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參數(shù)資料
| 型號： | LT1912EMSE#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 4.2 A SWITCHING REGULATOR, 240 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-10 |
| 文件頁數(shù)： | 6/24頁 |
| 文件大?。?/td> | 365K |
| 代理商： | LT1912EMSE#PBF |
LT1912
14
1912fa
the boost capacitor is charged with the energy stored in
the inductor, the circuit will rely on some minimum load
current to get the boost circuit running properly. This
minimum load will depend on input and output volt-
ages, and on the arrangement of the boost circuit. The
minimum load generally goes to zero once the circuit has
started. Figure 5 shows a plot of minimum load to start
and to run as a function of input voltage. In many cases
the discharged output capacitor will present a load to the
switcher, which will allow it to start. The plots show the
worst-case situation where VIN is ramping very slowly.
For lower start-up voltage, the boost diode can be tied to
VIN; however, this restricts the input range to one-half of
the absolute maximum rating of the BOOST pin.
At light loads, the inductor current becomes discontinu-
ous and the effective duty cycle can be very high. This
reduces the minimum input voltage to approximately
300mV above VOUT. At higher load currents, the inductor
current is continuous and the duty cycle is limited by the
maximum duty cycle of the LT1912, requiring a higher
input voltage to maintain regulation.
Soft-Start
The RUN/SS pin can be used to soft-start the LT1912,
reducing the maximum input current during start-up.
The RUN/SS pin is driven through an external RC filter to
create a voltage ramp at this pin. Figure 6 shows the start-
up and shutdown waveforms with the soft-start circuit.
By choosing a large RC time constant, the peak start-up
current can be reduced to the current that is required to
regulate the output, with no overshoot. Choose the value
of the resistor so that it can supply 20A when the RUN/
SS pin reaches 2.5V.
Synchronization
Synchronizing the LT1912 oscillator to an external fre-
quency can be done by connecting a square wave (with
20% to 80% duty cycle) to the SYNC pin. The square
wave amplitude should have valleys that are below 0.3V
and peaks that are above 0.8V (up to 6V).
TheLT1912maybesynchronizedovera250kHzto500kHz
range. The RTresistor should be chosen to set the LT1912
switchingfrequency20%belowthelowestsynchronization
VIN
BOOST
SW
BD
VIN
VOUT
4.7F
C3
GND
LT1912
VIN
BOOST
SW
BD
VIN
VOUT
4.7F
C3
D2
GND
LT1912
VIN
BOOST
SW
BD
VIN
VOUT
4.7F
C3
GND
LT1912
1912 FO4
(4a) For VOUT > 2.8V
(4b) For 2.5V < VOUT < 2.8V
(4c) For VOUT < 2.5V; VIN(MAX) = 30V
Figure 4. Three Circuits For Generating The Boost Voltage
input. For example, if the synchronization signal will be
250kHz and higher, the RT should be chosen for 200kHz.
To assure reliable and safe operation the LT1912 will only
synchronize when the output voltage is near regulation. It
is therefore necessary to choose a large enough inductor
valuetosupplytherequiredoutputcurrentatthefrequency
set by the RT resistor. See Inductor Selection section. It
is also important to note that slope compensation is set
by the RT value: When the sync frequency is much higher
than the one set by RT, the slope compensation will be
significantly reduced which may require a larger inductor
value to prevent subharmonic oscillation.
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| LT1912EMSE-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:36V, 2A, 500kHz Step-Down Switching Regulator |
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| LT1913EDD#PBF | 功能描述:IC REG BUCK ADJ 3.5A 10DFN 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(biāo)準(zhǔn)包裝:250 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V 輸入電壓:2.05 V ~ 6 V PWM 型:電壓模式 頻率 - 開關(guān):2MHz 電流 - 輸出:500mA 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:6-UFDFN 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2 |
| LT1913EDD#TRPBF | 功能描述:IC REG BUCK ADJ 3.5A 10DFN 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:- 設(shè)計(jì)資源:Design Support Tool 標(biāo)準(zhǔn)包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 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:SOT-23-5 細(xì)型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
| LT1913EDD-PBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:25V, 3.5A, 2.4MHz Step-Down Switching Regulator |
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