参数资料
型号: LT3825EFE#TRPBF
厂商: Linear Technology
文件页数: 12/32页
文件大小: 0K
描述: IC REG CTRLR FLYBK ISO 16-TSSOP
标准包装: 2,500
PWM 型: 电流模式
输出数: 1
频率 - 最大: 250kHz
占空比: 88%
电源电压: 11 V ~ 18 V
降压:
升压:
回扫:
反相:
倍增器:
除法器:
Cuk:
隔离:
工作温度: -40°C ~ 125°C
封装/外壳: 16-TSSOP(0.173",4.40mm)裸露焊盘
包装: 带卷 (TR)
LT3825
OPERATION
V FLBK
T1
Average primary-side current is expressed in terms of
output current as follows:
V OUT
R1
R2
FB
8
LOAD
COMP I
Q3
Q1 Q2
A1
V FB
+
R CMPF
50k
V IN
SENSE +
12
?
?
MP
?
I IN = K1 ? I OUT
where :
K1 =
V IN ? Eff
So the effective change in V OUT target is:
14 R CMP
13 C CMP
R SENSE
? V OUT = K1 ? ? I OUT ?
thus :
R SENSE
R CMP
? R1 ? N SF
= K1 ? SENSE ? R1 ? N SF
Figure1.LoadCompensationDiagram
3825 F01
? V OUT
? I OUT
R
R CMP
where:
? R1 ? N SF =
R SENSE ESR + R DS(ON)
R SENSE ? ( 1 – DC )
ESR + R DS(ON)
node.Thiseffectivelyincreasesthevoltagerequiredatthe
top of the R1/R2 feedback divider to achieve equilibrium.
The average primary-side switch current increases to main-
tain output voltage regulation as output loading increases.
The increase in average current increases the R CMP resistor
current which affects a corresponding increase in sensed
output voltage, compensating for the IR drops.
Assuming a relatively fixed power supply efficiency, Eff,
power balance gives:
P OUT = Eff ? P IN
V OUT ? I OUT = Eff ? V IN ? I IN
K1 = dimensionless variable related to V IN , V OUT and
efficiency as explained above
R SENSE = external sense resistor
Nominal output impedance cancellation is obtained by
equating this expression with R S(OUT) :
K1 ?
R CMP 1 – DC
Solving for RCMP gives:
R CMP = K1 ? ? R1 ? N SF
The practical aspects of applying this equation to determine
an appropriate value for the R CMP resistor are found in the
Applications Information.
3525fe
12
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LT3837EFE#PBF 功能描述:IC REG CTRLR FLYBK ISO 16-TSSOP 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