參數(shù)資料
型號(hào)： LT3486
廠商： Linear Technology Corporation
英文描述： Dual 1.3A White LED Step-Up Converters with Wide Dimming
中文描述： 雙1.3a標(biāo)準(zhǔn)白光LED升壓轉(zhuǎn)換器具有較寬的亮度調(diào)節(jié)，
文件頁(yè)數(shù)： 9/20頁(yè)
文件大?。?/td> 839K
代理商： LT3486
LT3486
9
3486f
output open circuit are shown in the Typical Performance
Characteristics graphs.
Figure 3a shows the transient response of switcher 1 with
the LEDs disconnected from the output. When the LED1
string is disconnected from the output, the voltage at
the feedback pin (FB1) drops to 0V. As a result, the error
amplifier charges up the V
C
node to the clamp voltage
level of 1.5V (typ). The converter starts switching at peak
current limit and ramps up the output voltage. When the
output voltage reaches the OVP clamp voltage level of
36V (typ), the LT3486 shuts off the converter by pulling
the V
C
node to ground. The converter then regulates the
output voltage at 36V (typ) by switching at a very low
frequency.
In the event one of the converters has an output open-
circuit, its output voltage will be clamped at 36V (typ).
However, the other converter will continue functioning
properly. The photo in Figure 3b shows circuit operation
with converter 1 output open-circuit and converter 2 driving
eight LEDs at 25mA. Converter 1 starts switching at a very
low frequency, reducing its input current.
Soft-Start
The LT3486 has a separate internal soft-start circuitry for
each converter. Soft-start helps to limit the inrush current
during start-up. Soft-start is achieved by clamping the
output of the error amplifier during the soft-start period.
This limits the peak inductor current and ramps up the
output voltage in a controlled manner.
The converter enters into soft-start mode whenever the
respective CTRL pin is pulled from low to high. Figure 4
shows the start-up waveforms with converter 2 driving
eight LEDs at 25mA. The filtered input current, as shown
in Figure 4, is well controlled. The soft-start circuit is more
effective when driving a smaller number of LEDs.
Undervoltage Lockout
The LT3486 has an undervoltage lockout circuit which
shuts down both the converters when the input voltage
drops below 2.1V (typ). This prevents the converter to
operate in an erratic mode when powered from low supply
voltages.
Overtemperature Protection
The maximum allowable junction temperature for LT3486 is
125°C. In normal operation, the IC’s junction temperature
should be kept below 125°C at an ambient temperature of
85°C or less. If the junction temperature exceeds 150°C, the
internal thermal shutdown circuitry kicks in and turns-off
both the converters. The converters will remain off until
the die temperature falls below 150°C.
OPERATIOU
V
20V/DIV
V
C1
2V/DIV
I
L1
1A/DIV
100
μ
s/DIV
LED1 DISCONNECTED
AT THIS INSTANT
3486 F03a
V
= 3.6V
CIRCUIT OF
FRONT PAGE
APPLICATION
V
1V/DIV
AC COUPLED
I
L1
1A/DIV
I
L2
500mA/DIV
2ms/DIV
3486 F03b
V
IN
= 3.6V
CIRCUIT OF FRONT PAGE APPLICATION
LED1 DISCONNECTED
Figure 3b. Switching Waveforms with Output 1 Open Circuit
V
10V/DIV
V
200mV/DIV
I
IN
200mA/DIV
CTRL2
5V/DIV
0.5ms/DIV
3486 F04
V
IN
= 3.6V
8 LEDs, 25mA
CIRCUIT OF FRONT PAGE APPLICATION
Figure 3a. Transient Response of Switcher 1 with LED1
Disconnected from the Output
Figure 4. Start-Up Waveforms
相關(guān)PDF資料
PDF描述
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LT3486_08 制造商:LINER 制造商全稱(chēng):Linear Technology 功能描述:Dual 1.3A White LED Step-Up Converters with Wide Dimming
LT3486EDHC 制造商:LINER 制造商全稱(chēng):Linear Technology 功能描述:Dual 1.3A White LED Step-Up Converters with Wide Dimming
LT3486EDHC#PBF 功能描述:IC LED DRIVR WHITE BCKLGT 16-DFN RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - LED 驅(qū)動(dòng)器 系列:- 標(biāo)準(zhǔn)包裝:6,000 系列:- 恒定電流:- 恒定電壓:- 拓?fù)?開(kāi)路漏極，PWM 輸出數(shù):4 內(nèi)部驅(qū)動(dòng)器:是 類(lèi)型 - 主要:LED 閃爍器 類(lèi)型 - 次要:- 頻率:400kHz 電源電壓:2.3 V ~ 5.5 V 輸出電壓:- 安裝類(lèi)型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤(pán) 供應(yīng)商設(shè)備封裝:8-HVSON 包裝:帶卷 (TR) 工作溫度:-40°C ~ 85°C 其它名稱(chēng):935286881118PCA9553TK/02-TPCA9553TK/02-T-ND
LT3486EDHC#TRPBF 功能描述:IC LED DRIVR WHITE BCKLGT 16-DFN RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - LED 驅(qū)動(dòng)器 系列:- 標(biāo)準(zhǔn)包裝:6,000 系列:- 恒定電流:- 恒定電壓:- 拓?fù)?開(kāi)路漏極，PWM 輸出數(shù):4 內(nèi)部驅(qū)動(dòng)器:是 類(lèi)型 - 主要:LED 閃爍器 類(lèi)型 - 次要:- 頻率:400kHz 電源電壓:2.3 V ~ 5.5 V 輸出電壓:- 安裝類(lèi)型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤(pán) 供應(yīng)商設(shè)備封裝:8-HVSON 包裝:帶卷 (TR) 工作溫度:-40°C ~ 85°C 其它名稱(chēng):935286881118PCA9553TK/02-TPCA9553TK/02-T-ND
LT3486EFE 制造商:Linear Technology 功能描述:LED DRVR 16Segment 3.3V/5V/9V/12V/15V/18V 16-Pin TSSOP EP
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