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參數(shù)資料
| 型號： | LM2707MFX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 顯示驅(qū)動器 |
| 英文描述： | Inductive-Boost Series LED Driver with Programmable Oscillator Frequency |
| 中文描述： | LED DISPLAY DRIVER, PDSO8 |
| 封裝： | SOT-23, 8 PIN |
| 文件頁數(shù)： | 15/19頁 |
| 文件大?。?/td> | 1039K |
| 代理商： | LM2707MFX |
Application Information
(Continued)
Table 1. Time-Averaged LED Current vs. PWM Frequency and Duty Cycle
PWM Frequency
200 Hz
1 kHz
10 kHz
20 kHz
40 kHz
50 kHz
V
IN
= 3.6V, 4 LEDs, R
FB
= 34
, I
LED
= 14.9mA when V(EN) is HIGH.
D = 10%
2.3
3.7
2.6
1.0
OFF
OFF
D = 20%
3.8
6.0
5.9
4.7
1.8
OFF
D = 30%
5.3
7.4
9.1
8.6
5.1
5.7
D = 50%
8.2
10.0
13.4
13.6
12.0
10.3
D = 90%
13.9
14.4
14.8
14.8
14.8
14.8
A benefit of PWM brightness adjustment is the characteristic
that LEDs are driven with the same current level (max cur-
rent) at all brightness levels. Other methods that adjust
brightness by changing the DC forward current of the LEDs
may see a slight change in color at different brightness
levels.
With the addition of an external resistor, an analog voltage
can be used to adjust LED brightness, as shown in
Figure
10
. When the analog voltage is above the feedback voltage,
0.515V (typ.), the analog voltage source adds current to
feedback node. In order to keep the feedback voltage regu-
lated, the LM2707 responds by reducing the current through
the LEDs. Conversely, LED current increases when the ana-
log voltage is below the feedback voltage.
A 4-level digital brightness adjustment, shown in
Figure 11
,
can be implemented with a pair of external resistors and two
digital logic signals. The workings of the circuit are similar to
the analog voltage control: LED currents are set based on
the current that is added to or removed from the FB node
from the digital voltage supplies.
20099235
FIGURE 10. LM2707 LED-Drive Circuit with Analog Voltage Brightness Control
L
www.national.com
15
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| LM2707MFX/NOPB | 功能描述:IC LED DRVR WHITE BCKLGT SOT23-8 RoHS:是 類別:集成電路 (IC) >> PMIC - LED 驅(qū)動器 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 恒定電流:- 恒定電壓:- 拓?fù)?PWM，切換式電容器（充電泵） 輸出數(shù):1 內(nèi)部驅(qū)動器:是 類型 - 主要:背光 類型 - 次要:白色 LED 頻率:642kHz 電源電壓:2.7 V ~ 5.5 V 輸出電壓:5V 安裝類型:表面貼裝 封裝/外殼:10-VFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:10-VSON 包裝:剪切帶 (CT) 工作溫度:-30°C ~ 85°C 產(chǎn)品目錄頁面:1371 (CN2011-ZH PDF) 其它名稱:BD1603NUV-E2CT |
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