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參數(shù)資料
| 型號(hào)： | LM2791 |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | LED驅(qū)動(dòng)器 |
| 英文描述： | Current Regulated Switched Capacitor LED Driver with Analog Brightness Control |
| 中文描述： | 電流調(diào)節(jié)開(kāi)關(guān)電容LED與模擬亮度控制驅(qū)動(dòng)器 |
| 文件頁(yè)數(shù)： | 8/11頁(yè) |
| 文件大?。?/td> | 226K |
| 代理商： | LM2791 |
Circuit Description
The LM2791 provides two matched current sources for driv-
ing high forward voltage drop LEDs from Li-Ion battery
sources. The device has on-chip current regulators which
are composed of current mirrors with a 25 to 1 ratio. The
mirrors control the LED current without using current limiting
resistors in the LED current path. The device can drive up to
a total of 36mA through the LEDs.
The LED brightness can be controlled by both analog and or
digital methods. The digital technique uses a PWM (Pulse
Width Modulation) signal applied to the shutdown input. The
analog technique applies an analog voltage to the brightness
(BRGT) pin (see Application Information sections). For low-
est cost, the LM2791 can be used for constant brightness by
grounding BRGT and enabling the shutdown pin.
Application Information
SOFT START
LM2791 includes a soft start function to reduce the inrush
currents and high peak current during power up of the de-
vice. Soft start is implemented internally by ramping the
bandgap more slowly than the applied voltage. This is done
by holding the bandgap in shutdown for a short time. During
soft start, the switch resistances limit the inrush current used
to charge the flying and hold capacitors.
SHUTDOWN MODE
A shutdown pin (SD or /SD) is available to disable the
LM2791 and reduce the quiescent current to 1μA maximum.
The LM2791 is available with both senses of shutdown
polarity.
During normal operation mode of the ’-L’ options, an active
high logic signal to the SD pin or tying the SD pin to V
, will
enable the device. Pulling SD low or connectingSD to
ground will disable the device.
During normal operation mode of the ’-H’ options, an active
low logic signal to the SD pin or tying the SD pin to GND, will
enable the device. Pulling SD high or connecting SD to V
IN
will disable the device.
CAPACITOR SELECTION
Low equivalent series resistance (ESR) capacitors such as
X5R or X7R are recommended to be used for C
, C1, C2,
and C
for best performance. Ceramic capacitors with
less than or equal to 0.3 ohms ESR value are recommended
for this application.
Table 1
below lists suggested capacitor
suppliers for the typical application circuit.
TABLE 1. Low ESR Capacitor Manufactures
Manufacturer
TDK
Contact
(847) 803
6100
(800) 831
9172
(800) 348
2496
website
www.component.tdk.com
MuRata
www.murata.com
Taiyo Yuden
www.t-yuden.com
SCHOTTKY DIODE SELECTION
A schottky diode (D1) must be used between V
and P
for proper operation. During start-up, the low voltage drop
across this diode is used to charge C
and start the
oscillator. It is necessary to protect the device from
20018304
FIGURE 1.
L
www.national.com
8
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM2791LD-L | Current Regulated Switched Capacitor LED Driver with Analog Brightness Control |
| LM2791LDX-H | Current Regulated Switched Capacitor LED Driver with Analog Brightness Control |
| LM2791LDX-L | Current Regulated Switched Capacitor LED Driver with Analog Brightness Control |
| LM2792LD-H | Current Regulated Switched Capacitor LED Driver with Analog Brightness Control |
| LM2792 | Current Regulated Switched Capacitor LED Driver with Analog Brightness Control |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2791B WAF | 制造商:Texas Instruments 功能描述: |
| LM2791LD-H | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Current Regulated Switched Capacitor LED Driver with Analog Brightness Control |
| LM2791LD-H/NOPB | 功能描述:IC LED DRIVR WHITE BCKLGT 10-LLP RoHS:是 類別:集成電路 (IC) >> PMIC - LED 驅(qū)動(dòng)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(dòng)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(yè)面:1371 (CN2011-ZH PDF) 其它名稱:BD1603NUV-E2CT |
| LM2791LD-L | 功能描述:LED照明驅(qū)動(dòng)器 RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
| LM2791LD-L/NOPB | 功能描述:LED照明驅(qū)動(dòng)器 RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
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