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參數資料
| 型號： | LT3845AMPFE#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 4.40 MM, LEAD FREE, PLASTIC, TSSOP-16 |
| 文件頁數： | 7/26頁 |
| 文件大?。?/td> | 284K |
| 代理商： | LT3845AMPFE#TRPBF |
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APPLICATIONS INFORMATION
Inductor Selection
The critical parameters for selection of an inductor
are minimum inductance value, volt-second product,
saturation current and/or RMS current.
For a given
DIL, The minimum inductance value is calcu-
lated as follows:
L
≥ VOUT
VIN(MAX) – VOUT
fSW VIN(MAX) DIL
fSW is the switch frequency.
The typical range of values for
DIL is (0.2 IOUT(MAX)) to
(0.5 IOUT(MAX)), where IOUT(MAX) is the maximum load
current of the supply. Using
DIL = 0.3 IOUT(MAX) yields a
good design compromise between inductor performance
versusinductorsizeandcost.Avalueof
DIL=0.3IOUT(MAX)
producesa±15%ofIOUT(MAX)ripplecurrentaroundtheDC
output current of the supply. Lower values of
DIL require
larger and more costly magnetics. Higher values of
DIL
will increase the peak currents, requiring more filtering
on the input and output of the supply. If
DIL is too high,
the slope compensation circuit is ineffective and current
mode instability may occur at duty cycles greater than
50%. To satisfy slope compensation requirements the
minimum inductance is calculated as follows:
LMIN > VOUT
2DCMAX –1
DCMAX
RSENSE 8.33
fSW
The magnetics vendors specify either the saturation cur-
rent, the RMS current or both. When selecting an inductor
based on inductor saturation current, use the peak cur-
rent through the inductor, IOUT(MAX) + DIL/2. The inductor
saturation current specification is the current at which
the inductance, measured at zero current, decreases by
a specified amount, typically 30%.
When selecting an inductor based on RMS current rating,
use the average current through the inductor, IOUT(MAX).
The RMS current specification is the RMS current at which
the part has a specific temperature rise, typically 40°C,
above 25°C ambient.
After calculating the minimum inductance value, the
volt-second product, the saturation current and the RMS
current for your design, select an off-the-shelf inductor.
Contact the Application group at Linear Technology for
further support.
For more detailed information on selecting an inductor,
please see the “Inductor Selection” section of Linear
Technology Application Note 44.
MOSFET Selection
The selection criteria of the external N-channel standard
level power MOSFETs include on resistance (RDS(ON)),
reverse transfer capacitance (CRSS), maximum drain
sourcevoltage(VDSS),totalgatecharge(QG)andmaximum
continuous drain current.
For maximum efficiency, minimize RDS(ON) and CRSS.
Low RDS(ON) minimizes conduction losses while low CRSS
minimizes transition losses. The problem is that RDS(ON)
is inversely related to CRSS. In selecting the top MOSFET
balancing the transition losses with the conduction losses
is a good idea while the bottom MOSFET is dominated by
the conduction loss, which is worse during a short-circit
condition or at a very low duty cycle.
Calculate the maximum conduction losses of the
MOSFETs:
PCOND(TOP) =IOUT(MAX)
2
VOUT
VIN
RDS(ON)
PCOND(BOT) =IOUT(MAX)
2
VIN – VOUT
VIN
RDS(ON)
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| LT3845EFE | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency |
| LT3845EFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標準包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數:1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| LT3845EFE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數:1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LT3845EFEPBF | 制造商:Linear Technology 功能描述:60V Current-Mode Controller Adj. TSSOP16 |
| LT3845EFE-PBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency |
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