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参数资料
| 型号： | LTC3404MPMS8#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 0.6A 8MSOP |
| 标准包装： | 50 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.8 V ~ 6 V |
| 输入电压： | 2.65 V ~ 6 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 1.4MHz |
| 电流 - 输出： | 600mA |
| 同步整流器： | 是 |
| 工作温度： | -55°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 包装： | 管件 |
| 供应商设备封装： | 8-MSOP |
LTC3404
APPLICATIO S I FOR ATIO
[ V OUT ( V IN ? V OUT ) ] 1 / 2
V OUT = 0 . 8 V ? 1 +
?
?
R 1 ?
inductor ripple current and consequent output voltage
ripple. Do not allow the core to saturate!
Kool M μ (from Magnetics, Inc.) is a very good, low loss
core material for toroids with a “soft” saturation character-
istic. Molypermalloy is slightly more efficient at high
(>200kHz) switching frequencies but quite a bit more
expensive. Toroids are very space efficient, especially
when you can use several layers of wire, while inductors
wound on bobbins are generally easier to surface mount.
New designs for surface mount inductors are available
from Coiltronics, Coilcraft, Dale and Sumida.
C IN and C OUT Selection
In continuous mode, the source current of the top MOS-
FET 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 maxi-
mum RMS capacitor current is given by:
C IN required I RMS ? I OMAX
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 deviations
do not offer much relief. Note that the capacitor
manufacturer’s 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. Several capacitors may also be
paralleled to meet size or height requirements in the
design. 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 is satisfied, the capacitance is adequate for filtering.
The output ripple Δ V OUT is determined by:
is highest at maximum input voltage since Δ I L increases
with input voltage. For the LTC3404, the general rule for
proper operation is:
C OUT required ESR < 0.25 Ω
The choice of using a smaller output capacitance
increases the output ripple voltage due to the frequency
dependent term but can be compensated for by using
capacitor(s) of very low ESR to maintain low ripple
voltage. The I TH pin compensation components can be
optimized to provide stable high performance transient
response regardless of the output capacitor selected.
ESR is a direct function of the volume of the capacitor.
Manufacturers such as Taiyo-Yuden, AVX, Kemet, Sprague
and Sanyo should be considered for high performance
capacitors. The POSCAP solid electrolytic chip capacitor
available from Sanyo is an excellent choice for output bulk
capacitors due to its low ESR/size ratio. Once the ESR
requirement for C OUT has been met, the RMS current
rating generally far exceeds the I RIPPLE(P-P) requirement.
When using tantalum capacitors, it is critical that they are
surge tested for use in switching power supplies. A good
choice is the AVX TPS series of surface mount tantalum,
available in case heights ranging from 2mm to 4mm. Other
capacitor types include KEMET T510 and T495 series and
Sprague 593D and 595D series. Consult the manufacturer
for other specific recommendations.
Output Voltage Programming
The output voltage is set by a resistive divider according
to the following formula:
? R 2 ?
(2)
The external resistive divider is connected to the output,
allowing remote voltage sensing as shown in Figure 3.
0.8V ≤ V OUT ≤ 6V
? Δ I L ? ESR +
8 fC OUT ?
Δ V OUT
?
?
1 ?
?
LTC3404
V FB
R2
R1
where f = operating frequency, C OUT = output capacitance
and Δ I L = ripple current in the inductor. The output ripple
GND
3404 F03
Figure 3. Setting the LTC3404 Output Voltage
3404fb
10
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相关代理商/技术参数 |
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|---|---|
| LTC3405 | 制造商:LINEAR 制造商全称:LINEAR 功能描述:Standalone 250mA Li-Ion Battery Charger in 2 × 2 DFN |
| LTC3405A | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.5MHz, 300mA Synchronous Step-Down Regulator in ThinSOT |
| LTC3405A-1.375 | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.375V, 1.5MHz, 300mA Synchronous Step-Down Regulators in ThinSOT |
| LTC3405A-1.5 | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.5V, 1.8V, 1.5MHz, 300mA Synchronous Step-Down Regulators in ThinSOT |
| LTC3405A-1.8 | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.5V, 1.8V, 1.5MHz, 300mA Synchronous Step-Down Regulators in ThinSOT |
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