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| 型号： | LTC3811EUHF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 25/48页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 38-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 850kHz |
| 占空比： | 90% |
| 电源电压： | 4.5 V ~ 30 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： | 38-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3811
APPLICATIONS INFORMATION
pin. For applications requiring maximum current limit ac-
curacy, a higher peak sense voltage (e.g., 85mV) should
be chosen. An additional bene?t of a higher peak SENSE
pin threshold is a slight reduction in the minimum on-
time of the controller. That is, for a given ripple current
in the inductor, a higher peak sense voltage results in
higher SENSE pin dV/dt, speeding up the input stage of
the current comparator slightly. For applications where
high ef?ciency and tight current limit accuracy are both
important, the peak current sense voltage can be reduced
to as low as 24mV.
In multiphase applications, only one error ampli?er is used
to control all of the phase current comparators. As a result,
in multiphase applications all of the RNG pins should all be
tied to the same potential, in order to program the same
power stage g m for each phase.
SENSE + and SENSE – Pins
The common mode input voltage range of the current
comparators is 0V to 3.5V. Continuous linear operation is
with operation up to 1MHz are becoming more common.
Under these conditions the voltage drop across the sense
resistor’s parasitic inductance is no longer negligible.
A typical sensing circuit using a discrete resistor is shown
in Figure 12. In previous generations of controllers, a small
RC ?lter placed near the IC was commonly used to reduce
the effects of capacitive and inductive noise coupled in
the sense traces on the PCB. A typical ?lter consists of
two series 10 Ω resistors connected to a parallel 1000pF
capacitor, resulting in a time constant of 20ns.
2.5
2.0
1.5
1.0
0.5
provided throughout this range, allowing output voltages
between 0.6V (the reference input to the error ampli?ers)
and 3.3V. The SENSE + and SENSE – pins are also the inputs
0
0
0.5
1.0 1.5 2.0 2.5 3.0 3.5 4.0
COMMON MODE VOLTAGE (V)
3811 G33
to the voltage positioning current sense g m ampli?er.
Under normal operation, a small current of about 1.5μA
?ows out of the SENSE inputs and represents the total
base current of the two vertical PNP input stages (one in
Figure 11. SENSE Pin Input Bias Current vs
Common Mode (Output) Voltage
the current comparator and one in the voltage positioning
current sense ampli?er). When the common mode voltage
V IN
DRV CC
V IN
is lower than about 0.4V, the current ?owing out of the
SENSE pins increases, up to about 2.2μA at V SENSE = 0V.
Figure 11 illustrates the change in the SENSE pin current
as a function of common mode voltage.
LTC3811
BOOST
TG
SW
SENSE RESISTOR
PLUS PARASITIC
INDUCTANCE
R S ESL
V OUT
Sensing Techniques Using Low Value Resistors
For previous generation current mode controllers, the
maximum sense voltage was high enough (e.g., 75mV
for the LTC1628 family) that the voltage drop across the
BG
PGND
SENSE +
SENSE –
SGND
C F
R F
R F
C F ? 2R F = ESL/R S
POLE-ZERO
CANCELLATION
parasitic inductance of the sense resistor represented a
relatively small error. For today’s highest current density
solutions, however, the value of the sense resistor can be
FILTER COMPONENTS
PLACED NEAR SENSE PINS
3811 F12
less than 1m Ω and the peak sense voltage can be as low as
Figure 12. Using a Resistor to Sense Current with the LTC3811
24mV. In addition, inductor ripple currents greater than 50%
3811f
25
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相关代理商/技术参数 |
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| LTC3812EFE5#PBF | 制造商:Linear Technology 功能描述: |
| LTC3812EFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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 |
| LTC3812EFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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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