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參數資料
| 型號： | 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標準白光LED升壓轉換器具有較寬的亮度調節(jié)， |
| 文件頁數： | 14/20頁 |
| 文件大小： | 839K |
| 代理商： | LT3486 |
LT3486
14
3486f
S U
APPLICATIO
the figure. A PWM logic input is applied to the gate of the
NMOS and the PWM pin of the LT3486. When the PWM
input is taken high, the LEDs are connected to the R
FB
resistor and a current I
LED
= 200mV/R
FB
flows through
the LEDs. When the PWM input is taken low, the LEDs are
disconnected and turn off. The low PWM input applied to
the LT3486 ensures that the respective converter turns
off and its V
C
pin goes high impedance. This ensures that
the capacitor connected to the V
C
pin retains its voltage
which in turn allows the LEDs to turn on faster, as shown
in Figure 8(b). The CTRL pin is not used to modulate the
LED current in the scheme. It can be connected to a supply
voltage greater than 1.8V.
The dimming control pins (PWM1, PWM2) can be used
to extend the dimming range for the individual switching
converters. The LED current can be controlled down to
μA levels by feeding a PWM signal with frequencies in the
range of 80Hz to 50kHz. The LED current can be controlled
by PWM frequencies above 50kHz but the controllable
current decreases with increasing frequency. Pulling the
PWM pins below 0.4V disables the respective switcher.
Taking it higher than 0.9V resumes normal operation.
Connect these pins to 0.9V or higher if not in use.
W
U
U
Figure 10. Recommended Layout for LT3486
Figure 9 shows the LED current variation vs PWM duty
cycle. The LED current is controlled by applying a PWM
of frequency 100Hz, 1kHz and 25kHz to the circuit of
Figure 8a. As seen in the curves, the LED string is able to
get a wide (1000:1) dimming range with PWM frequency of
100Hz. The dimming range decreases as PWM frequency
goes up.
Board Layout Consideration
As with all switching regulators, careful attention must be
paid to the PCB board layout and component placement.
To prevent electromagnetic interference (EMI) problems,
proper layout of high frequency switching paths is essential.
Minimize the length and area of all traces connected to the
switching node pins (SW1 and SW2). Keep the feedback
pins (FB1 and FB2) away from the switching nodes.
The DFN and FE packages both have an exposed paddle
that must be connected to the system ground. The ground
connection for the feedback resistors should be tied directly
to the ground plane and not shared with any other compo-
nent, except the R
T
resistor, ensuring a clean, noise-free
connection. Recommended component placement for the
DFN package is shown in the Figure 10.
Figure 9. LED Current Variation vs PWM Duty Cycle
PWM DUTY CYCLE (%)
0.1
L
1
10
100
0.01
1
10
100
3486 F09
0.01
0.1
PWM FREQ = 100Hz
PWM FREQ = 1kHz
PWM FREQ = 25kHz
16
15
14
13
12
11
10
9
17
1
2
3
4
5
6
7
8
3486 F10
OVP1
V
OUT1
V
OUT2
FB1
FB2
LED1
LED2
CTRL1
CTRL2
V
IN
SW1
SW2
V
IN
V
IN
R
T
V
C1
PWM1
REF
OVP2
SHDN
V
C2
PWM2
VIAs TO V
IN
PLANE
VIAs TO GROUND PLANE
VIAs TO V
IN
PLANE
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| LT3486EDHC | Dual 1.3A White LED Step-Up Converters with Wide Dimming |
| LT3486EFE | Dual 1.3A White LED Step-Up Converters with Wide Dimming |
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LT3486_08 | 制造商:LINER 制造商全稱: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: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 類別:集成電路 (IC) >> PMIC - LED 驅動器 系列:- 標準包裝:6,000 系列:- 恒定電流:- 恒定電壓:- 拓撲:開路漏極，PWM 輸出數:4 內部驅動器:是 類型 - 主要:LED 閃爍器 類型 - 次要:- 頻率:400kHz 電源電壓:2.3 V ~ 5.5 V 輸出電壓:- 安裝類型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤 供應商設備封裝:8-HVSON 包裝:帶卷 (TR) 工作溫度:-40°C ~ 85°C 其它名稱:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
| LT3486EDHC#TRPBF | 功能描述:IC LED DRIVR WHITE BCKLGT 16-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - LED 驅動器 系列:- 標準包裝:6,000 系列:- 恒定電流:- 恒定電壓:- 拓撲:開路漏極，PWM 輸出數:4 內部驅動器:是 類型 - 主要:LED 閃爍器 類型 - 次要:- 頻率:400kHz 電源電壓:2.3 V ~ 5.5 V 輸出電壓:- 安裝類型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤 供應商設備封裝:8-HVSON 包裝:帶卷 (TR) 工作溫度:-40°C ~ 85°C 其它名稱: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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