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参数资料
| 型号： | LTC3805MPMSE#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封装： | LEAD FREE, PLASTIC, MSOP-10 |
| 文件页数： | 19/20页 |
| 文件大小： | 248K |
| 代理商： | LTC3805MPMSE#TRPBF |
LTC3805
8
3805ff
OPERATION
The LTC3805 is a programmable-frequency current mode
controller for flyback, boost and SEPIC DC/DC converters.
The LTC3805 is designed so that none of its pins need to
come in contact with the input or output voltages of the
power supply circuit of which it is a part, allowing the
conversionofvoltageswellbeyondtheLTC3805’sabsolute
maximum ratings.
Main Control Loop
Please refer to the Block Diagram of this data sheet and
the Typical Application shown on the front page. An ex-
ternal resistive voltage divider presents a fraction of the
output voltage to the FB pin. The divider is designed so
that when the output is at the desired voltage, the FB pin
voltage equals the 800mV internal reference voltage. If
the load current increases, the output voltage decreases
slightly, causing the FB pin voltage to fall below the 800mV
reference. The error amplifier responds by feeding current
into the ITH pin causing its voltage to rise. Conversely, if
the load current decreases, the FB voltage rises above the
800mVreferenceandtheerroramplifiersinkscurrentaway
from the ITH pin causing its voltage to fall.
ThevoltageattheITHpincontrolsthepulse-widthmodula-
tor formed by the oscillator, current comparator and SR
latch. Specifically, the voltage at the ITH pin sets the cur-
rentcomparator’stripthreshold.Thecurrentcomparator’s
ISENSEinputmonitorsthevoltageacrossanexternalcurrent
sense resistor in series with the source of the external
MOSFET. At the start of a cycle, the LTC3805’s oscillator
sets the SR latch and turns on the external power MOSFET.
The current through the external power MOSFET rises as
does the voltage on the ISENSE pin. The LTC3805’s current
comparator trips when the voltage on the ISENSE pin ex-
ceeds a voltage proportional to the voltage on the ITH pin.
This resets the SR latch and turns off the external power
MOSFET. In this way, the peak current levels through the
external MOSFET and the flyback transformer’s primary
and secondary windings are controlled by the voltage on
the ITH pin. If the current comparator does not trip, the
LTC3805 automatically limits the duty cycle to 80%, resets
the SR latch, and turns off the external MOSFET.
The path from the FB pin, through the error amplifier,
current comparator and the SR latch implements the
closed-loop current mode control required to regulate the
output voltage against changes in input voltage or output
current. For example, if the load current increases, the
output voltage decreases slightly, and sensing this, the
error amplifier sources current from the ITH pin, raising
thecurrentcomparatorthreshold,thusincreasingthepeak
currents through the transformer primary and secondary.
This delivers more current to the load and restores the
output voltage to the desired level.
TheITHpinservesasthecompensationpointforthecontrol
loop. Typically, an external series RC network is connected
from ITH to ground and is chosen for optimal response to
load and line transients. The impedance of this RC network
converts the output current of the error amplifier to the
ITH voltage which sets the current comparator threshold
and commands considerable influence over the dynamics
of the voltage regulation loop.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3806EDE | 功能描述:IC REG CTRLR FLYBACK PWM 12-DFN RoHS:否 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) |
| LTC3806EDE#PBF | 功能描述:IC REG CTRLR FLYBACK PWM 12-DFN 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) |
| LTC3806EDE#TR | 功能描述:IC REG CTRLR FLYBACK PWM 12-DFN RoHS:否 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) |
| LTC3806EDE#TRPBF | 功能描述:IC REG CTRLR FLYBACK PWM 12-DFN 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) |
| LTC3808EDE | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Sync Step Down 2.75V to 9.8V Input 14-Pin DFN EP |
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