?/DIV>
I
f L
V
V
V
L
OUT
OUT
CC
1
1
1
(1)
The DC current rating of the inductor should be at least
equal to the maximum load current plus half the ripple
current to prevent core saturation. Thus, a 720mA rated
inductor should be enough for most applications (600mA
+ 120mA). For better efficiency, choose a low DC-resis-
tance inductor.
The inductor value also has an effect on Burst Mode
operation. The transition to low current operation begins
when the inductor current peaks fall to approximately
200mA. Lower inductor values (higher I
L
) will cause this
to occur at lower load currents, which can cause a dip in
efficiency in the upper range of low current operation. In
Burst Mode operation, lower inductance values will cause
the burst frequency to increase.
Inductor Core Selection
Different core materials and shapes will change the size/
current and price/current relationship of an inductor.
Toroid or shielded pot cores in ferrite or permalloy mate-
rials are small and dont radiate much energy, but gener-
ally cost more than powdered iron core inductors with
similar electrical characteristics. The choice of which style
inductor to use often depends more on the price vs size
requirements and any radiated field/EMI requirements
than on what the LTC3445 requires to operate. Table 1
shows some typical surface mount inductors that work
well in LTC3445 applications.
Table 1
MANUFACTURER   VALUE  DCR  MAX DC    SIZE
PART NUMBER
(?/SPAN>H) (m& MAX)  (A)  L ?/SPAN> W ?/SPAN> H (mm
3
)
Sumida CDRH3D16/   2.2    72    1.2   4.0 ?4.0 ?1.8
HP2R2
Sumida CR434R7    4.7   109    1.15   4.0 ?4.5 ?3.5
TDK TDK7030T-
2.2    12    5.5   7.3 ?6.8 ?3.2
2R2M5R4
Coilcraft D03316P-222  2.2    12
7  12.45 ?9.4 ?5.21
C
IN
and C
OUT
Selection
In continuous mode, the source current of the top MOSFET
is a square wave of duty cycle V
OUT
/V
CC1
. To prevent large
voltage transients, a low ESR input capacitor sized for the
maximum RMS current must be used. The maximum
RMS capacitor current is given by:
C
I
V  V  V
V
IN
OMAX
OUT CC   OUT
CC
required I
RMS
E
(    )
[
]
1
12
1
/
(2)
This formula has a maximum at V
CC1
= 2V
OUT
, where I
RMS
= I
OUT
/2. This simple worst-case condition is commonly
used for design because even significant deviations do not
offer much relief. Note that the capacitor manufacturers
ripple current ratings are often based on 2000 hours of life.
This makes it advisable to further derate the capacitor, or
choose a capacitor rated at a higher temperature than
required. Always consult the manufacturer if there is any
question.
The selection of C
OUT
is driven by the required effective
series resistance (ESR). Typically, once the ESR require-
ment for C
OUT
has been met, the RMS current rating
generally far exceeds the I
RIPPLE(P-P)
requirement. The
output ripple V
OUT
is determined by:
   E    +
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
V    I ESR
fC
OUT   L
OUT
1
8
(3)
相關代理商/技術參數 |
參數描述 |
LTC3446 |
制造商:LINER 制造商全稱:Linear Technology 功能描述:Monolithic Buck Regulator with Dual VLDO Regulators |
LTC3446EDE |
制造商:LINER 制造商全稱:Linear Technology 功能描述:Monolithic Buck Regulator with Dual VLDO Regulators |
LTC3446EDE#PBF |
功能描述:IC REG TRPL BCK/LINEAR 14-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩壓器 - 線性 + 切換式 系列:- 標準包裝:2,500 系列:- 拓撲:降壓(降壓)同步(3),線性(LDO)(2) 功能:任何功能 輸出數:5 頻率 - 開關:300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅動器:無 帶監控器:無 帶序列發生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應商設備封裝:* 包裝:* |
LTC3446EDE#TRPBF |
功能描述:IC REG TRPL BCK/LINEAR 14-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩壓器 - 線性 + 切換式 系列:- 標準包裝:2,500 系列:- 拓撲:降壓(降壓)同步(3),線性(LDO)(2) 功能:任何功能 輸出數:5 頻率 - 開關:300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅動器:無 帶監控器:無 帶序列發生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應商設備封裝:* 包裝:* |
LTC3446EDE-PBF |
制造商:LINER 制造商全稱:Linear Technology 功能描述:Monolithic Buck Regulator with Dual VLDO Regulators |
主站蜘蛛池模板:
长宁县|
曲阜市|
江山市|
吉水县|
西盟|
白水县|
句容市|
达拉特旗|
清苑县|
右玉县|
莲花县|
中西区|
宁明县|
黄平县|
湾仔区|
大足县|
桑日县|
上思县|
茂名市|
沛县|
綦江县|
镇康县|
永春县|
梧州市|
卓尼县|
沙河市|
铜陵市|
昌乐县|
台北市|
寿阳县|
武宁县|
昂仁县|
宝丰县|
堆龙德庆县|
卢氏县|
白河县|
贡嘎县|
兖州市|
建水县|
莱州市|
临海市|