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參數(shù)資料
| 型號： | LTC3773EUHF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 700 kHz SWITCHING FREQ-MAX, PQCC38 |
| 封裝： | 5 X 7 MM, PLASTIC, MO-220WHKD, QFN-38 |
| 文件頁數(shù)： | 8/32頁 |
| 文件大小： | 461K |
| 代理商： | LTC3773EUHF |
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LTC3773
16
3773fa
mainly depends on the price vs size requirements and any
radiated eld/EMI requirements. New designs for high cur-
rent surface mount inductors are available from numerous
manufacturers, including Coiltronics, Vishay, TDK, Pulse,
Panasonic, Vitec, Coilcraft, Toko and Sumida.
Power MOSFET and Schottky Diode Selection
At least two external power MOSFETs must be selected for
each of the three output sections: One N-channel MOSFET
for the top (main) switch and one or more N-channel
MOSFET(s) for the bottom (synchronous) switch. The
number, type and on-resistance of all MOSFETs selected
take into account the voltage step-down ratio as well as
the actual position (main or synchronous) in which the
MOSFET will be used. A much smaller and much lower
input capacitance MOSFET should be used for the top
MOSFET in applications that have an output voltage that
is less than 1/3 of the input voltage. In applications where
VIN >> VOUT, the top MOSFETs’ on-resistance is normally
less important for overall efciency than its input capaci-
tance at operating frequencies above 300kHz. MOSFET
manufacturers have designed special purpose devices that
provide reasonably low on-resistance with signicantly
reduced input capacitance for the main switch application
in switching regulators.
The peak-to-peak MOSFET gate drive levels are set by
the driver supply voltage, VDR, requiring the use of logic-
level threshold MOSFETs in most applications. Pay close
attention to the BVDSS specication for the MOSFETs as
well; many of the logic-level MOSFETs are limited to 30V
or less.
Selection criteria for the power MOSFETs include the on-
resistance RDS(ON), input capacitance, input voltage and
maximum output current. MOSFET input capacitance is
a combination of several components but can be taken
from the typical “gate charge” curve included on most data
sheets as shown in Figure 2. The curve is generated by
forcing a constant input current into the gate of a common
source, current source loaded stage and then plotting the
gate voltage versus time. The initial slope is the effect of the
gate-to-source and the gate-to-drain capacitance. The at
portion of the curve is the result of the Miller multiplication
effect of the drain-to-gate capacitance as the drain drops the
voltage across the current source load. The upper sloping
line is due to the drain-to-gate accumulation capacitance
and the gate-to-source capacitance.
The Miller charge (the increase in coulombs on the hori-
zontal axis from A to B while the curve is at) is specied
for a given VDS drain voltage, but can be adjusted for
different VDS voltages by multiplying by the ratio of the
application VDS to the curve specied VDS values. A way
to estimate the CMILLER term is to take the change in gate
charge from points A and B on a manufacturers data sheet
and divide by the stated VDS voltage specied. CMILLER
is the most important selection criterion for determining
the transition loss term in the top MOSFET but is not di-
rectly specied on MOSFET data sheets. CRSS and COS are
specied sometimes but denitions of these parameters
are not included.
When the controller is operating in continuous mode the
duty cycles for the top and bottom MOSFETs are given by:
Main Switch Duty Cycle
V
Synchronous Switch Duty Cycle
VV
V
OUT
IN
OUT
IN
=
–
The power dissipation for the main and synchronous
MOSFETs at maximum output current is given by:
P
V
IR
V
I
MAIN
OUT
IN
MAX
DS ON
IN
MAX
=+
+
()(
)
(
()
2
1
2
δ
R
RC
VV
V
DR
MILLER
DR
TH IL
)(
)
–
()
11
+
=+
()
–
()(
)
()
f
P
VV
V
IR
SYNC
IN
OUT
IN
MAX
DS ON
2 1 δ
Figure 2. MOSFET Miller Capacitance
APPLICATIONS INFORMATION
MILLER EFFECT
B
A
VDS
VGS
VIN
QIN
CMILLER = (QB – QA)/VDS
+
–
+
–
3773 F02
VGS
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| LTC3773EUHF#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 38-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 標準包裝: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 |
| LTC3773EUHF#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 38-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® 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 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:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3774EUHE#PBF | 制造商:Linear Technology 功能描述:SWITCHING REG, BUCK, ADJ, 2.2MHZ, DFN-36 |
| LTC3774IUHE#PBF | 制造商:Linear Technology 功能描述:SWITCHING REG, BUCK, ADJ, 2.2MHZ, DFN-36 |
| LTC3775EMSE#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 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:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標準包裝: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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