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| 型号： | LTC1147CS8-5#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 7/16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
The basic LTC1147 application circuit is shown in Figure
1. External component selection is driven by the load
requirement and begins with the selection of R SENSE . Once
R SENSE is known, C T and L can be chosen. Next, the power
MOSFET and D1 are selected. Finally, C IN and C OUT are
selected and the loop is compensated. The circuit shown
in Figure 1 can be configured for operation up to an input
voltage of 16V. If the application requires higher input
voltage, then the synchronous switched LTC1149 should
0.20
0.15
0.10
0.05
be used. Consult factory for lower minimum input voltage
version.
0
0
1 2 3 4
MAXIMUM OUTPUT CURRENT (A)
5
) )
1 V IN – V OUT
C T =
R SENSE Selection for Output Current
R SENSE is chosen based on the required output current.
The LTC1147 series current comparator has a thresh-
old range which extends from a minimum of 25mV/
R SENSE to a maximum of 150mV/R SENSE . The current
comparator threshold sets the peak of the inductor
ripple current, yielding a maximum output current I MAX
equal to the peak value less half the peak-to-peak ripple
current. For proper Burst Mode operation, I RIPPLE(P-P)
must be less than or equal to the minimum current
comparator threshold.
Since efficiency generally increases with ripple current,
the maximum allowable ripple current is assumed, i.e.,
I RIPPLE(P-P) = 25mV/R SENSE (see C T and L Selection for
Operating Frequency). Solving for R SENSE and allowing
a margin for variations in the LTC1147 series and
external component values yields:
R SENSE = 100mV
I MAX
A graph for selecting R SENSE versus maximum output
current is given in Figure 2.
The load current below in which Burst Mode operation
commences, I BURST and the peak short-circuit current
I SC(PK) , both track I MAX . Once R SENSE has been chosen,
I BURST and I SC(PK) can be predicted from the following:
I BURST ≈ 15mV
R SENSE
I SC(PK) = 150mV
R SENSE
LTC1147 ? F02
Figure 2. Selecting R SENSE
The LTC1147 series automatically extend t OFF during a
short circuit to allow sufficient time for the inductor
current to decay between switch cycles. The resulting
ripple current causes the average short-circuit current
I SC(AVG) to be reduced to approximately I MAX .
L and C T Selection for Operating Frequency
The LTC1147 series use a constant off-time architecture
with t OFF determined by an external timing capacitor C T .
Each time the P-channel MOSFET switch turns on, the
voltage on C T is reset to approximately 3.3V. During the
off-time, C T is discharged by a current which is propor-
tional to V OUT . The voltage on C T is analogous to the
current in inductor L, which likewise decays at a rate
proportional to V OUT . Thus the inductor value must track
the timing capacitor value.
The value of C T is calculated from the desired continuous
mode operating frequency:
(1.3)(10 4 )(f) V IN + V D
Where V D is the drop across the Schottky diode.
A graph for selecting C T versus frequency including the
effects of input voltage is given in Figure 3.
As the operating frequency is increased the gate charge
losses will reduce efficiency (see Efficiency Consider-
ations). The complete expression for operating frequency
sn1147 1147fds
7
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相关代理商/技术参数 |
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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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