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参数资料
| 型号： | LTC3454EDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/12页 |
| 文件大小： | 0K |
| 描述： | IC LED DRIVER PHOTO FLASH 10-DFN |
| 标准包装： | 2,500 |
| 拓扑： | PWM，降压（降压），升压（升压） |
| 输出数： | 1 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光，闪灯/白光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 900kHz ~ 1.15MHz |
| 电源电压： | 2.7 V ~ 5.5 V |
| 输出电压： | 5.15V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-WFDFN 裸露焊盘 |
| 供应商设备封装： | 10-DFN（3x3） |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 85°C |
LTC3454
TYPICAL APPLICATIONS
diode such as an MBRM120T3 or equivalent. Do not use
ordinary recti?er diodes, since the slow recovery times
will compromise ef?ciency.
In applications in which V IN is greater than 4V and V OUT to
GND short-circuit protection is needed, a Schottky diode
and slower transient response. To ensure proper phase
margin, the loop is required to be crossed over a decade
before the LC double pole.
The unity-gain frequency of the error ampli?er with the
Type I compensation is given by:
such as MBRM120T3 or equivalent may be used from
GND to SW1 and/or a 2 Ω /1nF series snubber from SW1
to GND. The Schottky diode should be added as close
f UG =
g m
2 ? π ? C VC
to the pins as possible. Neither of these is required for
shorted LED protection.
In applications in which V IN is greater than 4.5V, a Schottky
diode such as MBRM120T3 or equivalent may be required
from SW1 to V IN if the LTC3454 is enabled with an output
voltage already present. The Schottky diode should be
added as close to the pins as possible.
Closing the Feedback Loop
The LTC3454 incorporates voltage mode PWM control.
The control to output gain varies with operation region
(buck, boost, buck/boost), but is usually no greater than
15. The output ?lter exhibits a double pole response
where g m is the error amp transconductance (typically
1/5.2k) and C VC is the external capacitor to GND at the
V C pin. For the white LED application, a 0.1μF or greater
capacitor value is recommended.
Maximum LED Current
As described in the Operation section, the output LED
current with both enable pins logic high is equal to
I LED = 3850 [0.8V/(R ISET1 || R ISET2 )]
Since the maximum continuous output current is limited to
1A, this sets a minimum limit on the parallel combination
of R ISET1 and R ISET2 equal to
given by:
f FILTER _ POLE =
1
2 ? π ? L ? C OUT
Hz
R MIN = (R ISET1 || R ISET2 )| MIN = 3850(0.8V/1A)
= 3080 Ω
Although the LTC3454 can safely provide this current
where C OUT is the output ?lter capacitor.
The output ?lter zero is given by:
continuously, the external LED may not be rated for this
high a level of continuous current. Higher current levels
are generally reserved for pulsed applications, such as
f FILTER _ ZERO =
1
2 ? π ? R ESR ? C OUT
Hz
LED camera ?ash. This is accomplished by programming
a high current with one of the R ISET resistors and pulsing
the appropriate enable pin.
=
V IN
2 ? π ? I OUT OUT
whereR ESR isthecapacitorequivalentseriesresistance.
A troublesome feature in boost mode is the right-half plane
zero (RHP), and is given by:
2
f RHPZ Hz
? L ? V
The loop gain is typically rolled off before the RHP zero
frequency.
A simple Type I compensation network can be incorporated
Varying LED Brightness
Continuously variable LED brightness control can be
achieved by interfacing directly to one or both of the I SET
pins. Figure 3 shows four such methods employing a
voltage DAC, a current DAC, a simple potentiometer or a
PWM input. It is not recommended to control brightness
by PWMing the enable pins directly as this will toggle
the LTC3454 in and out of shutdown and result in erratic
operation.
to stabilize the loop but at a cost of reduced bandwidth
3454fa
10
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相关代理商/技术参数 |
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| LTC3455 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Efficiency Battery Charger/USB Power Manager |
| LTC3455EUF | 功能描述:IC CONV DC/DC DUAL USBBATT 24QFN RoHS:否 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP（4x4） 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR |
| LTC3455EUF#PBF | 功能描述:IC CONV DC/DC DUAL USBBATT 24QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP（4x4） 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR |
| LTC3455EUF#TR | 功能描述:IC CONV DC/DC DUAL USBBATT 24QFN RoHS:否 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP（4x4） 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR |
| LTC3455EUF#TRPBF | 功能描述:IC CONV DC/DC DUAL USBBATT 24QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP（4x4） 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR |
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