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參數(shù)資料
| 型號： | LTC3521EUF#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING REGULATOR, 1350 kHz SWITCHING FREQ-MAX, PQCC24 |
| 封裝： | 4 X 4 MM, LEAD FREE, PLASTIC, MO-220WGGD, QFN-24 |
| 文件頁數(shù)： | 3/22頁 |
| 文件大?。?/td> | 1476K |
| 代理商： | LTC3521EUF#TRPBF |
LTC3521
11
3521fa
Soft-Start
The buck converters have an internal voltage mode
soft-start circuit with a nominal duration of 800μs. The
converters remain in regulation during soft-start and will
therefore respond to output load transients which occur
during this time. In addition, the output voltage rise time
has minimal dependency on the size of the output capaci-
tor or load current.
Error Amplifier and Compensation
The LTC3521 buck converters utilize an internal transcon-
ductance error amplifier. Compensation of the feedback
loop is performed internally to reduce the size of the
application circuit and simplify the design process. The
compensation network has been designed to allow use of
a wide range of output capacitors while simultaneously
ensuring rapid response to load transients.
PGOOD Comparators
The PGOOD2 and PGOOD3 pins are open-drain outputs
which indicate the status of the buck converters. If
the buck output voltage falls 9% below the regulation
voltage, the respective PGOOD open-drain output will
pull low. The output voltage must rise 2% above the
falling threshold before the pull-down will turn off. In
addition, there is a 60μs typical deglitching delay in
the flag in order to prevent false trips due to voltage
transients on load steps. The respective PGOOD output
will also pull low during overtemperature shutdown,
undervoltage lockout or if the respective buck con-
verter SHDN pin is pulled low to indicate these fault
conditions.
BUCK-BOOST CONVERTER OPERATION
PWM Mode Operation
When the PWM pin is held high, the LTC3521 buck-boost
converter operates in a constant-frequency PWM mode
with voltage mode control. A proprietary switching algo-
rithm allows the converter to switch between buck, buck-
boost and boost modes without discontinuity in inductor
current or loop characteristics. The switch topology for
the buck-boost converter is shown in Figure 1.
When the input voltage is significantly greater than the
output voltage, the buck-boost converter operates in
buck mode. Switch D turns on continuously and switch
C remains off. Switches A and B are pulse width modu-
lated to produce the required duty cycle to support the
output regulation voltage. As the input voltage decreases,
switch A remains on for a larger portion of the switching
cycle. When the duty cycle reaches approximately 85%,
the switch pair AC begins turning on for a small fraction
of the switching period. As the input voltage decreases
further, the AC switch pair remains on for longer durations
andthedurationoftheBDphasedecreasesproportionally.
As the input voltage drops below the output voltage, the
AC phase will eventually increase to the point that there is
no longer any BD phase. At this point, switch A remains on
continuously while switch pair CD is pulse width modu-
lated to obtain the desired output voltage. At this point,
the converter is operating solely in boost mode.
This switching algorithm provides a seamless transition
between operating modes and eliminates discontinuities
in average inductor current, inductor current ripple and
loop transfer function throughout all three operational
OPERATION
L
D
PGND1B
PGND1A
LTC3521
A
SW1A
SW1B
B
C
3521 F01
VOUT1
PVIN1
Figure 1. Buck-Boost Switch Topology
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3521IFE#PBF | 功能描述:IC REG BUCK BST SYNC ADJ 20TSSOP 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:MIC23xxx HyperLight Load™ Regulators 標(biāo)準(zhǔn)包裝:5,000 系列:HyperLight Load® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.8V 輸入電壓:2.7 V ~ 5.5 V PWM 型:混合物 頻率 - 開關(guān):4MHz 電流 - 輸出:2A 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤，8-MLF? 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-MLF?（2x2） 產(chǎn)品目錄頁面:1094 (CN2011-ZH PDF) 其它名稱:576-3303-2 |
| LTC3521IFE#TRPBF | 功能描述:IC REG BUCK BST SYNC ADJ 20TSSOP 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 |
| LTC3521IUF#PBF | 功能描述:IC REG BUCK BOOST SYNC ADJ 24QFN 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 |
| LTC3521IUF#TRPBF | 功能描述:IC REG BUCK BOOST SYNC ADJ 24QFN 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 |
| LTC3522 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Synchronous 400mA Buck-Boost and 200mA Buck Converters |
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