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參數(shù)資料
| 型號： | LTC3859IUHF#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PQCC38 |
| 封裝： | 5 X 7 MM, LEAD FREE, PLASTIC, MO-220WHKD, QFN-38 |
| 文件頁數(shù)： | 16/42頁 |
| 文件大?。?/td> | 624K |
| 代理商： | LTC3859IUHF#TRPBF |
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LTC3859
23
3859fa
APPLICATIONS INFORMATION
The peak-to-peak drive levels are set by the INTVCC voltage.
This voltage is typically 5.4V during start-up (see EXTVCC
Pin Connection). Consequently, logic-level threshold
MOSFETs must be used 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), Miller capacitance CMILLER, input
voltage and maximum output current. Miller capacitance,
CMILLER, can be approximated from the gate charge curve
usually provided on the MOSFET manufacturers’ data
sheet. CMILLER is equal to the increase in gate charge
along the horizontal axis while the curve is approximately
at divided by the specied change in VDS. This result is
then multiplied by the ratio of the application applied VDS
to the gate charge curve specied VDS. When the IC is
operating in continuous mode the duty cycles for the top
and bottom MOSFETs are given by:
Buck Main Switch Duty Cycle =
V
OUT
V
IN
Buck Sync Switch Duty Cycle =
V
IN VOUT
V
IN
Boost Main Switch Duty Cycle
=
V
OUT VIN
V
OUT
Boost Sync Switch Duty Cycle
=
V
IN
V
OUT
The MOSFET power dissipations at maximum output
current are given by:
P
MAIN _ BUCK =
V
OUT
V
IN
I
OUT(MAX)
()2 1+δ
()R
DS(ON) +
(V
IN )
2
I
OUT(MAX)
2
(R
DR )(CMILLER )
1
V
INTVCC VTHMIN
+
1
V
THMIN
(f)
P
SYNC _ BUCK =
V
IN VOUT
V
IN
I
OUT(MAX)
()2 1+δ
()R
DS(ON)
P
MAIN _ BOOST =
V
OUT VIN
(
)V
OUT
V
IN
2
I
OUT(MAX)
(
)2
1
+δ
(
)R
DS(ON) +
V
2
OUT
V
IN
I
OUT(MAX)
2
R
DR
(
) C
MILLER
(
)
1
V
INTVCC VTHMIN
+
1
V
THMIN
(f)
P
SYNC _ BOOST =
V
IN
V
OUT
I
OUT(MAX)
(
)2 1+δ
(
)R
DS(ON)
where
z is the temperature dependency of RDS(ON) and
RDR (approximately 2Ω) is the effective driver resistance
at the MOSFET’s Miller threshold voltage. VTHMIN is the
typical MOSFET minimum threshold voltage.
Both MOSFETs have I2R losses while the main N-channel
equations for the buck and boost controllers include an
additional term for transition losses, which are highest at
high input voltages for the bucks and low input voltages for
the boost. For VIN < 20V (high VIN for the boost) the high
current efciency generally improves with larger MOSFETs,
while for VIN > 20V (low VIN for the boost) the transition
losses rapidly increase to the point that the use of a higher
RDS(ON) device with lower CMILLER actually provides higher
efciency. The synchronous MOSFET losses for the buck
controllers are greatest at high input voltage when the top
switch duty factor is low or during a short-circuit when the
synchronous switch is on close to 100% of the period. The
synchronous MOSFET losses for the boost controller are
greatest when the input voltage approaches the output volt-
age or during an overvoltage event when the synchronous
switch is on 100% of the period.
The term (1+
z) is generally given for a MOSFET in the
form of a normalized RDS(ON) vs Temperature curve, but
z = 0.005/°C can be used as an approximation for low
voltage MOSFETs.
The optional Schottky diodes D4, D5, and D6 shown in
Figure 13 conduct during the dead-time between the
conduction of the two power MOSFETs. This prevents
the body diode of the synchronous MOSFET from turning
on, storing charge during the dead-time and requiring a
reverse recovery period that could cost as much as 3%
in efciency at high VIN. A 1A to 3A Schottky is generally
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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| LTC3860EUH#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-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 |
| LTC3860EUH#PBF | 制造商:Linear Technology 功能描述:BUCK DC/DC CONVERTER IC |
| LTC3860EUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-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(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) |
| LTC3860IUH#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-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(biāo)準(zhǔn)包裝:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無 升壓:是 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR) |
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