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參數(shù)資料
| 型號： | LTC3879EUD#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, PQCC16 |
| 封裝： | 3 X 3 MM, LEAD FREE, PLASTIC, MO-220WEED-4, QFN-16 |
| 文件頁數(shù)： | 2/28頁 |
| 文件大?。?/td> | 302K |
| 代理商： | LTC3879EUD#TRPBF |
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LTC3879
10
3879f
OPERATION
Main Control Loop
The LTC3879 is a valley current mode controller IC for
use in DC/DC step-down converters. In normal continu-
ous operation, the top MOSFET is turned on for a xed
interval determined by a one-shot timer, OST. When the
top MOSFET is turned off, the bottom MOSFET is turned
on until the current comparator, ICMP, trips, restarting
the one-shot timer and initiating the next cycle. Inductor
valley current is measured by sensing the voltage between
the PGND and SW pins using the bottom MOSFET on-
resistance. The voltage on the ITH pin sets the compara-
tor threshold corresponding to inductor valley current.
The error amplier EA adjusts this voltage by comparing
the feedback signal VFB from the output voltage to the
feedback reference voltage VFBREF. Increasing the load
current causes a drop in the feedback voltage relative
to the reference. The EA senses the feedback voltage
drop and adjusts the ITH voltage higher until the average
inductor current matches the load current.
With DC current loads less than 1/2 of the peak-to-peak
ripple the inductor current can drop to zero or become
negative. In discontinuous operation, negative inductor
current is detected and prevented by the current reversal
comparator IREV,whichshutsoffMB.Bothswitchesremain
off with the output capacitor supplying the load current
until the EA moves the ITH voltage above the zero current
level (0.8V) to initiate another switching cycle. When the
MODE pin is below the internal threshold reference, VMODE,
the regulator is forced to operate in continuous mode by
disabling reversal comparator, IREV, thereby allowing the
inductor current to become negative.
The continuous mode operating frequency can be deter-
mined by dividing the calculated duty cycle, VOUT/VIN,
by the xed on-time. The OST generates an on-time
proportional to the ideal duty cycle, thus holding the
frequency approximately constant with changes in VIN.
The nominal frequency can be adjusted with an external
resistor, RON.
Foldback current limiting is provided to protect against
low impedance shorts. If the controller is in current limit
and VOUT drops to less 50% of regulation, the current limit
set-point “folds back” to progressively lower values. To
recover from foldback current limit, the excessive load or
low impedance short needs to be removed.
When RUN is less than 0.7V, the LTC3879 is in the low
power shutdown state with a nominal bias current of
18μA. When RUN is greater than 0.7V and less than 1.5V,
INTVCC and all internal circuitry are enabled while TG and
BG are forced low. When RUN is taken greater than 1.5V,
switching begins and the TRACK/SS pin is released from
ground. The output voltage follows the TRACK/SS input
multiplied by feedback factor when TRACK/SS is less than
0.6V. Soft-start is complete when TRACK/SS exceeds the
internal 0.6V reference voltage and regulates normally.
相關(guān)PDF資料 |
PDF描述 |
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| LTC3879IUD#PBF | SWITCHING CONTROLLER, PQCC16 |
| LTC3880IUJ-1#TRPBF | 0.1 A DUAL SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC40 |
| LTC3880IUJ#PBF | 0.1 A DUAL SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC40 |
| LTC3880EUJ-1#TRPBF | 0.1 A DUAL SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC40 |
| LTC3880EUJ-1#PBF | 0.1 A DUAL SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC40 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3879IMSE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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) |
| LTC3879IMSE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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) |
| LTC3879IUD#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-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(biāo)準(zhǔn)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) |
| LTC3879IUD#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-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(biāo)準(zhǔn)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) |
| LTC3880EUJ#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 40-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標(biāo)準(zhǔn)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(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
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