参数资料
型号: LT3757EDD#PBF
厂商: Linear Technology
文件页数: 17/36页
文件大小: 0K
描述: IC REG CTRLR BST FLYBK INV 10DFN
产品培训模块: LT3757 and LT3758 - Boost, Flyback, SEPIC and Inverting Controllers
特色产品: LT3757 - Inverting Controller
标准包装: 121
PWM 型: 电流模式
输出数: 1
频率 - 最大: 1MHz
电源电压: 2.9 V ~ 40 V
降压:
升压:
回扫:
反相:
倍增器:
除法器:
Cuk:
隔离:
工作温度: -40°C ~ 125°C
封装/外壳: 10-WFDFN 裸露焊盘
包装: 管件
产品目录页面: 1332 (CN2011-ZH PDF)
LT3757/LT3757A
APPLICATIONS INFORMATION
C OUT ≥
I RMS(COUT) ≥ I O(MAX) ?
RCD SNUBBER
N P :N S
+
+
V SN +
+
+
V DS
ForthebulkCcomponent,whichalsocontributes1%to
the total ripple:
I O(MAX)
0.01 ? V OUT ? f
The output capacitor in a boost regulator experiences high
RMS ripple currents, as shown in Figure 6. The RMS ripple
current rating of the output capacitor can be determined
using the following equation:
D MAX
1 ? D MAX
Multiple capacitors are often paralleled to meet ESR
requirements. Typically, once the ESR requirement is
satisfied, the capacitance is adequate for filtering and has
the required RMS current rating. Additional ceramic capaci-
tors in parallel are commonly used to reduce the effect of
parasitic inductance in the output capacitor, which reduces
high frequency switching noise on the converter output.
Boost Converter: Input Capacitor Selection
The input capacitor of a boost converter is less critical
than the output capacitor, due to the fact that the inductor
is in series with the input, and the input current wave-
form is continuous. The input voltage source impedance
determines the size of the input capacitor, which is typi-
cally in the range of 10μF to 100μF. A low ESR capacitor
is recommended, although it is not as critical as for the
output capacitor.
The RMS input capacitor ripple current for a boost con-
verter is:
FLYBACK CONVERTER APPLICATIONS
The LT3757 can be configured as a flyback converter
for the applications where the converters have multiple
outputs, high output voltages or isolated outputs. Figure
7 shows a simplified flyback converter.
The flyback converter has a very low parts count for mul-
tiple outputs, and with prudent selection of turns ratio, can
have high output/input voltage conversion ratios with a
desirable duty cycle. However, it has low efficiency due to
the high peak currents, high peak voltages and consequent
power loss. The flyback converter is commonly used for
an output power of less than 50W.
The flyback converter can be designed to operate either
in continuous or discontinuous mode. Compared to con-
tinuous mode, discontinuous mode has the advantage of
smaller transformer inductances and easy loop compen-
sation, and the disadvantage of higher peak-to-average
current and lower efficiency. In the high output voltage
applications, the flyback converters can be designed
to operate in discontinuous mode to avoid using large
transformers.
SUGGESTED
D
V IN
C IN C SN R SN I D
L P L S C OUT
D SN
I SW
LT3757
GATE M
SENSE –
I RMS(CIN) = 0.3 ? ? I L
GND
R SENSE
3757 F06
Figure 7. A Simplified Flyback Converter
3757afd
17
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LT3757EMSE#PBF 制造商:Linear Technology 功能描述:DC-DC CONTROLLER SEPIC 1MHZ 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, SEPIC, 1MHZ, MSOP-10
LT3757EMSE#TRPBF 功能描述:IC REG CTRLR PWM CM 10-MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR)