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参数资料
| 型号： | LTC1871EMS |
| 厂商： | Linear Technology |
| 文件页数： | 9/36页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST FLYBK CM 10MSOP |
| 标准包装： | 50 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 占空比： | 97% |
| 电源电压： | 2.5 V ~ 36 V |
| 降压： | 无 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 包装： | 管件 |
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LTC1871
OPERATION
V IN
L
D
V OUT
reset pulse to the main RS latch. Because this RS latch is
reset-dominant, the power MOSFET is actively held off for
V IN
SENSE
+
C OUT
the duration of an output overvoltage condition.
V SW
GATE
GND
GND
2a. SENSE Pin Connection for
Maximum Ef?ciency (V SW < 36V)
The LTC1871 can be used either by sensing the voltage
drop across the power MOSFET or by connecting the
SENSE pin to a conventional shunt resistor in the source
of the power MOSFET, as shown in Figure 2. Sensing the
voltage across the power MOSFET maximizes converter
ef?ciency and minimizes the component count, but limits
V IN
V IN
GATE
L
D
V SW
V OUT
the output voltage to the maximum rating for this pin (36V).
By connecting the SENSE pin to a resistor in the source
of the power MOSFET, the user is able to program output
voltages signi?cantly greater than 36V.
+
GND
SENSE
GND
R S
C OUT
1871 F02
Programming the Operating Mode
For applications where maximizing the ef?ciency at very
2b. SENSE Pin Connection for Precise
Control of Peak Current or for V SW > 36V
Figure 2. Using the SENSE Pin On the LTC1871
The nominal operating frequency of the LTC1871 is pro-
grammed using a resistor from the FREQ pin to ground
and can be controlled over a 50kHz to 1000kHz range. In
addition, the internal oscillator can be synchronized to
an external clock applied to the MODE/SYNC pin and can
be locked to a frequency between 100% and 130% of its
nominal value. When the MODE/SYNC pin is left open, it
is pulled low by an internal 50k resistor and Burst Mode
operation is enabled. If this pin is taken above 2V or an
external clock is applied, Burst Mode operation is disabled
and the IC operates in continuous mode. With no load (or
an extremely light load), the controller will skip pulses in
order to maintain regulation and prevent excessive output
ripple.
The RUN pin controls whether the IC is enabled or is in a low
current shutdown state. A micropower 1.248V reference
and comparator C2 allow the user to program the supply
voltage at which the IC turns on and off (comparator C2
has 100mV of hysteresis for noise immunity). With the
RUN pin below 1.248V, the chip is off and the input supply
current is typically only 10μA.
An overvoltage comparator OV senses when the FB pin
exceeds the reference voltage by 6.5% and provides a
light loads (e.g., <100μA) is a high priority, the current
in the output divider could be decreased to a few micro-
amps and Burst Mode operation should be applied (i.e.,
the MODE/SYNC pin should be connected to ground).
In applications where ?xed frequency operation is more
critical than low current ef?ciency, or where the lowest
output ripple is desired, pulse-skip mode operation should
be used and the MODE/SYNC pin should be connected
to the INTV CC pin. This allows discontinuous conduction
mode (DCM) operation down to near the limit de?ned
by the chip’s minimum on-time (about 175ns). Below
this output current level, the converter will begin to skip
cycles in order to maintain output regulation. Figures 3
and 4 show the light load switching waveforms for Burst
Mode and pulse-skip mode operation for the converter
in Figure 1.
Burst Mode Operation
Burst Mode operation is selected by leaving the MODE/
SYNC pin unconnected or by connecting it to ground. In
normal operation, the range on the I TH pin corresponding to
no load to full load is 0.30V to 1.2V. In Burst Mode opera-
tion, if the error ampli?er EA drives the I TH voltage below
0.525V, the buffered I TH input to the current comparator
C1 will be clamped at 0.525V (which corresponds to 25%
of maximum load current). The inductor current peak is
then held at approximately 30mV divided by the power
1871fe
9
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1871EMS#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:- 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 |
| LTC1871EMS#TR | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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) |
| LTC1871EMS#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: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) |
| LTC1871EMS-1#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: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) |
| LTC1871EMS-1#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: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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