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參數資料
| 型號： | LTC3785EUF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC24 |
| 封裝： | 4 X 4 MM, PLASTIC, MO-220WGGD, QFN-24 |
| 文件頁數： | 7/20頁 |
| 文件大?。?/td> | 275K |
| 代理商： | LTC3785EUF |
LTC3785
3785fc
applicaTions inForMaTion
EFFICIENCY CONSIDERATIONS
The percentage efficiency of a switching regulator is
equal to the output power divided by the input power
times 100%.
It is often useful to analyze individual losses to determine
what is limiting the efficiency and which change would
produce the most improvement. Although all dissipative
elements in circuits produce losses, four main sources
account for most of the losses in LTC3785 application
circuits:
1. DC I2R losses. These arise from the resistances of the
MOSFETs, sensing resistor (if used), inductor and PC
board traces and cause the efficiency to drop at high
output currents.
2. Transition loss. This loss arises from the brief voltage
transition time of switch A or switch C. It depends upon
theswitchvoltage,inductorcurrent,driverstrengthand
MOSFET capacitance, among other factors.
Transition Loss ~ VSW2 IL CRSS f
where CRSS is the reverse transfer capacitance.
3. CIN and COUT loss. The input capacitor has the difficult
job of filtering the large RMS input current to the regula-
tor in buck mode. The output capacitor has the more
difficult job of filtering the large RMS output current
in boost mode. Both CIN and COUT are required to have
low ESR to minimize the AC I2R loss and sufficient
capacitance to prevent the RMS current from causing
additional upstream losses in fuses or batteries.
4. Other losses. Optional Schottky diodes D1 and D2 are
responsible for conduction losses during dead time
and light load conduction periods. Core loss is the
predominant inductor loss at light loads. Turning on
switch C causes reverse recovery current loss in boost
mode.Whenmakingadjustmentstoimproveefficiency,
the input current is the best indicator of changes in
efficiency. If you make a change and the input current
decreases, then the efficiency has increased. If there
is no change in input current, then there is no change
in efficiency.
5. VCC regulator loss. In applications where the input
voltage is above 5V, such as two Li-Ion cells, the VCC
regulator will dissipate some power due the differential
voltage and the average output current to the drive the
gates of the output switches. The VCC pin can be driven
directly from a high efficiency external 5V source if
desired to incrementally improve overall efficiency at
lighter loads.
DESIGN EXAMPLE
As a design example, assume VIN = 2.7V to 10V (3.6V
nominal Li-Ion with 9V adapter), VOUT = 3.3V (5%),
IOUT(MAX) = 3A and f = 500kHz.
Determine the Inductor Value
SettingtheInductorRippleto40%andusingtheequations
in the Inductor Selection section gives:
L
>
2.7
( )2 3.3–2.7
(
)100
500 103 3 40 3.3
( )2
= 0.67H
L
>
3.3 10 – 3.3
(
)100
500 103 3 40 10
= 3.7H
So the worst-case ripple for this application is during buck
mode so a standard inductor value of 3.3H is chosen.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LTC3785EUF#PBF | 功能描述:IC REG CTRLR BST PWM VM 24-QFN 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 |
| LTC3785EUF#TRPBF | 功能描述:IC REG CTRLR BST PWM VM 24-QFN 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) |
| LTC3785EUF-1#PBF | 功能描述:IC REG CTRLR BST PWM VM 24-QFN 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) |
| LTC3785EUF-1#TRPBF | 功能描述:IC REG CTRLR BST PWM VM 24-QFN 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:4,500 系列:PowerWise® PWM 型:控制器 輸出數:1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 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:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3785EUFPBF | 制造商:Linear Technology 功能描述:10V Synch Buck-Boost Controller LTC3785 |
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