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参数资料
| 型号： | LTC1148CS |
| 厂商： | Linear Technology |
| 文件页数： | 8/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 14-SOIC |
| 标准包装： | 55 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 250kHz |
| 占空比： | 100% |
| 电源电压： | 3.5 V ~ 18 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： | 14-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
LTC1148
LTC1148-3.3/LTC1148-5
APPLICATIO S I FOR ATIO
The basic LTC1148 series application circuit (fixed
output versions) is shown in Figure 1. External compo-
nent 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
MOSFETs 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 20V. If the application requires
0.20
0.15
0.10
0.05
higher input voltage, then the LTC1149 or LTC1159
should be used.
0
0
1 2 3 4
MAXIMUM OUTPUT CURRENT (A)
5
R SENSE Selection for Output Current
R SENSE is chosen based on the required output current.
The LTC1148 series current comparator has a threshold
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 LTC1148 series and
external component values yields:
R SENSE = 100mV
I MAX
A graph for selecting R SENSE versus maximum output
LTC1148 ? F02
Figure 2. Selecting R SENSE
The LTC1148 series automatically extends 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 LTC1148 series uses 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 proportional
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, f:
current is given in Figure 2.
The load current below which Burst Mode operation com-
C T =
1
2.6(10 4 )f
mences (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
Assumes V IN = 2V OUT , Figure 1 circuit.
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 be higher, reducing efficiency (see Efficiency
Considerations). The complete expression for operating
frequency of the circuit in Figure 1 is given by:
114835fd
8
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| VI-B2Z-EY-F1 | CONVERTER MOD DC/DC 2V 20W |
| LTC1148CS-5 | IC REG CTRLR BUCK PWM CM 14-SOIC |
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| LTC1148CS-3.3#PBF | IC REG CTRLR BUCK PWM CM 14-SOIC |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1148CS#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:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 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:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC1148CS#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 |
| LTC1148CS#TRPBF | 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:4,500 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 |
| LTC1148CS-3.3 | 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 |
| LTC1148CS-3.3#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:4,500 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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