)
The closest standard value is 22
μ
F. Since the output
impedance of a Li-Ion battery is very low, C
IN
is typically
10
μ
F. In noisy environments, decoupling SV
IN
from PV
IN
with an R6/C8 filter of 1
/0.1
μ
F may help, but is typically
not needed.
The output voltage can now be programmed by choosing
the values of R1 and R2. To maintain high efficiency, the
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| LTC3411EMS#PBF | 功能描述:IC REG BUCK SYNC ADJ 10MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標準包裝:250 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V 輸入電壓:2.05 V ~ 6 V PWM 型:電壓模式 頻率 - 開關(guān):2MHz 電流 - 輸出:500mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:6-UFDFN 包裝:帶卷 (TR) 供應商設(shè)備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2 |
| LTC3411EMS#PBFTR | 制造商:Linear Technology 功能描述:Conv DC-DC Single Step Down 2.63V to 5.5V 10-Pin MSOP T/R |
| LTC3411EMS#TR | 功能描述:IC REG BUCK SYNC ADJ 10MSOP 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:- 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LTC3411EMS#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 10MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應商設(shè)備封裝:10-MSOP 裸露焊盤 |
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