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| 型号： | LT3511HMS#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 0.43 A SWITCHING REGULATOR, 650 kHz SWITCHING FREQ-MAX, PDSO12 |
| 封装： | LEAD FREE, PLASTIC, MSOP-12/16 |
| 文件页数： | 24/26页 |
| 文件大小： | 298K |
| 代理商： | LT3511HMS#TRPBF |
LT3511
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3511fb
operaTion
The LT3511 is a current mode switching regulator IC de-
signed specifically for the isolated flyback topology. The
key problem in isolated topologies is how to communicate
information regarding the output voltage from the isolated
secondary side of the transformer to the primary side.
Historically, opto-isolators or extra transformer windings
communicate this information across the transformer.
Opto-isolator circuits waste output power, and the extra
components increase the cost and physical size of the
power supply. Opto-isolators can also exhibit trouble due
to limited dynamic response, nonlinearity, unit-to-unit
variation and aging over life. Circuits employing an extra
transformer winding also exhibit deficiencies. Using an
extra winding adds to the transformer’s physical size and
cost, and dynamic response is often mediocre.
In the LT3511, the primary-side flyback pulse provides
information about the isolated output voltage. In this man-
ner, neither opto-isolator nor extra transformer winding is
required for regulation. Two resistors program the output
voltage. Since this IC operates in boundary mode, the part
calculates output voltage from the switch pin when the
secondary current is almost zero.
The Block Diagram shows an overall view of the system.
Many of the blocks are similar to those found in traditional
switching regulators including internal bias regulator, os-
cillator, logic, current amplifier, current comparator, driver,
and output switch. The novel sections include a special
flyback error amplifier and a temperature compensation
circuit. In addition, the logic system contains additional
logic for boundary mode operation.
The LT3511 features boundary mode control, where the
part operates at the boundary between continuous con-
duction mode and discontinuous conduction mode. The
VC pin controls the current level just as it does in normal
current mode operation, but instead of turning the switch
on at the start of the oscillator period, the part turns on the
switch when the secondary-side winding current is zero.
Boundary Mode Operation
Boundary mode is a variable frequency, current mode
switching scheme. The switch turns on and the inductor
current increases until a VC pin controlled current limit.
After the switch turns off, the voltage on the SW pin rises
to the output voltage divided by the secondary-to-primary
transformer turns ratio plus the input voltage. When the
secondary current through the diode falls to zero, the SW
pin voltage falls below VIN. A discontinuous conduction
mode (DCM) comparator detects this event and turns the
switch back on.
Boundarymodereturnsthesecondarycurrenttozeroevery
cycle,soparasiticresistivevoltagedropsdonotcauseload
regulation errors. Boundary mode also allows the use of a
smaller transformer compared to continuous conduction
mode and does not exhibit subharmonic oscillation.
At low output currents, the LT3511 delays turning on the
switch, and thus operates in discontinuous mode. Unlike
traditional flyback converters, the switch has to turn on
to update the output voltage information. Below 0.6V on
the VC pin, the current comparator level decreases to
its minimum value, and the internal oscillator frequency
decreases. With the decrease of the internal oscillator,
the part starts to operate in DCM. The output current is
able to decrease while still allowing a minimum switch off
time for the flyback error amplifier. The typical minimum
internal oscillator frequency with VC equal to 0V is 40kHz.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3511IMS#PBF | 功能描述:IC REG FLYBK ISO ADJ .24A 16MSOP 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 |
| LT3511IMS#TRPBF | 功能描述:IC REG FLYBK ISO ADJ .24A 16MSOP 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 |
| LT3511MPMS#PBF | 功能描述:IC REG FLYBK ISO ADJ .24A 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3511MPMS#TRPBF | 功能描述:IC REG FLYBK ISO ADJ .24A 16MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3512 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic High Voltage Isolated Flyback Converter |
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