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参数资料
| 型号： | LTC3811EUHF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 31/48页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 38-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 850kHz |
| 占空比： | 90% |
| 电源电压： | 4.5 V ~ 30 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： | 38-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3811
APPLICATIONS INFORMATION
use type III compensation effectively removes constraints
on output capacitor ESR. The impedance characteristics
of each capacitor type are signi?cantly different than an
ideal capacitor and therefore require accurate modeling
and bench evaluation during design.
providing a linear ramping voltage at the SS/TRACK pin.
The LTC3811 will regulate the V FB pin (and hence V OUT )
according to the voltage on the SS/TRACK pin, allowing
V OUT to rise smoothly from 0V to its ?nal regulated value.
The total soft-start time will be approximately:
Manufacturers such as Nichicon, United Chemicon and
Sanyo should be considered for high performance through-
hole capacitors. The OS-CON semiconductor dielectric
t SS = C SS ?
0.6V
2.5 μ A
capacitor available from Sanyo and the Panasonic SP
surface mount types have the lowest (ESR)(size) product
of any aluminum electrolytic at a somewhat higher price.
An additional ceramic capacitor in parallel with OS-CON
type capacitors is recommended to reduce inductance
effects.
In surface mount applications, multiple capacitors may
Alternatively, the SS/TRACK pin can be used to track two
(or more) supplies during start-up, as shown qualitatively
in Figures 19a and 19b. To do this, a resistor divider
should be connected from the master supply (V X ) to the
SS/TRACK pin of the slave supply (V OUT ), as shown in
Figure 20. During start-up V OUT will track V X according
to the ratio set by the resistor divider:
= TRACKA ?
have to be paralleled to meet the ESR or RMS current
handling requirements of the application. Aluminum
electrolytic and dry tantalum capacitors are both available
V OUT
V X
R
R A
R A + R B
R TRACKA + R TRACKB
in surface mount con?gurations. New special polymer
surface mount capacitors offer very low ESR also but
have much lower capacitive density per unit volume. In
the case of tantalum, it is critical that the capacitors are
surge tested for use in switching power supplies. Several
excellent choices are the AVX TPS, AVX TPSV or the KEMET
T510 series of surface mount tantalums, available in case
heights ranging from 2mm to 4mm. Other capacitor types
include Sanyo OS-CON, Nichicon PL series and Sprague
595D series. Consult the manufacturer for other speci?c
recommendations. A combination of capacitors will often
result in maximizing performance and minimizing overall
cost and size.
Tracking and Soft-Start (SS/TRACK Pins)
The start-up of each V OUT is controlled by the voltage on
the respective SS/TRACK pin. When the voltage on the
SS/TRACK pin is less than the internal 0.6V reference,
the LTC3811 regulates the V FB pin voltage to the voltage
For coincident tracking (V OUT = V X during start-up),
R A = R TRACKA
R B = R TRACKB
Note that the small SS/TRACK charging current is always
?owing, producing a small offset error. To minimize this
error, select the tracking resistor divider values to be small
enough to make this error negligible.
Topside MOSFET Driver Supply (C B , D B )
External bootstrap capacitors C B connected to the BOOST
and SW pins supply the gate drive voltages for the topside
MOSFETs. Capacitor C B in the Functional Diagram is
charged though external diode D B from DRV CC when the
SW pin is low. When one of the topside MOSFETs is to
be turned on, the driver places the C B voltage across the
gate-source of the desired MOSFET. This enhances the
MOSFET and turns on the topside switch. The switch
on the SS/TRACK pin instead of 0.6V. The SS/TRACK pin
can be used to program an external soft-start function or
to allow V OUT to “track” another supply during start-up.
C SS
LTC3811
SS/TRACK
Soft-start is enabled by simply connecting a capacitor from
the SS/TRACK pin to ground, as shown in Figure 18. An
SGND
3811 F18
internal 2.5μA current source charges up the capacitor,
Figure 18. Using the SS/TRACK pin to Program Soft-Start
3811f
31
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相关代理商/技术参数 |
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| LTC3812EFE5#PBF | 制造商:Linear Technology 功能描述: |
| LTC3812EFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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 |
| LTC3812EFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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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