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參數(shù)資料
| 型號： | LM27961 |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | LED驅(qū)動器 |
| 英文描述： | Dual-Display White LED Driver with 3/2x Switched Capacitor Boost |
| 中文描述： | 雙顯示器白光LED驅(qū)動3/2x開關(guān)電容升壓 |
| 文件頁數(shù)： | 9/13頁 |
| 文件大?。?/td> | 711K |
| 代理商： | LM27961 |
Block Diagram
20127903
Circuit Description
OVERVIEW
The LM27961 is primarily intended for Lithium-Ion battery
driven white-LED drive applications, and is well suited to
drive white LEDs that are used for backlighting small-format
displays. The part has seven matched constant-current out-
puts, each capable of driving up to 20mA (or more) through
white LEDs. The well-matched current sources ensure the
current through all the LEDs is virtually identical. This keeps
brightness of all LEDs matched to near perfection so that
they can provide a consistent backlight over the entire dis-
play.
CHARGE PUMP
The core of the LM27961 is a 1.5x/1x dual-mode charge
pump. The input of the charge pump is connected to the V
IN
pin. The recommended input voltage range of the LM27961
is 2.7V to 5.5V. The output of the charge pump is the P
pin (“Pump OUTput”). The output voltage of the charge
pump is unregulated and varies with input voltage and load
current.
The charge pump operates in the 1.5x mode when the input
voltage is below 4.75V (typ.). In this mode, the input-to-
output voltage gain of the charge pump is 1.5, and the
voltage at the output of the charge pump will be approxi-
mately 1.5x the input voltage (V(P
)
≈
1.5 * V
). When in
the 1.5x mode, the charge pump provides the voltage boost
that is required to drive white LEDs from a Li-Ion battery.
(White LEDs typically have a forward voltage in the range of
3.3V to 4.0V. A Li-Ion battery typically is not considered to be
fully discharged until the battery voltage falls to 3.0V (ap-
prox.) )
The charge pump operates in the 1x mode when the input
voltage is above 4.75V (typ.). In these conditions, voltage
boost is not required to drive the LEDs, so the charge pump
merely passes the input voltage to P
OUT
(V(P
OUT
)
≈
V
IN
).
This reduces the input current and the power dissipation of
the LM27961 when the input voltage is high.
REGULATED CURRENT OUTPUTS
The matched current outputs are generated with a precision
current mirror that is biased off the charge pump output.
Matched currents are ensured with the use of tightly
matched internal devices and internal mismatch cancellation
circuitry.
There are seven regulated current outputs. These seven
outputs are split into two groups, a group of 4 common
L
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相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM27961TL | Dual-Display White LED Driver with 3/2x Switched Capacitor Boost |
| LM27961TLX | Dual-Display White LED Driver with 3/2x Switched Capacitor Boost |
| LM2798 | WIRE |
| LM2798MM-1.5 | 120mA High Efficiency Step-Down Switched Capacitor Voltage Converter with Voltage Monitoring |
| LM2798MMX-1.8 | 120mA High Efficiency Step-Down Switched Capacitor Voltage Converter with Voltage Monitoring |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM27961AW WAF | 制造商:Texas Instruments 功能描述: |
| LM27961TL | 制造商:Texas Instruments 功能描述:IC WLED DRIVER POWERWISE |
| LM27961TL/NOPB | 功能描述:IC LED DRVR WHT BCKLT 18USMD 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 |
| LM27961TLEV | 功能描述:LED 照明開發(fā)工具 LM27961 EVAL BOARD RoHS:否 制造商:Fairchild Semiconductor 產(chǎn)品:Evaluation Kits 用于:FL7732 核心: 電源電壓:120V 系列: 封裝: |
| LM27961TLX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual-Display White LED Driver with 3/2x Switched Capacitor Boost |
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