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参数资料
| 型号： | LT3474IFE-1#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 9/20页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR HP CONS CURR 16TSSOP |
| 标准包装： | 2,500 |
| 恒定电流： | 是 |
| 拓扑： | PWM，降压（降压） |
| 输出数： | 1 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 车载，背光 |
| 类型 - 次要： | 颜色，白色 LED |
| 频率： | 200kHz ~ 2MHz |
| 电源电压： | 3.5 V ~ 36 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 供应商设备封装： | 16-TSSOP-EP |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 125°C |
LT3474/LT3474-1
APPLICATIONS INFORMATION
The switch driver operates either from V IN or from the
BOOST pin. An external capacitor and internal Schottky
diode are used to generate a voltage at the BOOST pin
that is higher than the input supply. This allows the driver
to saturate the internal bipolar NPN power switch for ef-
?cient operation.
Open Circuit Protection
An internal comparator will force the part into shutdown
when V IN falls below 3.5V. If an adjustable UVLO threshold
is required, the SHDN pin can be used. The threshold
voltage of the SHDN pin comparator is 2.65V. A internal
resistor pulls 10.3μA to ground from the SHDN pin at the
UVLO threshold.
Choose resistors according to the following formula:
V TH – 2.65V
TheLT3474hasinternalopencircuitprotection.IftheLEDis
absent or fails open, the LT3474 clamps the voltage on the
LED pin at 14V. The switching regulator then skips cycles
R2 =
R1
2.65V
– 10.3 μ A
to limit the input current. The LT3474-1 has no internal
open circuit protection. With the LT3474-1, be careful not
to violate the ABSMAX voltage of the BOOST pin; if V IN >
25V, external open circuit protection circuitry (as shown in
Figure 2) may be necessary. The output voltage during an
open LED condition is shown in the Typical Performance
Characteristics section.
V TH = UVLO Threshold
Example: Switching should not start until the input is
above 8V.
V TH = 8V
R1 = 100k
Undervoltage Lockout
Undervoltage lockout (UVLO) is typically used in situations
where the input supply is current limited, or has high source
R2 =
2.65V
8V – 2.65V
– 10.3 μ A
100k
= 61.9k
resistance. A switching regulator draws constant power
from the source, so the source current increases as the
source voltage drops. This looks like a negative resistance
load to the source and can cause the source to current limit
or latch low under low source voltage conditions. UVLO
Keep the connections from the resistors to the SHDN pin
short and make sure the coupling to the SW and BOOST
pins is minimized. If high resistance values are used, the
SHDN pin should be bypassed with a 1nF capacitor to
prevent coupling problems from switching nodes.
prevents the regulator from operating at source voltages
where these problems might occur.
LT3474
OUT
10k
V IN
R1
V IN
2.65V
V C
SHDN
27V
V C
C1
R2
10.3μA
GND
100k
3474 F03
3474 F02
Figure 2. External Overvoltage Protection
Figure 3. Undervoltage Lockout
Circuitry for the LT3474-1.
3474fd
9
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3474IFE-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Step-Down 1A LED Driver |
| LT3474IFE-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Step-Down 1A LED Driver |
| LT3475 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Step-Down l 1.5A LED Driver |
| LT3475-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Step-Down l 1.5A LED Driver |
| LT3475EFE | 制造商:Linear Technology 功能描述:LED DRVR 2Segment 5V/9V/12V/15V/18V/24V 20-Pin TSSOP EP |
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