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参数资料
| 型号： | LTC3548IMSE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ DL 10MSOP |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 2 |
| 输出电压： | 0.6 V ~ 5 V |
| 输入电压： | 2.5 V ~ 5.5 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 2.25MHz |
| 电流 - 输出： | 400mA，800mA |
| 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： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-MSOP 裸露焊盘 |
LTC3548
APPLICATIONS INFORMATION
The inductor value will also have an effect on Burst Mode
operation. The transition from low current operation
begins 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 to occur at lower
load currents. This causes 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
required. Several capacitors may also be paralleled to meet
the size or height requirements of the design. An additional
0.1μF to 1μF ceramic capacitor is also recommended on
V IN for high frequency decoupling, when not using an all
ceramic capacitor solution.
Table 1. Representation Surface Mount Inductors
PART VALUE DCR MAX DC SIZE
NUMBER (μH) (Ω MAX) CURRENT (A) W × L × H (mm 3 )
to increase.
Sumida
2.2
0.075
1.20
3.8 × 3.8 × 1.8
Inductor Core Selection
CDRH3D16
3.3
4.7
0.110
0.162
1.10
0.90
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 materials are
small and do not radiate much energy, but generally cost
more than powdered iron core inductors with similar elec-
trical 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
Sumida
CDRH2D11
Sumida
CMD4D11
Murata
LQH32CN
Toko
D312F
Panasonic
ELT5KT
1.5
2.2
2.2
3.3
1.0
2.2
2.2
3.3
3.3
4.7
0.068
0.170
0.116
0.174
0.060
0.097
0.060
0.260
0.17
0.20
0.900
0.780
0.950
0.770
1.00
0.079
1.08
0.92
1.00
0.95
3.2 × 3.2 × 1.2
4.4 × 5.8 × 1.2
2.5 × 3.2 × 2.0
2.5 × 3.2 × 2.0
4.5 × 5.4 × 1.2
LTC3548 requires to operate. Table 1 shows some typi-
cal surface mount inductors that work well in LTC3548
applications.
Input Capacitor (C IN ) Selection
In continuous mode, the input current of the converter is a
square wave with a duty cycle of approximately V OUT /V IN .
Output Capacitor (C OUT ) Selection
The selection of C OUT is driven by the required ESR to
minimize voltage ripple and load step transients. Typically,
once the ESR requirement is satis?ed, the capacitance
is adequate for ?ltering. The output ripple (ΔV OUT ) is
determined by:
Δ V OUT ≈ Δ I L ? ESR +
Topreventlargevoltagetransients,alowequivalentseries
resistance (ESR) input capacitor sized for the maximum
RMS current must be used. The maximum RMS capacitor
?
?
1 ?
8f O C OUT ? ?
current is given by:
where f = operating frequency, C OUT = output capacitance
I RMS ≈ I MAX
V OUT (V IN – V OUT )
V IN
and ΔI L = ripple current in the inductor. The output ripple
is highest at maximum input voltage since ΔI L increases
with input voltage. With ΔI L = 0.3 ? I OUT(MAX) the output
where the maximum average output current I MAX equals
the peak current minus half the peak-to-peak ripple cur-
rent, I MAX = I LIM – ΔI L /2.
This formula has a maximum at V IN = 2V OUT , where I RMS
= I OUT /2. This simple worst-case is commonly used to
design because even signi?cant deviations do not offer
much relief. Note that capacitor manufacturer’s ripple cur-
rent ratings are often based on only 2000 hours lifetime.
This makes it advisable to further derate the capacitor,
or choose a capacitor rated at a higher temperature than
8
ripple will be less than 100mV at maximum V IN and
f O = 2.25MHz with:
ESR COUT < 150mΩ
Once the ESR requirements for C OUT have been met, the
RMS current rating generally far exceeds the I RIPPLE(P-P)
requirement, except for an all ceramic solution.
In surface mount applications, multiple capacitors may
have to be paralleled to meet the capacitance, ESR or
RMS current handling requirement of the application.
Aluminum electrolytic, special polymer, ceramic and dry
3548fc
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