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参数资料
| 型号： | LTC3805IMSE-5#TRMPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 700 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封装： | LEAD FREE, PLASTIC, MSOP-10 |
| 文件页数： | 5/20页 |
| 文件大小： | 203K |
| 代理商： | LTC3805IMSE-5#TRMPBF |
LTC3805-5
13
38055fb
Figure 3. Setting RUN Pin Voltage and Run/Stop Control
APPLICATIONS INFORMATION
External Run/Stop Control
To implement external run control, place a small N-channel
MOSFET from the RUN pin to GND as shown in Figure 3.
Drive the gate of this MOSFET high to pull the RUN pin to
ground and prevent converter operation.
Selecting Feedback Resistor Divider Values
The regulated output voltage is determined by the resistor
divider across VOUT (R3 and R4 in Figure 8). The ratio
of R4 to R3 needed to produce a desired VOUT can be
calculated:
R
VV
V
R
OUT
3
08
4
=
.
.
Choose resistance values for R3 and R4 to be as large as
possible in order to minimize any efciency loss due to the
static current drawn from VOUT, but just small enough so
that when VOUT is in regulation the input current to the VFB
pin is less than 1% of the current through R3 and R4. A
good rule of thumb is to choose R4 to be less than 80k.
Feedback in Isolated Applications
Isolated applications do not use the FB pin and error ampli-
er but control the ITH pin directly using an optoisolator
driven on the other side of the isolation barrier as shown
in Figure 4. For isolated converters, the FB pin is grounded
which provides pull-up on the ITH pin. This pull-up is not
enough to properly bias the optoisolator which is typically
biased using a resistor to VCC. Since the ITH pin cannot
sink the optoisolator bias current, a diode is required to
block it from the ITH pin. A Schottky diode should be used
to ensure that the optoisolator is able to pull ITH down to
its lower clamp.
Oscillator Synchronization
The oscillator may be synchronized to an external clock
by connecting the synchronization signal to the SYNC pin.
The LTC3805-5 oscillator and turn-on of the switch are
synchronized to the rising edge of the external clock. The
frequency of the external sync signal must be ±33% with
respect to fOSC (as programmed by RFS). Additionally, the
value of fSYNC must be between 70kHz and 700kHz.
Current Sense Resistor Considerations
The external current sense resistor (RSENSE in Figure 8)
allows the user to optimize the current limit behavior for
the particular application. As the current sense resistor
is varied from several ohms down to tens of milliohms,
peak switch current goes from a fraction of an ampere
to several amperes. Care must be taken to ensure proper
circuit operation, especially with small current sense
resistor values.
LTC3805-5
RUN
RUN/STOP
CONTROL
(OPTIONAL)
R1
R2
GND
38055 F03
VIN
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相关代理商/技术参数 |
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| LTC3805MPMSE#PBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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 |
| LTC3805MPMSE#TRPBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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 |
| LTC3805MPMSE-5#PBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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 |
| LTC3805MPMSE-5#TRPBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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 |
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