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参数资料
| 型号： | LTC3811EUHF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 26/48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
This same RC ?lter, with minor modi?cations, can be used
to extract the resistive component of the current sense
signal in the presence of parasitic inductance. For example,
Figure 13 illustrates the voltage waveform across a 1.5m Ω
Panasonic metal strip resistor (ERJ-M1WTJ1M5U). The
waveform is the superposition of a purely resistive compo-
nent and a purely inductive component and was measured
with a single low impedance scope probe through a BNC
connected directly across the sense resistor terminals.
Based on additional measurements of the inductor ripple
current and the on- and off-times of the primary switch,
the value of the parasitic inductance was determined to
be 0.5nH using the equation:
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 using a low impedance con-
nection to extract the magnitude of the ESL step and
use the equation above to determine the proper ?lter
time constant, keeping the two ?lter resistor values equal
and less than about 200 Ω each. Finally, place these ?lter
components close to the IC and run the positive and
negative sense traces parallel to each other all the way
to the sense resistor.
Inductor DCR Sensing
V ESL(STEP) = ESL ? ? L +
t OFF ?
?ΔI
? t ON
Δ I L ?
?
For applications requiring the highest possible ef?ciency,
the LTC3811 is capable of sensing the voltage drop across
the inductor DCR, as shown in Figure 15. The DCR of
If the R?C time constant is chosen to be exactly the same
as the parasitic inductance divided by the sense resistor
(L/R), the resulting waveform looks resistive again, as
shown in Figure 14. For applications using low maximum
10mV/DIV
the inductor represents the small amount of DC winding
resistance of the copper, which can be less than 1m Ω for
today’s low value, high current inductors. If the external
RC 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. 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.
V IN
250ns/DIV
3811 F13
V IN DRV CC
Figure 13. Current Sense Waveform for the Circuit in Figure 33
LTC3811
BOOST
TG
INDUCTOR
SW
SW
L
DCR
V OUT
BG
PGND
SENSE +
R1 = R2
R1
10mV/DIV
SENSE –
R2
C1
R1 ? C1 = L/DCR
SGND
3811 F15
PLACE R1 NEAR
250ns/DIV
3 8 11 F14
Figure 14. Waveform at the SENSE + and SENSE – Pins
FILTER COMPONENTS
SHOULD BE PLACED NEAR
SENSE + , SENSE – PINS
INDUCTOR TO
MINIMIZE SW NODE
NOISE COUPLING
Using RC – L/R Time Constant Cancellation
Figure15: Current Mode Control Using the Inductor DCR
3811f
26
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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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