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| 型号： | LTC3852EUDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR DOUBLER PWM 24-QFN |
| 标准包装： | 73 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 810kHz |
| 占空比： | 99% |
| 电源电压： | 2.7 V ~ 38 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 是 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 24-WFQFN 裸露焊盘 |
| 包装： | 管件 |
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LTC3852
APPLICATIONS INFORMATION
R SENSE = 0. 8 ?
TheTypicalApplicationonthe?rstpageofthisdatasheet
is a basic LTC3852 application circuit. The LTC3852 can
be con?gured to use either DCR (inductor resistance)
sensing or low value resistor sensing. The choice of the
two current sensing schemes is largely a design trade-off
between cost, power consumption and accuracy. DCR
sensing is popular because it saves expensive current
half the peak-to-peak ripple current, D I L . Allowing a margin
of 20% for variations in the IC and external component
values yields:
V MAX
I MAX + Δ I L /2
sensing resistors and is more power ef?cient, especially
in high current applications. However, current sensing
resistors provide the most accurate current limits for the
controller. Other external component selection is driven
V IN2
INTV CC
BOOST
TG
V IN
by the load requirement, and begins with the selection of
R SENSE (if R SENSE is used) and the inductor value. Next,
the power MOSFETs and Schottky diodes are selected.
Finally, input and output capacitors are selected.
SW
LTC3852
BG
GND2
R SENSE
V OUT
SENSE +
FILTER COMPONENTS
SENSE + and SENSE – Pins
The SENSE + and SENSE – pins are the inputs to the current
comparators. The common mode input voltage range of
the current comparators is 0V to 5.5V. Both SENSE pins
are high impedance inputs with small base currents of
less than 1μA. When the SENSE pins ramp up from 0V
to 1.4V, the small base currents ?ow out of the SENSE
pins. When the SENSE pins ramp down from 5V to 1.1V,
the small base currents ?ow into the SENSE pins. The
high impedance inputs to the current comparators allow
accurate DCR sensing. However, care must be taken not
to ?oat these pins during normal operation.
Low Value Resistors Current Sensing
A typical sensing circuit using a discrete resistor is shown
in Figure 2. R SENSE is chosen based on the required
output current. For simplicity, the charge pump section
is omitted.
The current comparator has a maximum threshold,
V MAX = 50mV. The current comparator threshold sets the
maximum peak of the inductor current, yielding a maximum
average output current, I MAX , equal to the peak value less
SENSE –
3852 F02
PLACED NEAR SENSE PINS
Figure 2. Using a Resistor to Sense Current with the LTC3852
Inductor DCR Sensing
For applications requiring the highest possible ef?ciency,
the LTC3852 is capable of sensing the voltage drop across
the inductor DCR, as shown in Figure 3. The DCR of the
inductor represents the small amount of DC winding
resistance of the copper, which can be less than 1m W for
today’s low value, high current inductors. If the external
R1||R2 ? C1 time constant is chosen to be exactly equal
to the L/DCR time constant, the voltage drop across the
external capacitor is equal to the voltage drop across the
inductor DCR multiplied by R2/(R1 + R2). Therefore, R2
may be used to scale the voltage across the sense terminals
when the DCR is greater than the target sense resistance.
Check the manufacturer’s data sheet for speci?cations
regarding the inductor DCR, in order to properly dimension
the external ?lter components. The DCR of the inductor
can also be measured using a good RLC meter.
3852f
15
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| LTC3852IUDD#PBF | 功能描述:IC REG CTRLR DOUBLER PWM 24-QFN 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) |
| LTC3852IUDD#TRPBF | 功能描述:IC REG CTRLR DOUBLER PWM 24-QFN 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) |
| LTC3853EUJ#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 40-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC3853EUJ#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 40-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC3853EUJPBF | 制造商:Linear Technology 功能描述:DC-DC Controller Triple Buck 24V QFN40 |
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