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| 型号： | LTC1266CS-3.3 |
| 厂商： | Linear Technology |
| 文件页数： | 9/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 16-SOIC |
| 标准包装： | 50 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 400kHz |
| 占空比： | 100% |
| 电源电压： | 3.5 V ~ 18 V |
| 降压： | 是 |
| 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： | 0°C ~ 70°C |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1342 (CN2011-ZH PDF) |
LTC1266
LTC1266-3.3/LTC1266-5
APPLICATIO S I FOR ATIO
R SENSE Selection for Output Current
R SENSE is chosen based on the required output current.
The LTC1266 series current comparator has a threshold
range which extends from a minimum of 25mV/R SENSE
(when Burst Mode operation is enabled) to a maximum of
155mV/R SENSE . The current comparator threshold sets
the peak of the inductor ripple current, yielding a maxi-
mum 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 LTC1266 series and
external component values yields:
R SENSE = 100mV
I MAX
A graph for selecting R SENSE vs maximum output
current is given in Figure 2.
100
I BURST ≈ 15mV
R SENSE
I SC(PK) = 155mV
R SENSE
The LTC1266 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 LTC1266 series uses a constant off-time architecture
with t OFF determined by an external timing capacitor C T .
Each time the topside 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, f:
75
C T =
1
2.6 ? 10 4 ? f
assumes V IN = 2V OUT , (Figure 1 circuit).
50
A graph for selecting C T vs frequency including the effects
of input voltage is given in Figure 3.
25
800
V OUT = 3.3V
0
0
2
4
6
8
10
600
MAXIMUM OUTPUT CURRENT (A)
1266 F02
Figure 2. Selecting R SENSE
The load current, below which Burst Mode operation
commences, (I BURST ), and the peak short-circuit cur-
400
200
V IN = 5V
V IN = 12V
rent, (I SC(PK) ), both track I MAX . Once R SENSE has been
chosen, I BURST and I SC(PK) can be predicted from the
0
0
100
200 300
400
500
following:
FREQUENCY (kHz)
1266 F03
Figure 3. Timing Capacitor Value
9
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1266CS-5 | 功能描述:IC REG CTRLR BST PWM CM 16-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) |
| LTC1266CS-5#PBF | 功能描述:IC REG CTRLR BST PWM CM 16-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: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) |
| LTC1266CS-5#TR | 功能描述:IC REG CTRLR BST PWM CM 16-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) |
| LTC1266CS-5#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 16-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) |
| LTC1266IS | 功能描述:IC REG CTRLR BST PWM CM 16-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) |
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