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參數(shù)資料
| 型號： | LT3845AMPFE#PBF |
| 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(shù)： | 6/26頁 |
| 文件大小： | 284K |
| 代理商： | LT3845AMPFE#PBF |
LT3845A
14
3845afa
APPLICATIONS INFORMATION
ground, as shown in Figure 2. The nominal voltage on the
fSET pin is 1V and the current that flows from this pin is
used to charge an internal oscillator capacitor. The value
of RSET for a given operating frequency can be chosen
from Figure 2 or from the following equation:
RSET(kΩ) = 8.4 104 fSW(–1.31)
FREQUENCY (kHz)
0
20
R
SET
(k)
40
80
100
120
400
200
3845A F2
60
200
100
500
300
600
140
160
180
Figure 2. Timing Resistor (RSET) Value
RSENSE Selection
The current sense resistor, RSENSE, monitors the inductor
current of the supply (See Typical Application on front
page). Its value is chosen based on the maximum required
output load current. The LT3845A current sense amplifier
has a maximum voltage threshold dependent on duty
cycle. The maximum peak current is calculated as follows:
IPEAK(MAX) =
100mV – 45mV
VOUT
VIN
RSENSE
The maximum output load current, IOUT(MAX), is the peak
inductor current minus half the peak-to-peak ripple cur-
rent,
DI.
Typical values for RSENSE are in the range of 0.005Ω
to 0.05Ω.
Operating Frequency
The choice of operating frequency is a trade off between
efficiency and component size. Low frequency operation
improvesefficiencybyreducingMOSFETswitchinglosses
andgatechargelosses.However,lowerfrequencyoperation
requires more inductance for a given amount of ripple
current, resulting in a larger inductor size and higher cost.
If the ripple current is allowed to increase, larger output
capacitors may be required to maintain the same output
ripple. For converters with high step-down VIN to VOUT
ratios, another consideration is the minimum on-time of
the LT3845A (see the Minimum On-time Considerations
section). A final consideration for operating frequency is
thatinnoise-sensitivecommunicationssystems,itisoften
desirable to keep the switching noise out of a sensitive
frequency band. The LT3845A uses a constant frequency
architecture that can be programmed over a 100kHz to
500kHz range with a single resistor from the fSET pin to
Table 1 lists typical resistor values for common operating
frequencies.
Table 1. Recommended 1% Standard Values
RSET (kΩ)
fSW (kHz)
191
100
118
150
80.6
200
63.4
250
49.9
300
40.2
350
33.2
400
27.4
450
23.2
500
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| 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(shù):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(shù):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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