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参数资料
| 型号： | LTC1148HVCS-3.3#TR |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 250 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封装： | 0.150 INCH, PLASTIC, SOP-14 |
| 文件页数： | 2/20页 |
| 文件大小： | 237K |
| 代理商： | LTC1148HVCS-3.3#TR |
10
LTC1148
LTC1148-3.3/LTC1148-5
114835fd
APPLICATIO S I FOR ATIO
W
UU
U
level threshold MOSFETs (VGS(TH) < 2.5V) are strongly
recommended. The LTC1148/LTC1148HV series supply
voltage must always be less than the absolute maximum
VGS ratings for the MOSFETs.
The maximum output current IMAX determines the RDS(ON)
requirement for the two MOSFETs. When the LTC1148
series is operating in continuous mode, the simplifying
assumption can be made that one of the two MOSFETs is
always conducting the average load current. The duty
cycles for the two MOSFETs are given by:
P-Ch Duty Cycle =
VOUT
VIN
N-Ch Duty Cycle =
(VIN – VOUT)
VIN
From the duty cycles the required RDS(ON) for each MOS-
FET can be derived:
P-Ch RDS(ON) =
VIN(PP)
VOUT(IMAX2)(1 + δP)
N-Ch RDS(ON) =
VIN(PN)
(VIN – VOUT)(IMAX2)(1 + δN)
where PP and PN are the allowable power dissipations and
dP and dN are the temperature dependencies of RDS(ON).
PP and PN will be determined by efficiency and/or thermal
requirements (see Efficiency Considerations). (1 + d) is
generally given for a MOSFET in the form of a normalized
RDS(ON) vs temperature curve, but d = 0.007/°C can be
used as an approximation for low voltage MOSFETs.
The Schottky diode D1 shown in Figure 1 only conducts
during the dead-time between the conduction of the two
power MOSFETs. D1’s sole purpose in life is to prevent the
body diode of the N-channel MOSFET from turning on and
storing charge during the dead time, which could cost as
much as 1% in efficiency (although there are no other
harmful effects if D1 is omitted). Therefore, D1 should be
selected for a forward voltage of less than 0.7V when
conducting IMAX.
CIN and COUT Selection
In continuous mode, the source of the P-channel MOSFET
is a square wave of duty cycle VOUT/VIN. 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:
CIN Required IRMS ≈ IMAX
[VOUT(VIN – VOUT)]1/2
VIN
This formula has a maximum at VIN = 2VOUT, where
IRMS = IOUT/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. Always consult the
manufacturer if there is any question. An additional 0.1F
to 1F ceramic capacitor is also required on VIN Pin 3 for
high frequency decoupling.
The selection of COUT is driven by the required effective
series resistance (ESR).
The ESR of COUT must be less
than twice the value of RSENSE for proper operation of the
LTC1148 series:
COUT Required ESR < 2RSENSE
Optimum efficiency is obtained by making the ESR equal
to RSENSE. As the ESR is increased up to 2RSENSE, the
efficiency degrades by less than 1%. If the ESR is greater
than 2RSENSE, the voltage ripple on the output capacitor
will prematurely trigger Burst Modeoperation, resulting in
disruption of continuous mode and an efficiency hit which
can be several percent.
Manufacturers such as Nichicon and United Chemicon
should be considered for high performance capacitors.
The OS-CON semiconductor dielectric capacitor available
from Sanyo has the lowest ESR/size ratio of any aluminum
electrolytic at a somewhat higher price. Once the ESR
requirement for COUT has been met, the RMS current
rating generally far exceeds the IRIPPLE(P-P) requirement.
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| LTC1148HVCS5 | 制造商:LT 功能描述:REREALED |
| LTC1148HVCS-5 | 功能描述:IC REG CTRLR BUCK PWM CM 14-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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1148HVCS-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 14-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) |
| LTC1148HVCS-5#TR | 功能描述:IC REG CTRLR BUCK PWM CM 14-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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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