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参数资料
| 型号： | LT3799IMSE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/20页 |
| 文件大小： | 0K |
| 描述： | IC LED DRIVER TRIAC DIM 16-MSOP |
| 产品培训模块： | LT3799 Offline Isolated Flyback LED Controller |
| 标准包装： | 37 |
| 拓扑： | 交直流离线开关，反激式，PFC |
| 输出数： | 1 |
| 内部驱动器： | 无 |
| 类型 - 主要： | 通用 |
| 频率： | 25kHz ~ 300kHz |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TFSOP（0.118"，3.00mm 宽）裸露焊盘 |
| 供应商设备封装： | 16-MSOP，裸露焊盘 |
| 包装： | 管件 |
| 工作温度： | -40°C ~ 125°C |
| 配用： | 732-2898-ND - IND TOROID LT3799 NCL30000 750UH |
LT3799
OPERATION
V OUT ? N
V OUT ? N + V IN
I OUT = CTRL ?
R1 = R2 ?
? 1 ?
I OUT(MAX) = 2 ? (1 ? D) ?
V OUT ? N
V OUT ? N + V IN
= 2 ? (1 ? D) ?
I OUT(MAX)
? 47.5%
I OUT = CTRL ?
R1 = R2 ?
? 1 ?
beginstoswitch.Theoutputvoltageinformationfromthe
FB pin is sampled but ignored until the CT pin reaches
1.25V. When this occurs, if the FB pin is above 1.25V, the
fault flag pulls low. The FAULT pin is meant to be used
with a large pull-up resistor to the INTV CC pin or another
supply. The CT pin begins to sink 200nA of current. When
the CT pin goes below 240mV, the part will re-enable itself,
begin to switch, and start to source 10μA of current to the
CT pin but not remove the fault condition. When the CT
pin reaches 1.25V and FB is below 1.25V, the FAULT pin
will no longer pull low and switching will continue. If not
below 1.25V, the process repeats itself.
Programming Output Current
The maximum output current depends on the supply
voltage and the output voltage in a flyback topology.
With the V IN_SENSE pin connected to 1V and a DC supply
voltage, the maximum output current is determined at
the minimum supply voltage, and the maximum output
voltage using the following equation:
N
42 ? R SENSE
where
D =
The maximum control voltage to achieve this maximum
output current is 2V ? (1-D).
It is suggested to operate at 95% of these values to give
margin for the part’s tolerances.
When designing for power factor correction, the output
current waveform is going to have a half sine wave squared
shape and will no longer be able to provide the above
currents. By taking the integral of a sine wave squared
over half a cycle, the average output current is found to
be half the value of the peak output current. In this case,
the recommended maximum average output current is
as follows:
N
42 ? R SENSE
where
D =
The maximum control voltage to achieve this maximum
output current is (1-D) ? 47.5%.
For control voltages below the maximum, the output cur-
rent is equal to the following equation:
N
42 ? R SENSE
The V REF pin supplies a 2V reference voltage to be used
with the control pins. To set an output current, a resistor
divider is used from the 2V reference to one of the control
pins. The following equation sets the output current with
a resistor divider:
? 2N ?
? 42 ? I OUT ? R SENSE ?
where R1 is the resistor connected to the V REF pin and the
CTRL pin and R2 is the resistor connected to the CTRL
pin and ground.
When used with an AC input voltage, the LT3799 senses
when the V IN_SENSE goes below 65mV and above 65mV
for detecting when the TRIAC is off. During this low input
voltage time, the output current regulation loop is off but the
part still switches. This helps with output current regulation
with a TRIAC but introduces a line regulation error. When
V IN_SENSE is low, very little power is being delivered to the
output and since the output current regulation loop is off,
this time period needs to be accounted for in setting the
output current. This time period slightly varies with line
voltage. Figure 2 shows the correction factor in selecting
the resistor divider resistors. When used with AC, the fol-
lowing equation should be used with the correction factor:
N
42 ? R SENSE ? CF
? 2N ?
? 42 ? I OUT ? R SENSE ? CF ?
3799fa
11
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| LT3800EFE#PBF | 功能描述:IC REG CTRLR INV PWM CM 16-TSSOP 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 |
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