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参数资料
| 型号： | LT3748EMS#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, PDSO12 |
| 封装： | LEAD FREE, PLASTIC, MSOP-16/12 |
| 文件页数： | 15/30页 |
| 文件大小： | 284K |
| 代理商： | LT3748EMS#TRPBF |
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LT3748
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6. Select the Feedback Resistor for Proper Output
Voltage
Using the iterative process laid out earlier in the Applications
Information section, select the feedback resistor RFB and
program the output voltage to 5V. Adjust the RTC resistor
for temperature compensation of the output voltage. RREF
is selected as 6.04k.
7. Select the Output Capacitor
The output capacitor should be chosen to minimize the
output voltage ripple while considering the increase in
size and cost of a larger capacitor. The following equation
calculates the output voltage ripple:
ΔVMAX =
LPRI ILIM2
2 COUT VOUT
8. Add Snubber Circuitry as Necessary
With the primary components selected, the application
should be constructed to evaluate ringing at the drain of the
MOSFET switch and to evaluate step response to optimize
the compensation network. If using an RC snubber, the
equations from the Applications Information section can
be used or a rough estimate of component values may
come from using the published leakage inductance of the
transformer and selecting a snubber capacitor ranging
from 1 to 3 times larger than the published MOSFET output
capacitance. In this application, the peak MOSFET drain
voltage was measured at maximum load from minimum
VIN and exceeded the 150V rating of the Si7738. A DZ
APPLICATIONS INFORMATION
clamp was considered in order to maximize efficiency but
was unable to turn on fast enough to sufficiently clamp the
very fast leakage spike. The final solution is an RC snubber,
implemented iteratively, that decreases efficiency by less
than 1% across the majority of the output load range while
reducing the worst-case drain voltage spike to just 80V.
Similarly, the anode of the output diode is probed to look
at potential ringing when the MOSFET switch turns on and
a peak of 45V is measured across the diode. Therefore,
no snubber circuitry is required.
9. Optimize the Compensation Network
To set the compensation, the application is first configured
with a 22nF capacitor and 10k resistor as a starting point. A
load step is applied at both light and heavy loads at the 60V
maximum input voltage and the capacitance is decreased
until damping decreases to the desired limit, in this case
with a compensation capacitance of 2.2nF and a response
implying about 60 of phase margin. After verifying stability
at the minimum input voltage, as well, the compensation
capacitance is doubled for safety margin. The series resis-
tance is varied from 5k to 50k but the optimal response is
observed with 24.7k. For best ripple performance, select
a compensation capacitor not less than 1nF, and select a
compensation resistor not greater than 50k.
10. Soft-Start Capacitor and UVLO Resistor Divider
A soft-start capacitor helps during the start-up of the
flyback converter. Select the UVLO resistor divider for
the intended input operation range. These equations are
aforementioned.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3748HMS#PBF | 功能描述:IC REG CTRLR FLYBK ISO CM 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LT3748HMS#TRPBF | 功能描述:IC REG CTRLR FLYBK ISO CM 16MSOP 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 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:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT3748HMSPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:100V Isolated Flyback Controller |
| LT3748HMSTRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:100V Isolated Flyback Controller |
| LT3748IMS#PBF | 功能描述:IC REG CTRLR FLYBK ISO CM 16MSOP 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) |
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