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参数资料
| 型号： | LTC1147CS8-5#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/16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
1000
800
600
400
V SENSE – = V OUT = 5V
V IN = 12V
series will delay entering Burst Mode operation and effi-
ciency will be degraded at low currents.
Inductor Core Selection
Once the minimum value for L is known, the type of
inductor must be selected. Highest efficiency will be
obtained using ferrite, Kool M μ ? (from Magnetics, Inc.) or
200
V IN = 7V
V IN = 10V
molypermalloy (MPP) cores. Lower cost powdered iron
cores provide suitable performance but cut efficiency by
0
0
100
200
300
3% to 5%. Actual core loss is independent of core size for
FREQUENCY (kHz)
LTC1147 ? F03
Figure 3. Timing Capacitor Value
a fixed inductor value, but it is very dependent on induc-
tance selected. As inductance increases, core losses go
down. Unfortunately, increased inductance requires more
turns of wire and therefore copper losses will increase.
f ≈
)
is given by:
1
t OFF
1–
V OUT
V IN
)
Ferrite designs have very low core loss, so design goals
can concentrate on copper loss and preventing satura-
tion. Ferrite core material saturates “hard,” which means
that inductance collapses abruptly when the peak design
) )
t OFF = (1.3)(10 4 )(C T ) REG
where:
V
V OUT
V REG is the desired output voltage (i.e., 5V, 3.3V). V OUT is
the measured output voltage. Thus V REG /V OUT = 1 in
regulation.
Note that as V IN decreases, the frequency decreases.
When the input to output voltage differential drops
below 1.5V, the LTC1147 reduces t OFF by increasing the
discharge current in C T . This prevents audible opera-
tion prior to dropout.
Once the frequency has been set by C T , the inductor L
must be chosen to provide no more than 25mV/R SENSE
of peak-to-peak inductor ripple current. This results in
a minimum required inductor value of:
L MIN = (5.1)(10 5 )(R SENSE )(C T )(V REG )
As the inductor value is increased from the minimum
value, the ESR requirements for the output capacitor
are eased at the expense of efficiency. If too small an
inductor is used, the inductor current will become
discontinuous before the LTC1147 series enters Burst
Mode operation. A consequence of this is that the LTC1147
current is exceeded. This results in an abrupt increase in
inductor ripple current and consequent output voltage
ripple which can cause Burst Mode operation to be
falsely triggered in the LTC1147. Do not allow the core
to saturate!
Kool M μ is a very good, low loss core material for toroids
with a “soft” saturation characteristic. Molypermalloy is
slightly more efficient at high (>200kHz) switching fre-
quencies but quite a bit more expensive. Toroids are very
space efficient, especially when you can use several
layers of wire. Because they generally lack a bobbin,
mounting is more difficult. However, new designs for
surface mount are available from Coiltronics, Sumida and
Beckman Industrial Corp. which do not increase the
height significantly.
Power MOSFET Selection
An external P-channel power MOSFET must be selected
for use with the LTC1147 series. The main selection
criteria for the power MOSFET are the threshold voltage
V GS(TH) and “on” resistance R DS(ON) .
The minimum input voltage determines whether a stan-
dard threshold or logic-level threshold MOSFET must be
Kool M μ is a registered trademark of Magnetics, Inc.
sn1147 1147fds
8
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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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