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参数资料
| 型号： | LTC1147CS8-5#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 9/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 8-SOIC |
| 标准包装： | 100 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 占空比： | 100% |
| 电源电压： | 3.5 V ~ 14 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： | 0°C ~ 70°C |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1332 (CN2011-ZH PDF) |
LTC1147-3.3
LTC1147-5/LTC1147L
APPLICATIO S I FOR ATIO
used. For V IN > 8V, a standard threshold MOSFET (V GS(TH)
< 4V) may be used. If V IN is expected to drop below 8V,
a logic-level threshold MOSFET (V GS(TH) < 2.5V) is
I D1 =
( V IN – V OUT + V D )
V IN
(I LOAD )
strongly recommended. When a logic-level MOSFET is
used, the LTC1147 supply voltage must be less than the
absolute maximum V GS ratings for the MOSFET.
The maximum output current I MAX determines the R DS(ON)
requirement for the power MOSFET. When the LTC1147
series is operating in continuous mode, the simplifying
Remember to keep lead lengths short and observe proper
grounding (see Board Layout Checklist) to avoid ringing
and increased dissipation.
The forward voltage drop allowable in the diode is calcu-
lated from the maximum short-circuit current as:
assumption can be made that either the MOSFET or
Schottky diode is always conducting the average load
V F ≈
P D
I SC(PK)
P-Ch Duty Cycle = OUT
(V IN – V OUT + V D )
(V IN )(P P )
(V OUT )(I MAX2 )(1 + δ P )
C IN Required I RMS ≈ I MAX
current. The duty cycles for the MOSFET and diode are
given by:
V
V IN
Schottky Diode Duty Cycle =
V IN
From the duty cycle the required R DS(ON) for the MOSFET
can be derived:
P-Ch R DS(ON) =
where P P is the allowable power dissipation and δ P is the
temperature dependency of R DS(ON) . P P will be deter-
mined by efficiency and/or thermal requirements (see
Efficiency Considerations). (1 + δ ) is generally given for a
MOSFET in the form of a normalized R DS(ON) vs tempera-
ture curve, but δ = 0.007/ ° C can be used as an approxima-
tion for low voltage MOSFETs.
Output Diode Selection (D1)
The Schottky diode D1 shown in Figure 1 only conducts
during the off-time. It is important to adequately specify
the diode peak current and average power dissipation so
as not to exceed the diode ratings.
The most stressful condition for the output diode is under
short circuit (V OUT = 0V). Under this condition the diode
must safely handle I SC(PK) at close to 100% duty cycle.
Under normal load conditions the average current con-
ducted by the diode is:
where P D is the allowable power dissipation and will be
determined by efficiency and/or thermal requirements
(see Efficiency Considerations).
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 capaci-
tor sized for the maximum RMS current must be used. The
maximum RMS capacitor current is given by:
[V OUT (V IN – V OUT )] 1/2
V IN
This formula has a maximum 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 devia-
tions do not offer much relief. Note that capacitor
manufacturer’s ripple current ratings are often based on
only 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 also be paralleled to meet size or height require-
ments in the design. Always consult the manufacturer if
there is any question. An additional 0.1 μ F to 1 μ F ceramic
decoupling capacitor is also required on V IN (Pin 1) for
high frequency decoupling.
The selection of C OUT is driven by the required effective
series resistance (ESR). The ESR of C OUT must be less
than twice the value of R SENSE for proper operation of the
LTC1147:
C OUT Required ESR < 2R SENSE
sn1147 1147fds
9
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| LTC1147HVCS8-3.3 | 功能描述:IC REG CTRLR BUCK PWM CM 8-SOIC 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) |
| LTC1147HVCS8-3.3#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 8-SOIC 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:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 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:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
| LTC1147HVCS8-3.3#TR | 功能描述:IC REG CTRLR BUCK PWM CM 8-SOIC 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) |
| LTC1147HVCS8-3.3#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 8-SOIC 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:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 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:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
| LTC1147I | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Efficiency Step-Down Switching Regulator Controllers |
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