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参数资料
| 型号： | LTC3851AEMSE#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件页数： | 10/30页 |
| 文件大小： | 430K |
| 代理商： | LTC3851AEMSE#PBF |
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LTC3851A
18
3851afa
applicaTions inForMaTion
The required ESR due to a load current step is:
RESR ≤
ΔV
ΔI
where
Iisthechangeincurrentfromfullloadtozeroload
(or minimum load) and
V is the allowed voltage devia-
tion (not including any droop due to finite capacitance).
The amount of capacitance needed is determined by the
maximum energy stored in the inductor. The capacitance
must be sufficient to absorb the change in inductor
current when a high current to low current transition
occurs. The opposite load current transition is generally
determined by the control loop OPTI-LOOP components,
so make sure not to over compensate and slow down
the response. The minimum capacitance to assure the
inductors’ energy is adequately absorbed is:
COUT >
L ΔI
( )
2
2 ΔV
( )VOUT
where
I is the change in load current.
Manufacturers such as Nichicon, United Chemi-Con and
Sanyo can be considered for high performance through-
hole capacitors. The OS-CON semiconductor electrolyte
capacitor available from Sanyo has the lowest (ESR)
(size) product of any aluminum electrolytic at a somewhat
higher price. An additional ceramic capacitor in parallel
with OS-CON capacitors is recommended to reduce the
inductance effects.
Insurfacemountapplications,ESR,RMScurrenthandling
and load step specifications may require multiple capaci-
tors in parallel. Aluminum electrolytic, dry tantalum and
special polymer capacitors are available in surface mount
packages. Special polymer surface mount capacitors offer
very low ESR but have much lower capacitive density per
unit volume than other capacitor types. These capacitors
offeraverycost-effectiveoutputcapacitorsolutionandare
an ideal choice when combined with a controller having
highloopbandwidth.Tantalumcapacitorsofferthehighest
capacitance density and are often used as output capaci-
tors for switching regulators having controlled soft-start.
Several excellent surge-tested choices are the AVX TPS,
AVX TPSV or the KEMET T510 series of surface mount
tantalums, available in case heights ranging from 1.5mm
to 4.1mm. Aluminum electrolytic capacitors can be used
in cost-driven applications, provided that consideration is
given to ripple current ratings, temperature and long-term
reliability. A typical application will require several to many
aluminum electrolytic capacitors in parallel. A combina-
tion of the above mentioned capacitors will often result
in maximizing performance and minimizing overall cost.
Other capacitor types include Nichicon PL series, NEC
Neocap, Panasonic SP and Sprague 595D series. Consult
manufacturers for other specific recommendations.
Like all components, capacitors are not ideal. Each ca-
pacitor has its own benefits and limitations. Combinations
of different capacitor types have proven to be a very cost
effectivesolution.Rememberalsotoincludehighfrequency
decoupling capacitors. They should be placed as close as
possible to the power pins of the load. Any inductance
presentinthecircuitboardtracesnegatestheirusefulness.
Setting Output Voltage
The LTC3851A output voltage is set by an external feed-
back resistive divider carefully placed across the output,
as shown in Figure 6. The regulated output voltage is
determined by:
ΔIL(SC) = tON(MIN)
VIN
L
To improve the transient response, a feed-forward ca-
pacitor, CFF, may be used. Great care should be taken to
route the VFB line away from noise sources, such as the
inductor or the SW line.
LTC3851A
VFB
VOUT
RB
CFF
RA
3851A F06
Figure 6. Settling Output Voltage
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3851AEUD#PBF | 功能描述:IC REG CTRLR BUCK 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) |
| LTC3851AEUD#TRPBF | 功能描述:IC REG CTRLR BUCK 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) |
| LTC3851AEUD-1#PBF | 功能描述:IC REG CTRLR BUCK 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) |
| LTC3851AEUD-1#TRPBF | 功能描述:IC REG CTRLR BUCK 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) |
| LTC3851AHMSE#PBF | 功能描述:IC REG CTRLR BUCK 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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