- 您现在的位置：买卖IC网 > PDF目录15304 > LT3825EFE#TRPBF (Linear Technology)IC REG CTRLR FLYBK ISO 16-TSSOP PDF资料下载
参数资料
| 型号： | LT3825EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/32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： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 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) |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页当前第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页
LT3825
APPLICATIONS INFORMATION
Setting Feedback Resistive Divider
The expression for V OUT developed in the Operation sec-
tion is rearranged to yield the following expression for the
feedback resistors:
above nominal so I PK = 3.64A . If there is a 10% tolerance
on R SENSE and minimum V SENSE = 80mV, then R SENSE ?
110% = 80mV/3.64A and nominal R SENSE = 20mΩ. Round
to the nearest available lower value.
? ? V
?
– 1 ?
?
R1 = R2
? ? OUT
?
+ I SEC ? ( ESR + R DS(ON) ) ??
V FB ? N SF
?
?
Selecting the Load Compensation Resistor
The expression for R CMP was derived in the Operation
section as:
Continuing the example, if ESR + R DS(ON) = 8mΩ, R2 =
3.32k, then:
R CMP = K1 ?
R SENSE ? ( 1 – DC )
ESR + R DS(ON)
? R1 ? N SF = R S(OUT)
– 1 ? = 37.6k
R1 = 3.4k ?
? V OUT ? 5
20m ? ? ( 1 – 0.455 )
R CMP = 0.116 ?
? 5 + 8 ? 0.008 ?
? 1.232 ? 1/ 3 ?
choose 37.4k.
It is recommended that the Thevenin impedance of the
resistive divider (R1||R2) is roughly 3k for bias current
cancellation and other reasons.
Current Sense Resistor Considerations
Continuing the example:
K1 = ? ?= = 0.116
? V IN ? Eff ? 48 ? 90%
If ESR + R DS(ON) = 8m ?
= 1.96k
8m ?
? 37.4k ?
The external current sense resistor is used to control peak
primary switch current, which controls a number of key
converter characteristics including maximum power and
external component ratings. Use a noninductive current
sense resistor (no wire-wound resistors). Mounting the
resistor directly above an unbroken ground plane con-
nected with wide and short traces keeps stray resistance
and inductance low.
The dual sense pins allow for a fully Kelvined connection.
Make sure that SENSE + and SENSE – are isolated and con-
nect close to the sense resistor to preserve this.
Peak current occurs at 98mV of sense voltage V SENSE . So
the nominal sense resistor is V SENSE /I PK . For example, a
peak switch current of 10A requires a nominal sense resistor
of 0.010Ω. Note that the instantaneous peak power in the
sense resistor is 1W, and that it is rated accordingly. The
use of parallel resistors can help achieve low resistance,
low parasitic inductance and increased power capability.
Size R SENSE using worst-case conditions, minimum L P ,
V SENSE and maximum V IN . Continuing the example, let us
assume that our worst-case conditions yield an I PK 40%
This value for R CMP is a good starting point, but empiri-
cal methods are required for producing the best results.
This is because several of the required input variables are
difficult to estimate precisely. For instance, the ESR term
above includes that of the transformer secondary, but its
effective ESR value depends on high frequency behavior,
not simply DC winding resistance. Similarly, K1 appears
as a simple ratio of V IN to V OUT times (differential) ef-
ficiency, but theoretically estimating efficiency is not a
simple calculation.
The suggested empirical method is as follows:
1. Build a prototype of the desired supply including the
actual secondary components.
2. Temporarily ground the C CMP pin to disable the load
compensation function. Measure output voltage while
sweeping output current over the expected range.
Approximate the voltage variation as a straight line,
?V OUT /?I OUT = R S(OUT) .
3. Calculate a value for the K1 constant based on V IN , V OUT
and the measured efficiency.
3525fe
16
相关PDF资料 |
PDF描述 |
|---|---|
| VE-J2X-EY-F2 | CONVERTER MOD DC/DC 5.2V 50W |
| IMC1210EBR10J | INDUCTOR WW 100NH 5% 1210 |
| PCF1D820MCL1GS | CAP ALUM 82UF 20V 20% SMD |
| AS1902-C23-T | IC SUPERVISOR ACT HIGH SOT23-3 |
| LT3837EFE#TRPBF | IC REG CTRLR FLYBK ISO 16-TSSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT382B | 制造商:EDSYN 功能描述:TIP CONICAL 0.5X15.8MM |
| LT383 | 制造商:EDSYN 功能描述: |
| LT3837 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Low VIN, 8A DC/DC μModule Regulator |
| LT3837EFE | 制造商:Linear Technology 功能描述:Current Mode PWM Controller 16-Pin TSSOP EP |
| 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 |
发布紧急采购，3分钟左右您将得到回复。