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参数资料
| 型号： | LTC3549EDCB#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 9/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 0.25A 6DFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.61 V ~ 5.5 V |
| 输入电压： | 1.6 V ~ 5.5 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 2.25MHz |
| 电流 - 输出： | 250mA |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 6-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 6-DFN-EP（2x3） |
LTC3549
OPERATION
be de?ned by the combination of the current needed to
charge the output capacitance and the current provided
to the load as the output voltage ramps up. The start-up
APPLICATIO S I FOR ATIO
The basic LTC3549 application circuit is shown on the ?rst
page of this data sheet. External component selection is
driven by the load requirement and begins with the selection
of L followed by C IN and C OUT .
Inductor Selection
For most applications, the value of the inductor will fall
in the range of 1μH to 10μH. Its value is chosen based
on the desired ripple current. Large value inductors
lower ripple current and small value inductors result in
waveform, shown in the Typical Performance Character-
istics, shows the output voltage start-up from 0V to 1.2V
with a 1k Ω load and V IN = 3.6V.
materials are small and don’t radiate much energy, but
generally 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 ?eld/EMI requirements
than on what the LTC3549 requires to operate. Table 1
shows some typical surface mount inductors that work
well in LTC3549 applications.
Table 1. Representative Surface Mount Inductors
higher ripple currents. Higher V IN or V OUT also increases
the ripple current as shown in Equation 1. A reasonable
MANU-
FACTURER
PART NUMBER
MAX DC
VALUE CURRENT
(μH) (A)
DCR
HEIGHT
(mm)
starting point for setting ripple current is Δ I L = 100mA
Taiyo
LB2016T2R2M
2.2
315
0.13
1.6
V OUT ? V OUT ?
? ? 1 – V
? I L =
IN ?
(40% of 250mA).
f ? L ?
(1)
Yuden
Panasonic
Murata
LB2012T2R2M
LB2016T3R3M
LB2016T4R7M
ELT5KT4R7M
LQH32CN4R7M34
2.2
3.3
4.7
4.7
4.7
240
280
210
950
450
0.23
0.2
0.25
0.2
0.2
1.25
1.6
1.6
1.2
2
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 300mA rated
inductor should be enough for most applications (250mA
+ 50mA). For better ef?ciency, choose a low DC resistance
TDK
VLF3012AT2R2M1R0
VLF3012AT3R3MR87
VLF3012AT4R7MR74
VLF3010AT2R2M1R0
VLF3010AT3R3MR87
VLF3010AT4R7MR70
2.2
3.3
4.7
2.2
3.3
4.7
1
0.87
0.74
1
0.87
0.74
0.088
0.11
0.16
0.10
0.15
0.24
1.2
1.2
1.2
1.0
1.0
1.0
inductor. The inductor value also has an effect on Burst
[ V OUT ( V IN – V OUT ) ]
Modeoperation.Thetransitiontolowcurrentoperationbe-
gins when the inductor current peaks fall to approximately
100mA. Lower inductor values (higher Δ I L ) will cause this
to occur at lower load currents, which can cause a dip in
ef?ciency 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 induc-
tor. Toroid or shielded pot cores in ferrite or permalloy
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 IN . 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:
1 / 2
C IN Re quired I RMS ? I OUT ( MAX )
V IN
This formula has a maximum at V IN = 2V OUT , where
I RMS = I OUT /2. This simple worst-case condition is com-
monly used for design because even significant devia-
3549f
9
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| LTC3550EDHC#PBF | 功能描述:IC CHARGER BATT DUAL 16-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:61 系列:- 功能:电源管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:4.35 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:22-WFDFN 裸露焊盘 供应商设备封装:22-DFN（6x3）裸露焊盘 包装:管件 |
| LTC3550EDHC#TRPBF | 功能描述:IC CHARGER BATT DUAL 16-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:61 系列:- 功能:电源管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:4.35 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:22-WFDFN 裸露焊盘 供应商设备封装:22-DFN（6x3）裸露焊盘 包装:管件 |
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