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| 型号： | LTC3855IFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 17/44页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 38TSSOP |
| 标准包装： | 2,000 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 850kHz |
| 占空比： | 95% |
| 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 ~ 125°C |
| 封装/外壳： | 38-TFSOP （0.173"，4.40mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3855
APPLICATIONS INFORMATION
V IN
INTV CC
V IN
V IN
INTV CC
V IN
BOOST
TG
SW
LTC3855
SENSE RESISTOR
PLUS PARASITIC
INDUCTANCE
R S ESL
V OUT
OPTIONAL
TEMP COMP
NETWORK
BOOST
TG
SW
LTC3855
INDUCTOR
L DCR
V OUT
BG
PGND
SENSE +
SENSE –
SGND
C F
R F
R F
C F ? 2 RF ≤ ESL/R S
POLE-ZERO
CANCELLATION
R NTC
R S
R P
ITEMP
SGND
BG
PGND
SENSE +
SENSE –
C1*
R2
R1**
3855 F02a
FILTER COMPONENTS
PLACED NEAR SENSE PINS
**PLACE R1 NEXT TO *PLACE C1 NEAR SENSE + , R1||R2 × C1 =
INDUCTOR SENSE – PINS
L
DCR
R SENSE(EQ) = DCR
R2
R1 + R2
3855 F02b
(2a) Using a Resistor to Sense Current
(2b) Using the Inductor DCR to Sense Current
Figure 2. Two Different Methods of Sensing Current
500ns/DIV
500ns/DIV
the resulting waveform looks resistive again, as shown
in Figure 4. For applications using low maximum sense
voltages, check the sense resistor manufacturer’s data
sheet for information about parasitic inductance. In the
absence of data, measure the voltage drop directly across
the sense resistor to extract the magnitude of the ESL
step and use the equation above to determine the ESL.
However, do not over-filter. Keep the RC time constant less
than or equal to the inductor time constant to maintain a
high enough ripple voltage on V RSENSE .
V ESL(STEP)
V SENSE
20mV/DIV
3855 F03
Figure 3. Voltage Waveform Measured
Directly Across the Sense Resistor.
V SENSE
20mV/DIV
3855 F04
Figure 4. Voltage Waveform Measured After the
Sense Resistor Filter. C F = 1000pF, R F = 100?.
The above generally applies to high density/high current
applications where I (MAX) >10A and low values of induc-
tors are used. For applications where I (MAX) <10A, set R F
to 10 Ohms and C F to 1000pF. This will provide a good
starting point.
The filter components need to be placed close to the IC.
The positive and negative sense traces need to be routed
as a differential pair and Kelvin connected to the sense
resistor.
Inductor DCR Sensing
For applications requiring the highest possible efficiency at
high load currents, the LTC3855 is capable of sensing the
voltage drop across the inductor DCR, as shown in Figure
2b. The DCR of the inductor represents the small amount
of DC winding resistance of the copper, which can be less
than 1m? for today’s low value, high current inductors.
In a high current application requiring such an inductor,
conduction loss through a sense resistor would cost sev-
eral points of efficiency compared to DCR sensing.
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 drop across
the inductor DCR multiplied by R2/(R1 + R2). R2 scales the
voltage across the sense terminals for applications where
the DCR is greater than the target sense resistor value.
To properly dimension the external filter components, the
DCR of the inductor must be known. It can be measured
using a good RLC meter, but the DCR tolerance is not
3855f
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相关代理商/技术参数 |
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| LTC3855IUJ#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 |
| LTC3855IUJ#PBF-ES | 制造商:Linear Technology 功能描述: |
| LTC3855IUJ#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® 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) |
| LTC3856EFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 38TFSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 标准包装:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 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:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
| LTC3856EFE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 38TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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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