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參數(shù)資料
| 型號： | LT3494EDDB |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.25 A SWITCHING REGULATOR, PDSO8 |
| 封裝： | 3 X 2 MM, PLASTIC, MO-229WECD-1, DFN-8 |
| 文件頁數(shù)： | 10/12頁 |
| 文件大?。?/td> | 261K |
| 代理商： | LT3494EDDB |
LT3494/LT3494A
7
3494fb
OPERATION
The LT3494/LT3494A use a novel control scheme to pro-
vide high efciency over a wide range of output current.
In addition, this technique keeps the switching frequency
above the audio band over all load conditions.
The operation of the part can be better understood by
refering to the Block Diagram. The part senses the output
voltage by monitoring the voltage on the FB pin. The user
sets the desired output voltage by choosing the value of
the external top feedback resistor. The parts incorporate
a precision 182k bottom feedback resistor. Assuming that
output voltage adjustment is not used (CTRL pin is tied to
1.5V or greater), the internal reference (VREF = 1.225V) sets
the voltage at which FB will servo to during regulation.
The Switch Control block senses the output of the ampli-
er and adjusts the switching frequency as well as other
parameters to achieve regulation. During the start-up of
the circuit, special precautions are taken to insure that the
inductor current remains under control.
Because the switching frequency is never allowed to fall
below approximately 50kHz, a minimum load must be
present to prevent the output voltage from drifting too high.
This minimum load is automatically generated within the
part via the Shunt Control block. The level of this current
is adaptable, removing itself when not needed to improve
efciency at higher load levels.
The LT3494/LT3494A also have an integrated Schottky
diode and PMOS output disconnect switch. The PMOS
switch is turned on when the part is enabled via the SHDN
pin. When the parts are in shutdown, the PMOS switch
turns off, allowing the VOUT node to go to ground. This
type of disconnect function is often required in power
supplies.
The only difference between the LT3494A and LT3494
is the level of the current limit. The LT3494A has a typi-
cal peak current limit of 350mA while the LT3494 has a
180mA limit.
APPLICATIONS INFORMATION
Choosing an Inductor
Several recommended inductors that work well with the
LT3494/LT3494A are listed in Table 1, although there are
many other manufacturers and devices that can be used.
Consult each manufacturer for more detailed information
and for their entire selection of related parts. Many dif-
ferent sizes and shapes are available. Use the equations
and recommendations in the next few sections to nd the
correct inductance value for your design.
Inductor Selection—Boost Regulator
The formula below calculates the appropriate inductor
value to be used for a boost regulator using the LT3494/
LT3494A (or at least provides a good starting point).
This value provides a good trade off in inductor size and
system performance. Pick a standard inductor close to
this value. A larger value can be used to slightly increase
the available output current, but limit it to around twice
the value calculated below, as too large of an inductance
will decrease the output voltage ripple without providing
much additional output current. A smaller value can be
used (especially for systems with output voltages greater
than 12V) to give a smaller physical size. Inductance can
be calculated as:
L = (VOUT – VIN(MIN) + 0.5V) 0.66 (μH)
where VOUT is the desired output voltage and VIN(MIN) is
the minimum input voltage. Generally, a 10μH or 15μH
inductor is a good choice.
Table 1. Recommended Inductors
PART
FOR USE WITH
VALUE
(μH)
MAX DCR
(
Ω)
MAX DC I
(mA)
SIZE
(mm
× mm × mm) VENDOR
LQH32CN100K53
LQH32CN150K53
LT3494/LT3494A
LT3494
10
15
0.3
0.58
450
300
3.5
× 2.7 × 1.7
3.5
× 2.7 × 1.7
Murata
www.murata.com
CDRH3D11-100
CDHED13/S-150
LT3494
LT3494/LT3494A
10
15
0.24
0.55
280
550
4.0
× 4.0 × 1.2
4.0
× 4.2 × 1.4
Sumida
www.sumida.com
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LT3494EDDB#PBF | 制造商:Linear Technology 功能描述:DC-DC CONVERTER BOOST DFN-8 制造商:Linear Technology 功能描述:DC-DC CONVERTER, BOOST, DFN-8; Primary Input Voltage:16V; No. of Outputs:1; Output Current:180mA; No. of Pins:8; Operating Temperature Min:-40C; Operating Temperature Max:85C; Package / Case:8-DFN; Supply Voltage Max:16V ;RoHS Compliant: Yes |
| LT3494EDDB#TRM | 制造商:Linear Technology 功能描述:MICROPOWER LOW NOISE BOOST CONVERTERS WITH OUTPUT DISCONNECT |
| LT3494EDDB#TRMPBF | 功能描述:IC REG BOOST ADJ 0.18A 8DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 產(chǎn)品培訓(xùn)模塊:High Efficiency Current Mode Switching Regulators CMOS LDO Regulators 特色產(chǎn)品:BD91x Series Step-Down Regulators 標準包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:兩者兼有 輸出數(shù):2 輸出電壓:3.3V，0.8 V ~ 2.5 V 輸入電壓:4.5 V ~ 5.5 V PWM 型:電流模式 頻率 - 開關(guān):1MHz 電流 - 輸出:1.5A 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:20-VFQFN 裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:VQFN020V4040 產(chǎn)品目錄頁面:1373 (CN2011-ZH PDF) 其它名稱:BD9152MUV-E2TR |
| LT3494EDDB#TRPBF | 功能描述:IC REG BOOST ADJ 0.18A 8DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標準包裝:500 系列:- 類型:切換式電容器（充電泵），反相 輸出類型:固定 輸出數(shù):1 輸出電壓:-3V 輸入電壓:2.3 V ~ 5.5 V PWM 型:Burst Mode? 頻率 - 開關(guān):900kHz 電流 - 輸出:100mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-6 細型，TSOT-23-6 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:TSOT-23-6 其它名稱:LTC1983ES6-3#TRMTR |
| LT3494EDDBTRMPBF | 制造商:Linear Technology 功能描述:Boost Converter uPower Low Noise DFN8EP |
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