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參數(shù)資料
| 型號(hào)： | LTC3407AEDD#TR |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1.25 A DUAL SWITCHING CONTROLLER, 1800 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封裝： | 3 X 3 MM, PLASTIC, MO-229WEED-2, DFN-10 |
| 文件頁(yè)數(shù)： | 15/16頁(yè) |
| 文件大?。?/td> | 263K |
| 代理商： | LTC3407AEDD#TR |
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LTC3407A
8
3407af
Input Capacitor (CIN) Selection
In continuous mode, the input current of the converter is
a square wave with a duty cycle of approximately VOUT/
VIN. To prevent large voltage transients, a low equivalent
series resistance (ESR) input capacitor sized for the maxi-
mum RMS current must be used. The maximum RMS
capacitor current is given by:
II
VV
V
RMS
MAX
OUT
IN
OUT
IN
≈
(–
)
where the maximum average output current IMAX equals
the peak current minus half the peak-to-peak ripple cur-
rent, IMAX = ILIM – IL/2.
This formula has a maximum at VIN = 2VOUT, where IRMS
= IOUT/2. This simple worst-case is commonly used to
design because even significant deviations do not offer
much relief. Note that capacitor manufacturer’s ripple
current ratings are often based on only 2000 hours life-
time. This makes it advisable to further derate the capaci-
tor, or choose a capacitor rated at a higher temperature
than required. Several capacitors may also be paralleled to
meet the size or height requirements of the design. An
additional 0.1
F to 1F ceramic capacitor is also recom-
mended on VIN for high frequency decoupling, when not
using an all ceramic capacitor solution.
Table 1. Representative Surface Mount Inductors
MANU-
MAX DC
FACTURER
PART NUMBER
VALUE CURRENT
DCR
HEIGHT
Taiyo Yuden CB2016T2R2M
2.2
H
510mA
0.13
1.6mm
CB2012T2R2M
2.2
H
530mA
0.33
1.25mm
CB2016T3R3M
3.3
H
410mA
0.27
1.6mm
Panasonic
ELT5KT4R7M
4.7
H
950mA
0.2
1.2mm
Sumida
CDRH2D18/LD
4.7
H
630mA
0.086
2mm
Murata
LQH32CN4R7M23 4.7
H
450mA
0.2
2mm
Taiyo Yuden NR30102R2M
2.2
H
1100mA
0.1
1mm
NR30104R7M
4.7
H
750mA
0.19
1mm
FDK
FDKMIPF2520D
4.7
H
1100mA
0.11
1mm
FDKMIPF2520D
3.3
H
1200mA
0.1
1mm
FDKMIPF2520D
2.2
H
1300mA
0.08
1mm
TDK
VLF3010AT4R7-
4.7
H
700mA
0.28
1mm
MR70
VLF3010AT3R3-
3.3
H
870mA
0.17
1mm
MR87
VLF3010AT2R2-
2.2
H
1000mA
0.12
1mm
M1R0
APPLICATIO S I FOR ATIO
WU
U
Inductor Selection
Although the inductor does not influence the operating
frequency, the inductor value has a direct effect on ripple
current. The inductor ripple current
IL decreases with
higher inductance and increases with higher VIN or VOUT:
=
I
V
fL
V
L
OUT
O
OUT
IN
–
1
Accepting larger values of
IL allows the use of low
inductances, but results in higher output voltage ripple,
greater core losses, and lower output current capability.
A reasonable starting point for setting ripple current is
IL = 0.3 ILIM, where ILIM is the peak switch current limit.
The largest ripple current
IL occurs at the maximum
input voltage. To guarantee that the ripple current stays
below a specified maximum, the inductor value should be
chosen according to the following equation:
L
V
fI
V
OUT
OL
OUT
IN MAX
=
–
()
1
The inductor value will also have an effect on Burst Mode
operation. The transition from low current operation be-
gins when the peak inductor current falls below a level set
by the burst clamp. Lower inductor values result in higher
ripple current which causes this transition to occur at
lower load currents. This causes 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 don’t radiate much energy, but gener-
ally cost more than powdered iron core inductors with
similar electrical characterisitics. The choice of which
style inductor to use often depends more on the price vs
size requirements and any radiated field/EMI require-
ments than on what the LTC3407A requires to operate.
Table 1 shows some typical surface mount inductors that
work well in LTC3407A applications.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3407AEDD-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Dual Synchronous 600mA, 1.5MHz Step-Down DC/DC Regulator |
| LTC3407AEMSE#PBF | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)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(kāi)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(yīng)商設(shè)備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁(yè)面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2 |
| LTC3407AEMSE#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)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(kāi)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(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LTC3407AEMSE-2 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Dual Synchronous 800mA,2.25MHz Step-Down DC/DC Regulator |
| LTC3407AEMSE-2#PBF | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)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(kāi)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(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
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