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| 型号： | LT3957EUHE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 20/28页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG ADJ 36VQFN |
| 特色产品： | LT?3957/LT?3958 Converters |
| 标准包装： | 61 |
| 类型： | 升压（升压），反相，回扫，Sepic |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.6 V ~ 40 V |
| 输入电压： | 3 V ~ 40 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 100kHz ~ 1MHz |
| 电流 - 输出： | 5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 36-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 36-QFN-EP（6x5） |
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LT3957
APPLICATIONS INFORMATION
V IN(MIN)
Δ I SW ? ?
BymakingL1=L2,andwindingthemonthesamecore,the
value of inductance in the preceding equation is replaced
by 2L, due to mutual inductance:
L = ? D MAX
This maintains the same ripple current and energy storage
in the inductors. The peak inductor currents are:
I L1(PEAK) = I L1(MAX) + 0.5 ? Δ I L1
I L2(PEAK) = I L2(MAX) + 0.5 ? Δ I L2
The maximum RMS inductor currents are approximately
equal to the maximum average inductor currents.
Based on the preceding equations, the user should choose
the inductors having suf?cient saturation and RMS cur-
rent ratings.
SEPIC Converter: Output and Input Capacitor Selection
The selections of the output and input capacitors of the
SEPIC converter are similar to those of the boost converter.
Please refer to the Boost Converter: Output Capacitor
Selection and Boost Converter: Input Capacitor Selection
sections.
SEPIC Converter: Selecting the DC Coupling Capacitor
The DC voltage rating of the DC coupling capacitor (C DC ,
as shown in Figure 1) should be larger than the maximum
input voltage:
V CDC > V IN(MAX)
C DC has nearly a rectangular current waveform. During
the switch off-time, the current through C DC is I IN , while
approximately –I O ?ows during the on-time. The RMS
rating of the coupling capacitor is determined by the fol-
lowing equation:
SEPIC Converter: Output Diode Selection
To maximize ef?ciency, a fast switching diode with a low
forward drop and low reverse leakage is desirable. The
I RMS(CDC) > I O(MAX) ?
V OUT + V D
V IN(MIN)
average forward current in normal operation is equal to
the output current.
It is recommended that the peak repetitive reverse voltage
rating V RRM is higher than V OUT + V IN(MAX) by a safety
margin (a 10V safety margin is usually suf?cient).
The power dissipated by the diode is:
A low ESR and ESL, X5R or X7R ceramic capacitor works
well for C DC .
INVERTING CONVERTER APPLICATIONS
The LT3957 can be con?gured as a dual-inductor inverting
topology, as shown in Figure 8. The V OUT to V IN ratio is:
P D = I O(MAX) ? V D
where V D is diode’s forward voltage drop, and the diode
junction temperature is:
V OUT ? V D
V IN
=?
D
1 ? D
T J = T A + P D ? R θ JA
in continuous conduction mode (CCM).
The R θ JA used in this equation normally includes the R θ JC
for the device, plus the thermal resistance from the board,
to the ambient temperature in the enclosure. T J must not
exceed the diode maximum junction temperature rating.
V IN
+
C IN
L1
SW
C DC
+
–
L2
C OUT
+
–
V OUT
LT3957
GND
D1
+
3757 F10
Figure 8. A Simpli?ed Inverting Converter
3957f
20
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3957EUHETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch |
| LT3957IUHE#PBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°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 |
| LT3957IUHE#TRPBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°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 |
| LT3957IUHEPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch |
| LT3957IUHETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch |
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