参数资料
| 型号： | LTC3786EUD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/34页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 16-QFN |
| 标准包装： | 121 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 850kHz |
| 占空比： | 100% |
| 电源电压： | 4.5 V ~ 38 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： | 16-WFQFN 裸露焊盘 |
| 包装： | 管件 |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页当前第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页第33页第34页
LTC3786
APPLICATIONS INFORMATION
V IN ? V IN ?
? I L = ? 1 – ?
V OUT – V IN
V IN
? I OUT(MAX)2 ? ( 1 + δ )
( V OUT – V IN ) V OUT
P MAIN =
? R DS(ON) + k ? V OUT 3 ?
I OUT(MAX)
V IN
? I OUT(MAX)2 ? ( ) ? R DS(ON)
P SYNC =
V IN
InductorValueCalculation
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
current and low current operation must also be considered.
The inductor value has a direct effect on ripple current.
The inductor ripple current ? I L decreases with higher
inductance or frequency and increases with higher V IN :
f ? L ? V OUT ?
Accepting larger values of ? I L 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 ? I L = 0.3(I MAX ). The maximum
? I L occurs at V IN = 1/2 V OUT .
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 R SENSE . Lower
inductor values (higher ? I L ) 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 INTV CC
voltage. This voltage is typically 5.4V. Consequently, logic-
level threshold MOSFETs must be used in most applica-
tions. Pay close attention to the BV DSS 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, R DS(ON) , Miller capacitance, C MILLER , input
voltage and maximum output current. Miller capacitance,
C MILLER , can be approximated from the gate charge curve
usually provided on the MOSFET manufacturer’s data
sheet. C MILLER is equal to the increase in gate charge
along the horizontal axis while the curve is approximately
flat divided by the specified change in V DS . This result is
then multiplied by the ratio of the application applied V DS
to the gate charge curve specified V DS . When the IC is
operating in continuous mode, the duty cycles for the top
and bottom MOSFETs are given by:
Main Switch Duty Cycle =
V OUT
Synchronous Switch Duty Cycle =
V OUT
If the maximum output current is I OUT(MAX) and each chan-
nel takes one-half of the total output current, the MOSFET
power dissipations in each channel at maximum output
current are given by:
V IN2
? R DR
? C MILLER ? f
1 + δ
V OUT
where δ is the temperature dependency of R DS(ON)
(approximately 1Ω) is the effective driver resistance at the
MOSFET’s Miller threshold voltage. The constant k, which
3786fa
16
相关PDF资料 |
PDF描述 |
|---|---|
| LTC3787EUFD#PBF | IC REG CTRLR BST PWM CM 28-QFN |
| LTC3788IUH#TRPBF | IC REG CTRLR BST PWM CM 32-QFN |
| LTC3789EGN#PBF | IC REG CTRLR BST PWM CM 28-SSOP |
| LTC3801BES6#TRM | IC REG CTRLR BUCK PWM TSOT23-6 |
| LTC3802EGN | IC REG CTRLR BUCK PWM VM 28-SSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| 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) |
| LTC3786IUD#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:- 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) |
| LTC3786IUD#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) |
| LTC3787EGN#PBF | 功能描述:IC REG CTRLR BST PWM CM 28-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
发布紧急采购，3分钟左右您将得到回复。