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参数资料
| 型号： | LTC1772BIS6#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO6 |
| 封装： | LEAD FREE, PLASTIC, MO-193, SOT-23, 6 PIN |
| 文件页数： | 16/16页 |
| 文件大小： | 223K |
| 代理商： | LTC1772BIS6#PBF |
LTC1772B
9
1772bfa
APPLICATIONS INFORMATION
Since the LTC1772B is designed for operation down to low
input voltages, a logic level threshold MOSFET (RDS(ON)
guaranteed at VGS = 2.5V) is required for applications that
work close to this voltage. When these MOSFETs are used,
make sure that the input supply to the LTC1772B is less
than the absolute maximum VGS rating, typically 8V.
The required minimum RDS(ON) of the MOSFET is governed
by its allowable power dissipation. For applications that
may operate the LTC1772B in dropout, i.e., 100% duty
cycle, at its worst case the required RDS(ON) is given by:
RDS(ON)
DC=100%
=
PP
IOUT(MAX)
()
2
1+ p
(
)
where PP is the allowable power dissipation and δp is the
temperature dependency of RDS(ON). (1 + δp) is generally
given for a MOSFET in the form of a normalized RDS(ON)
vs temperature curve, but δp = 0.005/°C can be used as
an approximation for low voltage MOSFETs.
In applications where the maximum duty cycle is less
than 100% and the LTC1772B is in continuous mode, the
RDS(ON) is governed by:
RDS(ON)
PP
DC
()IOUT
2 1+ p
(
)
where DC is the maximum operating duty cycle of the
LTC1772B.
Output Diode Selection
The catch diode carries load current during the off-time.
The average diode current is therefore dependent on the
P-channel switch duty cycle. At high input voltages the
diode conducts most of the time. As VIN approaches VOUT
the diode conducts only a small fraction of the time. The
most stressful condition for the diode is when the output
is short-circuited. Under this condition the diode must
safely handle IPEAK at close to 100% duty cycle. Therefore,
it is important to adequately specify the diode peak cur-
rent and average power dissipation so as not to exceed
the diode ratings.
Under normal load conditions, the average current con-
ducted by the diode is:
ID =
VIN VOUT
VIN+ VD
IOUT
The allowable forward voltage drop in the diode is calculated
from the maximum short-circuit current as:
V
P
I
F
D
SC MAX
≈
()
where PD is the allowable power dissipation and will be
determined by efciency and/or thermal requirements.
A fast switching diode must also be used to optimize
efciency. Schottky diodes are a good choice for low
forward drop and fast switching times. Remember to
keep lead length short and observe proper grounding (see
Board Layout Checklist) to avoid ringing and increased
dissipation.
CIN and COUT Selection
In continuous mode, the source current of the P-chan-
nel MOSFET is a square wave of duty cycle (VOUT + VD)/
(VIN + VD). 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:
CI
VV
V
IN
MAX
OUT
IN
OUT
IN
Required IRMS ≈
()
[]
12
/
This formula has a maximum value at VIN = 2VOUT, where
IRMS = IOUT/2. This simple worst-case condition is com-
monly used for design because even signicant 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
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相关代理商/技术参数 |
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| LTC1772CS6 | 制造商:Linear Technology 功能描述:Swithed-Mode Power Supply Controller, Current Mode Type, 3 Pin, Plastic, TO-236 |
| LTC1772CS6#PBF | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.5V to 9.8V Input 6-Pin TSOT-23 制造商:Linear Technology 功能描述:BUCK 2.8 - 20V 5A 1.23-18V 6SOT23 制造商:Linear Technology 功能描述:BUCK, 2.8 - 20V, 5A, 1.23-18V, 6SOT23 |
| LTC1772CS6#TR | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 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) |
| LTC1772CS6#TRM | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 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) |
| LTC1772CS6#TRMPBF | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 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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