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参数资料
| 型号： | LT3477EUF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 7/20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
OPERATION
The LT3477 uses a ?xed frequency, current mode control
scheme to provide excellent line and load regulation. Op-
eration can be best understood by referring to the Block
Diagram in Figure 1. The start of each oscillator cycle sets
the SR latch and turns on power switch Q1. The signal
at the noninverting input of the PWM comparator (A4
SLOPE) is proportional to the sum of the switch current
and oscillator ramp. When SLOPE exceeds V C (the output
of the feedback ampli?er), the PWM comparator resets
the latch and turns off the power switch. In this manner,
the feedback ampli?er and PWM comparators set the
correct peak current level to keep the output in regula-
tion. Ampli?er A3 drives A4 inverting input. A3 has three
inputs, one from the voltage feedback loop and the other
two from the current feedback loop. Whichever feedback
input is higher takes precedence, forcing the converter into
either a constant-current or a constant-voltage mode. The
LT3477 is designed to transition cleanly between the two
modes of operation. Current sense ampli?er IA1 senses
the voltage between the I SP1 and I SN1 pins and provides
a pre-gain to ampli?er A1. When the voltage between I SP1
and I SN1 reaches 100mV, the output of IA1 provides V ADJ
to the inverting input of A1 and the converter is in con-
stant-current mode. If the current sense voltage exceeds
100mV, the output of IA1 will increase causing the output
of A3 to decrease, thus reducing the amount of current
delivered to the output. In this manner the current sense
voltage is regulated to 100mV. The current sense level is
also pin adjustable by I ADJ1 . Forcing I ADJ1 to less than
625mV will overwrite V ADJ voltage that’s set internally,
thus providing current level control. The second current
sense ampli?er, IA2, works the same as the ?rst current
sense ampli?er IA1. Both current sense ampli?ers provide
rail-to-rail current sense operation. Similarly, for positive
output voltage operation where FBP is tied to V REF , if
the FBN pin increases above V REF , the output of A3 will
decrease to reduce the peak current level and regulate
the output (constant-voltage mode). For negative output
voltage operation where FBN is tied to GND, if the FBP pin
decreases below GND level, the output of A3 will decrease
to reduce the peak current level and regulate the output
(constant-voltage mode).
The LT3477 also features a soft-start function. During
start-up, 9μA of current charges the external soft-start
capacitor. The SS pin directly limits the rate of voltage rise
on the V C pin, which in turn limits the peak switch cur-
rent. The switch current is constantly monitored and not
allowed to exceed the nominal value of 3A. If the switch
current reaches 3A, the SR latch is reset regardless of the
output of the PWM comparator. Current limit protects the
power switch and external components.
3477fc
7
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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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