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参数资料
| 型号： | LTC3786EMSE#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件页数： | 8/34页 |
| 文件大小： | 397K |
| 代理商： | LTC3786EMSE#TRPBF |
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LTC3786
16
3786fa
applicaTions inForMaTion
Inductor Value Calculation
The operating frequency and inductor selection are in-
terrelated in that higher operating frequencies allow the
use of smaller inductor and capacitor values. Why would
anyone ever choose to operate at lower frequencies with
larger components? The answer is efficiency. A higher
frequency generally results in lower efficiency because
of MOSFET gate charge and switching losses. Also, at
higher frequency, the duty cycle of body diode conduction
is higher, which results in lower efficiency. In addition to
this basic trade-off, the effect of inductor value on ripple
currentandlowcurrentoperationmustalsobeconsidered.
The inductor value has a direct effect on ripple current.
The inductor ripple current
IL decreases with higher
inductance or frequency and increases with higher VIN:
IL =
VIN
f L
1–
VIN
VOUT
Accepting larger values of
IL allows the use of low
inductances, but results in higher output voltage ripple
and greater core losses. A reasonable starting point for
setting ripple current is
IL = 0.3(IMAX). The maximum
IL occurs at VIN = 1/2 VOUT.
The inductor value also has secondary effects. The tran-
sition to Burst Mode operation begins when the average
inductor current required results in a peak current below
25% of the current limit determined by RSENSE. Lower
inductor values (higher
IL) will cause this to occur at
lower load currents, which can cause a dip in efficiency in
the upper range of low current operation. In Burst Mode
operation, lower inductance values will cause the burst
frequency to decrease. Once the value of L is known, an
inductor with low DCR and low core losses should be
selected.
Power MOSFET Selection
Two external power MOSFETs must be selected for the
LTC3786: one N-channel MOSFET for the bottom (main)
switch, and one N-channel MOSFET for the top (synchro-
nous) switch.
The peak-to-peak gate drive levels are set by the INTVCC
voltage. This voltage is typically 5.4V. Consequently, logic-
level threshold MOSFETs must be used in most applica-
tions. Pay close attention to the BVDSS specification 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 manufacturer’s data
sheet. CMILLER is equal to the increase in gate charge
along the horizontal axis while the curve is approximately
flat divided by the specified change in VDS. This result is
then multiplied by the ratio of the application applied VDS
to the gate charge curve specified VDS. When the IC is
operating in continuous mode, the duty cycles for the top
and bottom MOSFETs are given by:
Main Switch Duty Cycle =
VOUT – VIN
VOUT
Synchronous Switch Duty Cycle = VIN
VOUT
IfthemaximumoutputcurrentisIOUT(MAX)andeachchan-
nel takes one-half of the total output current, the MOSFET
power dissipations in each channel at maximum output
current are given by:
PMAIN =
VOUT – VIN
(
)VOUT
VIN2
IOUT(MAX)2 1+ δ
(
)
RDS(ON) +k VOUT3
IOUT(MAX)
VIN
RDR
CMILLER f
PSYNC =
VIN
VOUT
IOUT(MAX)2 1+ δ
(
) RDS(ON)
where
δ is the temperature dependency of RDS(ON)
(approximately 1Ω) is the effective driver resistance at the
MOSFET’s Miller threshold voltage. The constant k, which
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| LTC3786EMSE#PBF | SWITCHING CONTROLLER, 900 kHz SWITCHING FREQ-MAX, PDSO16 |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3786EUD#PBF | 功能描述:IC REG CTRLR BST PWM CM 16-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC3786EUD#PBF | 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 550kHz, QFN16 |
| LTC3786EUD#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 16-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3786IMSE#PBF | 功能描述:IC REG CTRLR BST PWM CM 16-MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3786IMSE#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 16-MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
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