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| 型号： | LTC3854EDDB#TRMPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 12-DFN |
| 标准包装： | 500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 440kHz |
| 占空比： | 98% |
| 电源电压： | 4.5 V ~ 38 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 ~ 85°C |
| 封装/外壳： | 12-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3854
APPLICATIONS INFORMATION
R SENSE = 0.8 ?
? I L
I MAX +
TheLTC3854canbeconfiguredtouseeitherDCR(inductor
winding resistance) sensing or low value resistor sensing.
The choice of the two current sensing schemes is largely
a design tradeoff between cost, power consumption, and
accuracy. DCR sensing is becoming popular because it
eliminates expensive current sensing resistors and is
more power efficient, especially in high current applica-
tions. However, current sensing resistors provide the most
accurate current limits for the controller. Other external
component selection is driven by the load requirement,
and begins with the selection of R SENSE (if R SENSE is used)
and inductor value. Next, the power MOSFETs and Schottky
diodes are selected. Finally, input and output capacitors are
selected. The Typical Application shown on the first page
can be configured for operation up to 38V on V IN .
SENSE+ and SENSE– Pins
The SENSE+ and SENSE– pins are the inputs to the cur-
rent comparator. The common mode input voltage range
of the current comparator is 0V to 5.5V. Both SENSE pins
are high impedance inputs with small input bias currents
of less than 1μA. When the SENSE pins ramp up from 0V
to 1.4V, small bias currents flow out of the SENSE pins.
When the SENSE pins ramp down from 5.5V to 1.1V, the
small bias currents flow into the SENSE pins. The high
impedance inputs to the current comparator allow accurate
DCR sensing.
V IN
INTV CC
BOOST
Using a Sense Resistor for Current Sensing
A typical sensing circuit using a discrete resistor is shown
in Figure 1. R SENSE is chosen based on the required output
current.
The current comparator has a maximum threshold of 50mV.
The input common mode range of the current comparator
is 0V to 5.5V. The current comparator threshold sets the
peak of the inductor current, yielding a maximum aver-
age output current I MAX equal to the peak value less half
the peak-to-peak ripple current, ? I L . Allowing a margin
of 20% for variations in the IC and external component
values yields:
V SENSE(MAX)
2
Inductor DCR Sensing
For applications requiring the highest possible efficiency,
the LTC3854 is capable of sensing the voltage drop across
the inductor DCR, as shown in Figure 2. The DCR of the
inductor represents the small amount of DC copper wind-
ing resistance, which can be less than 1m? for today’s
low value, high current inductors. When the external
R1||R2 ?C1 time constant is chosen to be equal to the
L/DCR time constant, the voltage drop across the external
LTC3854
TG
SW
R SENSE
V OUT
BG
GND
SENSE +
SENSE –
FILTER COMPONENTS
PLACED NEAR SENSE PINS
3854 F01
Figure 1. Using a Resistor to Sense Current with the LTC3854
3854fb
10
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3854EMSE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 12-MSOP 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 |
| LTC3854EMSE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 12-MSOP 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) |
| LTC3854IDDB#PBF | 制造商:Linear Technology 功能描述:DP-SWREG/Controller, Cut Tape Small Footprint, Low Pin Count Synchronous Step-Do |
| LTC3854IDDB#TRMPBF | 功能描述:IC REG CTRLR BUCK PWM CM 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) |
| LTC3854IDDB#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 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) |
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