- 您现在的位置：买卖IC网 > Sheet目录337 > LT3492IFE#TRPBF (Linear Technology)IC LED DVR HP CONST CURR 28TSSOP
LT3492
APPLICATIONS INFORMATION
is similar to your application and tune the compensation
network to optimize the performance. The stability, PWM
dimming waveforms and the start-up time should be
checked across all operating conditions.
Open-LED Protection
The LT3492 has open-LED protection for all the three
converters. As shown in Figure 1, the OVP1 pin receives
the output voltage (the voltage across the output capacitor)
feedback signal from an external resistor divider. OVP1
voltage is compared with a 1V internal voltage reference by
comparator A6. In the event the LED string is disconnected
Input Capacitor Selection
For proper operation, it is necessary to place a bypass
capacitor to GND close to the V IN pin of the LT3492. A
1μF or greater capacitor with low ESR should be used. A
ceramic capacitor is usually the best choice.
In the buck mode con?guration, the capacitor at PV IN has
large pulsed currents due to the current returned though
the Schottky diode when the switch is off. For the best
reliability, this capacitor should have low ESR and ESL
and have an adequate ripple current rating. The RMS
input current is:
or fails open, converter 1 output voltage will increase, caus-
ing OVP1 voltage to increase. When OVP1 voltage exceeds
I IN(RMS) = I LED ?
( 1 – D ) ? D
1V, the power switch Q1 will turn off, and cause the output
voltage to decrease. Eventually, OVP1 will be regulated to
1V and the output voltage will be limited. In the event one
of the converters has an open-LED protection, the other
converters will continue functioning properly.
Switching Frequency and Soft-Start
The LT3492 switching frequency is controlled by FADJ
pin voltage. Setting FADJ voltage to be less than 1V will
reduce switching frequency.
If FADJ voltage is higher than 1V, the default switch-
ing frequency is 2.1MHz. In general, a lower switching
frequency should be used where either very high or very
low switch duty cycle is required or higher ef?ciency is
desired. Selection of a higher switching frequency will
allow use of low value external components and yield a
smaller solution size and pro?le.
As a cautionary note, operation of the LT3492 at a com-
bination of high switching frequency with high output
voltage and high switch current may cause excessive
internal power dissipation. Consideration should be given
to selecting a switching frequency less than 1MHz if these
conditions exist.
Connecting FADJ pin to a lowpass ?lter (R5 and C4 in
Figure 1) from the REF pin provides a soft-start function.
During start-up, FADJ voltage increases slowly from 0V
to the setting voltage. As a result, the switching frequency
increases slowly to the setting frequency. This function
limits the inrush current during start-up.
where D is the switch duty cycle. A 1μF ceramic type ca-
pacitor placed close to the Schottky diode and the ground
plane is usually suf?cient for each channel.
Output Capacitor Selection
The selection of output ?lter capacitor depends on the load
and converter con?guration, i.e., step-up or step-down.
For LED applications, the equivalent resistance of the LED
is typically low, and the output ?lter capacitor should be
large enough to attenuate the current ripple.
To achieve the same LED ripple current, the required ?lter
capacitor value is larger in the boost and buck-boost mode
applications than that in the buck mode applications. For
the LED buck mode applications at 1.3MHz, a 0.22μF ce-
ramic capacitor is usually suf?cient for each channel. For
the LED boost and buck-boost applications at 1.3MHz, a
1μF ceramic capacitor is usually suf?cient for each chan-
nel. Lower switching frequency requires proportionately
higher capacitor values. If higher LED current ripple can
be tolerated, a lower output capacitance can be selected
to reduce the capacitor’s cost and size.
Use only ceramic capacitors with X7R or X5R dielectric,
as they are good for temperature and DC bias stability of
the capacitor value. All ceramic capacitors exhibit loss of
capacitance value with increasing DC voltage bias, so it
may be necessary to choose a higher value capacitor to get
the required capacitance at the operation voltage. Always
check that the voltage rating of the capacitor is suf?cient.
Table 1 shows some recommended capacitor vendors.
3492fa
10
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
LT3496IUFD#PBF
IC LED DRVR WHT/RGB BCKLT 28-QFN
LT3497EDDB#TRMPBF
IC LED DRIVR WHITE BCKLGT 10-DFN
LT3498EDDB#TRPBF
IC LED DRVR WT/OLED BCKLGT 12DFN
LT3517HUF#PBF
IC LED DRIVER AUTOMOTIVE 16-QFN
LT3519EMS-2#PBF
IC LED DRVR HP CONST CURR 16MSOP
LT3590ESC8#TRMPBF
IC LED DRVR WHITE BCKLGT SC-70-8
LT3591EDDB#TRMPBF
IC LED DRIVER WHITE BCKLGT 8-DFN
LT3593ES6#TRMPBF
IC LED DRIVR WHITE BCKLGT TSOT-6
相关代理商/技术参数
LT3492IFEPBF
制造商:LINER 制造商全称:Linear Technology 功能描述:Triple Output LED Driver with 3000:1 PWM Dimming
LT3492IFETRPBF
制造商:LINER 制造商全称:Linear Technology 功能描述:Triple Output LED Driver with 3000:1 PWM Dimming
LT3492IUFD
制造商:LINER 制造商全称:Linear Technology 功能描述:Triple Output LED Driver with 3000:1 PWM Dimming
LT3492IUFD#PBF
功能描述:IC LED DRIVER TRIPLE 28QFN 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
LT3492IUFD#TRPBF
功能描述:IC LED DVR TRPL PWM DIM 28TSSOP 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
LT3492IUFDPBF
制造商:LINER 制造商全称:Linear Technology 功能描述:Triple Output LED Driver with 3000:1 PWM Dimming
LT3492IUFDTRPBF
制造商:LINER 制造商全称:Linear Technology 功能描述:Triple Output LED Driver with 3000:1 PWM Dimming
LT3493
制造商:LINER 制造商全称:Linear Technology 功能描述:1.2A, 750kHz Step-Down Switching Regulator in 2mm × 3mm DFN