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| 型号： | LM2795TLX/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 10/23页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR WHT BCKLT 14USMD |
| 标准包装： | 3,000 |
| 恒定电流： | 是 |
| 拓扑： | PWM，切换式电容器（充电泵） |
| 输出数： | 4 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 325kHz ~ 515kHz |
| 电源电压： | 2.7 V ~ 5.5 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 14-WFBGA |
| 供应商设备封装： | 14-TuSMD |
| 包装： | 带卷 (TR) |
| 工作温度： | -30°C ~ 85°C |
| 配用： | LM2795EVAL-ND - BOARD EVALUATION LM2795 |
| 其它名称： | LM2795TLX |
SNVS168L – JANUARY 2002 – REVISED MAY 2013
APPLICATION INFORMATION
CIRCUIT DESCRIPTION
The LM2794/5 is a 1.5x/1x CMOS charge pump with four matched constant current outputs, each capable of
driving up to 20mA through White LEDs. This device operates over the extended Li-Ion battery range from 2.7V
to 5.5V. The LM2794/5 has four regulated current sources connected to the device's 1.5x charge pump output
(P OUT ). At input voltages below 4.7V (typ.), the charge-pump provides the needed voltage to drive high forward
voltage drop White LEDs. It does this by stepping up the P OUT voltage 1.5 times the input voltage. The charge
pump operates in Pass Mode, providing a voltage on P OUT equal to the input voltage, when the input voltage is at
or above 4.7V (typ.). The device can drive up to 80mA through any combination of LEDs connected to the
constant current outputs D 1 -D 4 .
To set the LED drive current, the device uses a resistor connected to the I SET pin to set a reference current. This
reference current is then multiplied and mirrored to each constant current output. The LED brightness can then
be controlled by analog and/or digital methods. Applying an analog voltage in the range of 0V to 3.0V to the
Brightness pin (BRGT) adjusts the dimming profile of the LEDs. The digital technique uses a PWM (Pulse Width
Modulation) signal applied to the Shutdown pin (SD). (see I SET AND BRGT PINS ).
SOFT START
Soft start is implemented internally by ramping the reference voltage more slowly than the applied voltage.
During soft start, the current through the LED outputs will ramp up in proportion to the rate that the reference
voltage is being ramped up.
SHUTDOWN MODE
The shutdown pin (SD) disables the part and reduces the quiescent current to 2.3μA (typ.).
The LM2795 has an active-high shutdown pin (HIGH = shutdown, LOW = operating). An internal pull-up is
connected between SD and V IN of the LM2795. This allows the use of open-drain logic control of the LM2795
shutdown, as shown in Figure 22 . The LM2795 SD pin can also be driven with a rail-to-rail CMOS logic signal.
LM2795
V IN
*Only on
*
LM2795
Shutdown
Control
SD
10 P A
Figure 22. Open-Drain Logic Shutdown Control
The LM2794 has an active-low shutdown pin (LOW = shutdown, HIGH = operating). The LM2794 SD pin can be
driven with a low-voltage CMOS logic signal (1.5V logic, 1.8V logic, etc). There is no internal pull-up or pull-down
on the SD pin of the LM2794.
CAPACITOR SELECTION
The LM2794/5 requires 4 external capacitors for proper operation. Surface-mount multi-layer ceramic capacitors
are recommended. These capacitors are small, inexpensive and have very low equivalent series resistance
(ESR, ≤ 15m ? typ.). Tantalum capacitors, OS-CON capacitors, and aluminum electrolytic capacitors are generally
not recommended for use with the LM2794/5 due to their high ESR, as compared to ceramic capacitors.
10
Product Folder Links: LM2794 LM2795
Copyright ? 2002–2013, Texas Instruments Incorporated
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| LM27961TL/NOPB | 功能描述:IC LED DRVR WHT BCKLT 18USMD RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:1 系列:- 恒定电流:- 恒定电压:- 拓扑:PWM，切换式电容器（充电泵） 输出数:1 内部驱动器:是 类型 - 主要:背光 类型 - 次要:白色 LED 频率:642kHz 电源电压:2.7 V ~ 5.5 V 输出电压:5V 安装类型:表面贴装 封装/外壳:10-VFDFN 裸露焊盘 供应商设备封装:10-VSON 包装:剪切带 (CT) 工作温度:-30°C ~ 85°C 产品目录页面:1371 (CN2011-ZH PDF) 其它名称:BD1603NUV-E2CT |
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