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参数资料
| 型号： | LTC3872IDDB#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 7/22页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 8-DFN |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 650kHz |
| 电源电压： | 2.75 V ~ 9.8 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： | 8-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
LTC3872
OPERATION
Main Control Loop
The LTC3872 is a No R SENSE constant frequency, current
mode controller for DC/DC boost, SEPIC and flyback
converter applications. The LTC3872 is distinguished from
conventional current mode controllers because the current
control loop can be closed by sensing the voltage drop
across the power MOSFET switch or across a discrete
sense resistor, as shown in Figures 1 and 2. This No?R SENSE
sensing technique improves efficiency, increases power
density and reduces the cost of the overall solution.
For circuit operation, please refer to the Block Diagram
of the IC and the Typical Application on the front page. In
normal operation, the power MOSFET is turned on when
the oscillator sets the RS latch and is turned off when the
current comparator resets the latch. The divided-down
output voltage is compared to an internal 1.2V reference by
the error amplifier, which outputs an error signal at the I TH
pin. The voltage on the I TH pin sets the current comparator
input threshold. When the load current increases, a fall in
the FB voltage relative to the reference voltage causes the
I TH pin to rise, which causes the current comparator to
trip at a higher peak inductor current value. The average
inductor current will therefore rise until it equals the load
current, thereby maintaining output regulation.
The LTC3872 can be used either by sensing the voltage
drop across the power MOSFET or by connecting the SW
pin to a conventional sensing resistor in the source of the
power MOSFET. Sensing the voltage across the power
MOSFET maximizes converter efficiency and minimizes the
component count; the maximum rating for this pin, 60V,
allows MOSFET sensing in a wide output voltage range.
The RUN/SS pin controls whether the IC is enabled or is
in a low current shutdown state. With the RUN/SS pin
below 0.85V, the chip is off and the input supply current is
typically only 8μA. With an external capacitor connected to
the RUN/SS pin an optional external soft-start is enabled.
A 0.7μA trickle current will charge the capacitor, pulling
the RUN/SS pin above shutdown threshold and slowly
ramping RUN/SS to limit the V ITH during start-up. Because
the noise on the SW pin could couple into the RUN/SS
pin, disrupting the trickle charge current that charges the
RUN/SS pin, a 1M resistor is recommended to pull-up
the RUN/SS pin when external soft-start is used. When
RUN/SS is driven by an external logic, a minimum of 2.75V
logic is recommended to allow the maximum I TH range.
Light Load Operation
Under very light load current conditions, the I TH pin volt-
age will be very close to the zero current level of 0.85V.
As the load current decreases further, an internal offset at
the current comparator input will assure that the current
comparator remains tripped (even at zero load current) and
the regulator will start to skip cycles, as it must, in order
to maintain regulation. This behavior allows the regulator
to maintain constant frequency down to very light loads,
resulting in low output ripple as well as low audible noise
and reduced RF interference, while providing high light
load efficiency.
V IN
L
D
V OUT
V IN
L
D
V OUT
V IN
SW
LTC3872
V SW
+
C OUT
V IN
NGATE
LTC3872
V SW
+
C OUT
NGATE
SW
GND
GND
R SENSE
GND
3872 F01
Figure 1. SW Pin (Internal Sense Pin)
Connection for Maximum Efficiency
GND
3872 F02
Figure 2. SW Pin (Internal Sense Pin)
Connection for Sensing Resistor
3872fc
For more information www.linear.com/LTC3872
7
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3872ITS8#PBF | 制造商:Linear Technology 功能描述:DP-SWREG/Controller, CUT TAPE No Rsense, Current Mode Boost DC/DC Controller |
| LTC3872ITS8#TRMPBF | 功能描述:IC REG CTRLR BST PWM CM TSOT23-8 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) |
| LTC3872ITS8#TRPBF | 功能描述:IC REG CTRLR BST PWM CM TSOT23-8 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) |
| LTC3873EDDB#PBF | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Up 8.8V to 75V Input 8-Pin DFN EP |
| LTC3873EDDB#TRM | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Up 8.8V to 75V Input T/R |
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