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| 型号： | LT3755IMSE-2#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/26页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR HP CONS CURR 16-MSOP |
| 标准包装： | 2,500 |
| 恒定电流： | 是 |
| 恒定电压： | 是 |
| 拓扑： | 回扫，低端，PWM，SEPIC，降压（降压），升压（升压） |
| 输出数： | 1 |
| 内部驱动器： | 无 |
| 类型 - 主要： | 车载 |
| 类型 - 次要： | 白色 LED |
| 频率： | 100kHz ~ 1MHz |
| 电源电压： | 4.5 V ~ 40 V |
| 输出电压： | 75V |
| 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： | 带卷 (TR) |
| 工作温度： | -40°C ~ 125°C |
LT3755/LT3755-1/LT3755-2
APPLICATIONS INFORMATION
C IN (μF) = I LED (A) ? t SW (μs) ? 4.7 ? ?
T SS = C SS ?
Therefore, a 10μF capacitor is an appropriate selection
for a 400kHz boost regulator with 12V input, 48V output
and 1A load.
With the same V IN voltage ripple of 100mV, the input capaci-
tor for a buck converter can be estimated as follows:
? μF ?
? A ? μs ? ?
A 10μF input capacitor is an appropriate selection for a
400kHz buck mode converter with a 1A load.
In the buck mode configuration, the input capacitor has
large pulsed currents due to the current returned through
the Schottky diode when the switch is off. In this buck
converter case it is important to place the capacitor as close
as possible to the Schottky diode and to the GND return
of the switch (i.e., the sense resistor). It is also important
to consider the ripple current rating of the capacitor. For
best reliability, this capacitor should have low ESR and
ESL and have an adequate ripple current rating. The RMS
input current for a buck mode LED driver is:
I IN(RMS) = I LED ? ( 1 – D ) ? D
where D is the switch duty cycle.
Table 2. Recommended Ceramic Capacitor Manufacturers
MANUFACTURER WEB
TDK www.tdk.com
Kemet www.kemet.com
Murata www.murata.com
Taiyo Yuden www.t-yuden.com
Output Capacitor Selection
The selection of the output capacitor depends on the load
and converter configuration, i.e., step-up or step-down
and the operating frequency. For LED applications, the
equivalent resistance of the LED is typically low and the
output filter capacitor should be sized to attenuate the
current ripple. Use of X7R type ceramic capacitors is
recommended.
To achieve the same LED ripple current, the required filter
capacitor is larger in the boost and buck-boost mode ap-
plications than that in the buck mode applications. Lower
operating frequencies will require proportionately higher
capacitor values.
Soft-Start Capacitor Selection
For many applications, it is important to minimize the
inrush current at start-up. The built-in soft-start circuit
significantly reduces the start-up current spike and output
voltage overshoot. The soft-start interval is set by the soft-
start capacitor selection according to the equation:
2V
10μA
A typical value for the soft-start capacitor is 0.01μF. The
soft-start pin reduces the oscillator frequency and the
maximum current in the switch. The soft-start capacitor
is discharged when SHDN /UVLO falls below its threshold,
during an overtemperature event or during an INTV CC
undervoltage event. During start-up with SHDN /UVLO,
charging of the soft-start capacitor is enabled after the
first PWM high period.
Power MOSFET Selection
For applications operating at high input or output voltages,
the power NMOS FET switch is typically chosen for drain
voltage V DS rating and low gate charge Q G . Consideration
of switch on-resistance, R DS(ON) , is usually secondary be-
cause switching losses dominate power loss. The INTV CC
regulator on the LT3755 has a fixed current limit to protect
the IC from excessive power dissipation at high V IN , so the
FET should be chosen so that the product of Q G at 7V and
switching frequency does not exceed the INTV CC current
limit. For driving LEDs be careful to choose a switch with
a V DS rating that exceeds the threshold set by the FB pin
in case of an open-load fault. Several MOSFET vendors
are listed in Table 3. The MOSFETs used in the application
circuits in this data sheet have been found to work well
with the LT3755. Consult factory applications for other
recommended MOSFETs.
Table 3. MOSFET Manufacturers
VENDOR WEB
Vishay Siliconix www.vishay.com
Fairchild www.fairchildsemi.com
International Rectifier www.irf.com
37551fd
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相关代理商/技术参数 |
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| LT3755IMSE-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:40VIN, 75VOUT LED Controller |
| LT3755IMSE-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:40VIN, 75VOUT LED Controller |
| LT3755IUD#PBF | 功能描述:IC LED DRVR HP CONST CURR 16-QFN 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 |
| LT3755IUD#PBF | 制造商:Linear Technology 功能描述:LED DRIVER PWM 1MHZ QFN-16 制造商:Linear Technology 功能描述:LED DRIVER, PWM, 1MHZ, QFN-16 |
| LT3755IUD#TRPBF | 功能描述:IC LED DRVR HP CONST CURR 16-QFN 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 |
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