參數(shù)資料
型號(hào)： LTC3872ETS8
廠商： LINEAR TECHNOLOGY CORP
元件分類(lèi)： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO8
封裝： 1 MM HEIGHT, PLASTIC, MO-193, TSOT-23, 8 PIN
文件頁(yè)數(shù)： 17/20頁(yè)
文件大?。?/td> 261K
代理商： LTC3872ETS8
LTC3872
6
3872fa
OPERATIO
U
Main Control Loop
The LTC3872 is a No RSENSE constant frequency, current
mode controller for DC/DC boost, SEPIC and yback
converter applications. The LTC3872 is distinguished
from conventional current mode controllers because the
current control loop can be closed by sensing the voltage
drop across the power MOSFET switch or across a discrete
sense resistor, as shown in Figures 1 and 2. This No RSENSE
sensing technique improves efciency, increases power
density and reduces the cost of the overall solution.
For circuit operation, please refer to the Block Diagram
of the IC and the Typical Application on the front page. In
normal operation, the power MOSFET is turned on when
the oscillator sets the RS latch and is turned off when the
current comparator resets the latch. The divided-down
output voltage is compared to an internal 1.2V reference by
the error amplier, which outputs an error signal at the ITH
pin. The voltage on the ITH pin sets the current comparator
input threshold. When the load current increases, a fall in
the FB voltage relative to the reference voltage causes the
ITH pin to rise, which causes the current comparator to
trip at a higher peak inductor current value. The average
inductor current will therefore rise until it equals the load
current, thereby maintaining output regulation.
The LTC3872 can be used either by sensing the voltage
drop across the power MOSFET or by connecting the SW
pin to a conventional sensing resistor in the source of the
power MOSFET. Sensing the voltage across the power
MOSFET maximizes converter efciency and minimizes the
component count; the maximum rating for this pin, 60V,
allows MOSFET sensing in a wide output voltage range.
The RUN/SS pin controls whether the IC is enabled or is in
a low current shutdown state. With the RUN/SS pin below
0.85V, the chip is off and the input supply current is typi-
cally only 10μA. With an external capacitor connected to
the RUN/SS pin an optional external soft-start is enabled.
A 0.7μA trickle current will charge the capacitor, pulling
the RUN/SS pin above shutdown threshold and slowly
ramping RUN/SS to limit the VITH during start-up. Because
the noise on the SW pin could couple into the RUN/SS
pin, disrupting the trickle charge current that charges the
RUN/SS pin, a 1M resistor is recommended to pull-up the
RUN/SS pin when external soft-start is used. When RUN/SS
is driven by an external logic, a minimum of 2.75V logic is
recommended to allow the maximum ITH range.
Light Load Operation
Under very light load current conditions, the ITH pin volt-
age will be very close to the zero current level of 0.85V.
As the load current decreases further, an internal offset at
the current comparator input will assure that the current
comparator remains tripped (even at zero load current) and
the regulator will start to skip cycles, as it must, in order
to maintain regulation. This behavior allows the regulator
to maintain constant frequency down to very light loads,
resulting in low output ripple as well as low audible noise
and reduced RF interference, while providing high light
load efciency.
Figure 1. SW Pin (Internal Sense Pin)
Connection for Maximum Efciency
COUT
VSW
VOUT
VIN
GND
L
D
+
NGATE
GND
VIN
SW
3872 F01
LTC3872
COUT
VSW
RSENSE
VOUT
VIN
GND
L
D
+
NGATE
GND
VIN
SW
3872 F02
LTC3872
Figure 2. SW Pin (Internal Sense Pin)
Connection for Sensing Resistor
相關(guān)PDF資料
PDF描述
LTC3872EDDB#TRM SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO8
LTC3872ITS8#PBF SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO8
LTC3872ITS8#TRPBF SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO8
LTC3872HTS8#TRPBF SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO8
LTC3872HTS8#PBF SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO8
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC3872ETS8#PBF 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Up 2.75V to 9.8V Input 8-Pin TSOT-23 制造商:Linear Technology 功能描述:BOOST 9.8VIN 550KHZ 60V 8TSOT23 制造商:Linear Technology 功能描述:BOOST, 9.8VIN, 550KHZ, 60V, 8TSOT23 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, BOOST, 550KHZ, TSOT-23-8; Primary Input Voltage:9.8V; No. of Outputs:1; Output Current:10A; No. of Pins:8; Operating Temperature Min:-40C; Operating Temperature Max:85C; Package / Case:8-TSOT-23 ;RoHS Compliant: Yes 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, BOOST, 550KHZ, TSOT-23-8; Primary Input Voltage:9.8V; No. of Outputs:1; No. of Pins:8; Operating Temperature Min:-40C; Operating Temperature Max:85C; Package / Case:8-TSOT-23 ;RoHS Compliant: Yes
LTC3872ETS8#TRMPBF 功能描述:IC REG CTRLR BST PWM CM TSOT23-8 RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 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(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤(pán) 包裝:Digi-Reel® 產(chǎn)品目錄頁(yè)面:1303 (CN2011-ZH PDF) 其它名稱(chēng):LM3754SQDKR
LTC3872ETS8#TRPBF 功能描述:IC REG CTRLR BST PWM CM TSOT23-8 RoHS:是 類(lèi)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(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC3872HDDB#TRMPBF 功能描述:IC REG CTRLR BST PWM CM 8-DFN RoHS:是 類(lèi)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(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LTC3872HDDB#TRPBF 功能描述:IC REG CTRLR BST PWM CM 8-DFN RoHS:是 類(lèi)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(wú) 升壓:是 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
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