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参数资料
| 型号： | LT3757IDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/36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 |
| 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： | 无 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 是 |
| 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： | 10-WFDFN 裸露焊盘 |
| 包装： | 管件 |
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LT3757/LT3757A
APPLICATIONS INFORMATION
? V SENSE
80mV ? 0.5 ? ? V SENSE
V OUT 1
1 ? D
V IN
D MAX =
DuetothecurrentlimitfunctionoftheSENSEpin,R SENSE
should be selected to guarantee that the peak current sense
voltage V SENSE(PEAK) during steady state normal operation
is lower than the SENSE current limit threshold (see the
Electrical Characteristics table). Given a 20% margin,
V SENSE(PEAK) is set to be 80mV. Then, the maximum
switch ripple current percentage can be calculated using
the following equation:
c=
c is used in subsequent design examples to calculate in-
ductor value. ?V SENSE is the ripple voltage across R SENSE .
The LT3757 switching controller incorporates 100ns timing
interval to blank the ringing on the current sense signal
immediately after M1 is turned on. This ringing is caused
by the parasitic inductance and capacitance of the PCB
trace, the sense resistor, the diode, and the MOSFET. The
100ns timing interval is adequate for most of the LT3757
applications. In the applications that have very large and
long ringing on the current sense signal, a small RC filter
can be added to filter out the excess ringing. Figure 5
shows the RC filter on SENSE pin. It is usually sufficient
to choose 22Ω for R FLT and 2.2nF to 10nF for C FLT .
Keep R FLT ’s resistance low. Remember that there is 65μA
(typical) flowing out of the SENSE pin. Adding R FLT will
affect the SENSE current limit threshold:
V SENSE_ILIM = 108mV – 65μA ? R FLT
APPLICATION CIRCUITS
The LT3757 can be configured as different topologies. The
first topology to be analyzed will be the boost converter,
followed by the flyback, SEPIC and inverting converters.
Boost Converter: Switch Duty Cycle and Frequency
The LT3757 can be configured as a boost converter for
the applications where the converter output voltage is
higher than the input voltage. Remember that boost con-
verters are not short-circuit protected. Under a shorted
output condition, the inductor current is limited only by
the input supply capability. For applications requiring a
step-up converter that is short-circuit protected, please
refer to the Applications Information section covering
SEPIC converters.
The conversion ratio as a function of duty cycle is
=
in continuous conduction mode (CCM).
For a boost converter operating in CCM, the duty cycle
of the main switch can be calculated based on the output
voltage (V OUT ) and the input voltage (V IN ). The maximum
duty cycle (D MAX ) occurs when the converter has the
minimum input voltage:
V OUT ? V IN(MIN)
V OUT
LT3757
GATE
R FLT
M1
Discontinuous conduction mode (DCM) provides higher
conversion ratios at a given frequency at the cost of reduced
efficiencies and higher switching currents.
SENSE
GND
C FLT
R SENSE
3757 F05
Figure 5. The RC Filter on SENSE Pin
3757afd
14
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3757IDD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Boost, Flyback, SEPIC and Inverting Controller |
| LT3757IMSE | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Flyback Controller 2.9V to 40V Input 10-Pin MSOP EP 制造商:Linear Technology 功能描述:CONTROLLER |
| LT3757IMSE#PBF | 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) |
| LT3757IMSE#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) |
| LT3757IMSEPBF | 制造商:Linear Technology 功能描述:Boost Flyback SEPIC Controller MSOP10EP |
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