- 您现在的位置：买卖IC网 > PDF目录15323 > LTC3808EDE#PBF (Linear Technology)IC REG CTRLR BUCK PWM CM 14-DFN PDF资料下载
参数资料
| 型号： | LTC3808EDE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 16/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 14-DFN |
| 标准包装： | 91 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 825kHz |
| 占空比： | 100% |
| 电源电压： | 2.75 V ~ 9.8 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： | -40°C ~ 85°C |
| 封装/外壳： | 14-WFDFN 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
LTC3808
APPLICATIO S I FOR ATIO
The corresponding average current depends on the amount
of ripple current. Lower inductor values (higher I RIPPLE )
will reduce the load current at which Burst Mode operation
begins.
The ripple current is normally set so that the inductor
current is continuous during the burst periods. Therefore,
I RIPPLE ≤ I BURST(PEAK)
This implies a minimum inductance of:
inductors wound on bobbins are generally easier to sur-
face mount. However, designs for surface mount that do
not increase the height significantly are available from
Coiltronics, Coilcraft, Dale and Sumida.
Schottky Diode Selection (Optional)
The schottky diode D in Figure 12 conducts current during
the dead time between the conduction of the power
MOSFETs. This prevents the body diode of the bottom
N-channel MOSFET from turning on and storing charge
? OUT
L MIN ≤
V IN – V OUT
f OSC ? I BURST ( PEAK )
V
V IN
during the dead time, which could cost as much as 1% in
efficiency.A1ASchottkydiodeisgenerallyagoodsizefor
A smaller value than L MIN could be used in the circuit,
although the inductor current will not be continuous
during burst periods, which will result in slightly lower
efficiency. In general, though, it is a good idea to keep
I RIPPLE comparable to I BURST(PEAK) .
Inductor Core Selection
Once the value of L is known, the type of inductor must be
selected. High efficiency converters generally cannot afford
the core loss found in low cost powdered iron cores, forc-
ing the use of more expensive ferrite, molypermalloy or Kool
M μ ? cores. Actual core loss is independent of core size for
most LTC3808 applications, since it conducts a relatively
small average current. Larger diode results in additional
transition losses due to its larger junction capacitance.
This diode may be omitted if the efficiency loss can be
tolerated.
C IN and C OUT Selection
In continuous mode, the source current of the P-channel
MOSFET is a square wave of duty cycle (V OUT /V IN ). To
prevent large voltage transients, a low ESR input capacitor
sized for the maximum RMS current must be used. The
maximum RMS capacitor current is given by:
V OUT IN OUT )
? ( V – V
afixedinductorvalue,butisverydependentontheinduc-
tance selected. As inductance increases, core losses go
down. Unfortunately, increased inductance requires more
C IN Re quiredI RMS ≈ I MAX ?
V IN
1 / 2
turns of wire and therefore copper losses will increase.
Ferrite designs have very low core losses and are preferred
at high switching frequencies, so design goals can con-
centrate on copper loss and preventing saturation. Ferrite
core material saturates “hard”, which means that induc-
tance collapses abruptly when the peak design current is
exceeded. Core saturation results in an abrupt increase in
inductor ripple current and consequent output voltage
ripple. Do not allow the core to saturate!
Molypermalloy (from Magnetics, Inc.) is a very good, low
loss core material for toroids, but is more expensive than
ferrite. A reasonable compromise from the same manu-
facturer is Kool M μ . Toroids are very space efficient,
especially when several layers of wire can be used, while
This formula has a maximum value at V IN = 2V OUT , where
I RMS = I OUT /2. This simple worst-case condition is com-
monly used for design because even significant deviations
do not offer much relief. Note that capacitor manufacturer’s
ripple current ratings are often based on 2000 hours of life.
This makes it advisable to further derate the capacitor or
to choose a capacitor rated at a higher temperature than
required. Several capacitors may be paralleled to meet the
size or height requirements in the design. Due to the high
operating frequency of the LTC3808, ceramic capacitors
can also be used for C IN . Always consult the manufacturer
if there is any question.
The selection of C OUT is driven by the effective series
resistance (ESR). Typically, once the ESR requirement is
Kool M μ is a registered trademark of Magnetics, Inc.
3808f
16
相关PDF资料 |
PDF描述 |
|---|---|
| UCA2G220MHD6TN | CAP ALUM 22UF 400V 20% RADIAL |
| ESC28DREH-S13 | CONN EDGECARD 56POS .100 EXTEND |
| LTC690IS8#TR | IC SUPERVISORY CIRCUIT MPU 8SOIC |
| LTC1778EGN-1 | IC REG CTRLR BUCK PWM CM 16-SSOP |
| LTC1778EGN#PBF | IC REG CTRLR BUCK PWM CM 16-SSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3808EGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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) |
| LTC3808EGN#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP 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) |
| LTC3809EDD | 功能描述:IC REG CTRLR BUCK PWM CM 10-DFN RoHS:否 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) |
| LTC3809EDD#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 10-DFN 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 |
| LTC3809EDD#TR | 功能描述:IC REG CTRLR BUCK PWM CM 10-DFN RoHS:否 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) |
发布紧急采购，3分钟左右您将得到回复。