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参数资料
| 型号： | LTC3811EUHF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 22/48页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 38-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 850kHz |
| 占空比： | 90% |
| 电源电压： | 4.5 V ~ 30 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： | 38-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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LTC3811
OPERATION
(Refer to the Functional Diagram)
I LIMIT =
? Δ I L
R SENSE
Δ I L(SC) = t ON(MIN) ?
PGOODoutputsfortheunusederrorampli?ersshouldbe
left open. Only the PGOOD output for the master control
error ampli?er should be connected to the fault monitor.
Fault Conditions: Current Limit and Foldback
One of the main advantages of the LTC3811 is the fact that
the maximum inductor current is inherently limited due
to the use of peak current mode control. The maximum
sense voltage is controlled by the voltage on the RNG pins
and the maximum DC output current is:
V SENSE(MAX) 1
–
2
Under short-circuit conditions with very low duty cycles,
the LTC3811 may begin to skip pulses in order to limit the
maximum current. In this situation the bottom MOSFET
will be dissipating most of the power; however this will
be less than in normal operation at maximum load. In this
case the short circuit ripple current is determined by the
minimum on-time, t ON(MIN) , of the LTC3811 (about 65ns),
the input voltage, and the inductor value, according to the
following equation:
V IN
L
The resulting short-circuit current is
The current limit value should be checked to ensure that
I LIMIT(MIN) > I OUT(MAX) . The minimum value of the current
I SC =
0.3 ? V SENSE(MAX)
R SENSE
–
1
2
? Δ I L(SC)
I SC = = t ON(MIN) ?
limit generally occurs with the largest V IN at the highest
ambient temperature, conditions that cause the largest
power losses in the converter.
To further limit current in the event of an output short-circuit
to ground, the LTC3811 includes foldback current limiting.
When the FB pin falls below 0.3V (50% of its nominally
regulated value), the foldback circuit is activated, progres-
sively lowering the peak current limit in proportion to the
severity of the overcurrent or short circuit condition. If the
FB pin reaches 0V, the peak current sense threshold will
be reduced to 30% of its maximum value. The foldback
current limit transfer function is shown in Figure 8.
60
55
50
45
40
35
30
25
20
15
Depending upon the ratio of the DC value of the current
limit to the maximum load current and the percentage
ripple current in the inductor, it is possible that the con-
verter will operate in discontinuous mode when V FB = 0V
(a so-called “dead short”). In this case, the short-circuit
current of the converter will be:
Δ I L(SC) V IN
2 2?L
In order for the converter to start up properly with a non-
linear load, the foldback current limiting circuit in the
LTC3811 is disabled during the initial soft-start interval.
When the FB pin voltage reaches 0.54V, the soft-start in-
terval is terminated and the foldback circuit is enabled.
In the event the converter is turned on into a shorted load,
the foldback circuit will be disabled until the SS/TRACK
pin reaches 0.54V. This ensures that the converter will still
limit the maximum current to a safe level and reduce the
peak power dissipated with a shorted load.
10
5
RNG = INTV CC
0
0
100
200 300 400
500
600
700
FB VOLTAGE (mV)
3811 G31
Figure 8. Current Foldback Charactistic
3811f
22
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3812EFE5#PBF | 制造商:Linear Technology 功能描述: |
| LTC3812EFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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 |
| LTC3812EFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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) |
| LTC3812IFE-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP 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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