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参数资料
| 型号： | LT3477EUF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 9/20页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR HP CONST CURR 20-QFN |
| 标准包装： | 2,500 |
| 恒定电流： | 是 |
| 恒定电压： | 是 |
| 拓扑： | 回扫，PWM，SEPIC，降压（降压），升压（升压） |
| 输出数： | 1 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 通用 |
| 类型 - 次要： | 白色 LED |
| 频率： | 200kHz ~ 3.5MHz |
| 电源电压： | 2.5 V ~ 25 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-WFQFN 裸露焊盘 |
| 供应商设备封装： | 20-QFN 裸露焊盘（4x4） |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 85°C |
LT3477
APPLICATIONS INFORMATION
V OUT = 1.235V 1 +
Setting Positive Output Voltages
To set a positive output voltage, select the values of R1 and
R2 (see Figure 2) according to the following equation:
R1
R2
FBP
For designs needing an adjustable current level, the
I ADJ1 and I ADJ2 pins are provided for the ?rst and the
second current sense ampli?ers, respectively. With the
I ADJ1 and I ADJ2 pins tied higher than 650mV, the nominal
current sense voltage is 100mV (appearing between the
I SP1 and I SN2 or I SP2 and I SN2 pins). Applying a positive
DC voltage less than 600mV to the I ADJ1 and I ADJ2 pins
will decrease the current sense voltage according to the
LT3477
V OUT
following formula:
V REF
FBN
R1
R2
I SENSE =
100mV V IADJ
?
R SENSE 618 mV
3477 F02
Figure 2. Positive Output Voltage Feedback Connections
Setting Negative Output Voltages
To set a negative output voltage, select the values of R3 and
R4 (see Figure 3) according to the following equation:
For example, if 309mV is applied to the I ADJ1 pin and
R SENSE is 0.5Ω, the current sense will be reduced from
200mA to 100mA. The adjustability allows the regulated
current to be reduced without changing the current sense
resistor (e.g., to adjust brightness in an LED driver or to
reduce the charge current in a battery charger).
Considerations When Sensing Input Current
V OUT = –1.235V
R3
R4
–V OUT
R3
In addition to regulating the DC output current for cur-
rent-source applications, the constant-current loop of
the LT3477 can also be used to provide an accurate input
current limit. Boost converters cannot provide output
short-circuit protection, but the surge turn-on current can
LT3477
FBP
V REF
R4
be drastically reduced using the LT3477 current sense at
the input. SEPICs, however, have an output that is DC-
isolated from the input, so an input current limit not only
FBN
3477 F03
Figure 3. Negative Output Voltage Feedback Connections
Selecting R SENSE /Current Sense Adjustment
Using the following formula to choose the correct current
sense resistor value (for constant current or fail-safe
operation).
helps soft-start the output but also provides excellent
short-circuit protection.
When sensing input current, the sense resistor should be
placed in front of the inductor (between the decoupling
capacitor and the inductor). This will regulate the average
inductor current and maintain a consistent inductor ripple
current, which will, in turn, maintain a well regulated input
current. Do not place the sense resistor between the input
source and the input decoupling capacitor, as this may allow
R SENSE =
100mV
I SENSE
the inductor ripple current to vary widely (even though the
average input current and the average inductor current will
still be regulated). Since the inductor current is a triangular
waveform (not a DC waveform like the output current)
3477fc
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3477IFE | 制造商:LINER 制造商全称:Linear Technology 功能描述:3A, DC/DC Converter with Dual Rail-to-Rail Current Sense |
| LT3477IFE#PBF | 功能描述:IC LED DRVR HP CONS CURR 20TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
| LT3477IFE#TRPBF | 功能描述:IC LED DRVR HP CONS CURR 20TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
| LT3477IUF | 制造商:LINER 制造商全称:Linear Technology 功能描述:3A, DC/DC Converter with Dual Rail-to-Rail Current Sense |
| LT3477IUF#PBF | 功能描述:IC LED DRVR HP CONST CURR 20-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:60 系列:- 恒定电流:- 恒定电压:- 拓扑:线性（LDO），PWM，升压（升压） 输出数:8 内部驱动器:是 类型 - 主要:背光 类型 - 次要:RGB，白色 LED 频率:500kHz ~ 1.5MHz 电源电压:4.75 V ~ 26 V 输出电压:45V 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* 工作温度:-40°C ~ 85°C |
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