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| 型号： | LM2795EVAL |
| 厂商： | National Semiconductor |
| 文件页数： | 13/23页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION LM2795 |
| 标准包装： | 1 |
| 电流 - 输出 / 通道： | 80mA |
| 输出及类型： | 4，非隔离 |
| 输出电压： | 4V |
| 特点： | 充电泵 |
| 输入电压： | 2.7 ~ 5.5 V |
| 已供物品： | 板 |
| 已用 IC / 零件： | LM2795 |
| 相关产品： | LM2795TLX-ND - IC LED DRVR WHT BCKLT 14USMD LM27953TLX-ND - IC LED DRVR WHT BCKLT 18USMD LM27952SDX-ND - IC LED DRIVR WHITE BCKLGT 14-LLP LM27951SDX-ND - IC LED DRIVR WHITE BCKLGT 14-LLP LM2795BLDKR-ND - IC LED DRVR WHT BCKLT 14USMD LM27953TLDKR-ND - IC LED DRVR WHT BCKLT 18USMD LM27952SDDKR-ND - IC LED DRIVR WHITE BCKLGT 14-LLP LM27951SDDKR-ND - IC LED DRIVR WHITE BCKLGT 14-LLP LM27952SDCT-ND - IC LED DRIVR WHITE BCKLGT 14-LLP LM27951SDCT-ND - IC LED DRIVR WHITE BCKLGT 14-LLP 更多... |
SNVS168L – JANUARY 2002 – REVISED MAY 2013
The voltage at P OUT is dependent on the input voltage supplied to the LM2794/5, the total LM2794/5 output
current, and the output resistance (R OUT ) of the LM2794/5 charge pump. Output resistance is a model of the
switching losses of the charge pump. Resistances of the internal charge pump switches (MOS transistors) are a
primary component of the LM2794/5 output resistance. Typical LM2794/5 output resistance is 3.0 ? . For worst-
case design calculations, using an output resistance of 3.5 ? is recommended. (Worst-case recommendation
accounts for parameter shifts from part-to-part variation and applies over the full operating temperature range).
C 1
1 … F
C 2
1 … F
3.0V
V IN
C 1 -
C 1 + C 2 -
C 2 +
P OUT
(3/2) V IN = approx. 4.5V
Keypad LEDs
C IN
1 … F
C POUT
1 … F
D K1
D K2
D KX
BRGT
LM2794/95
GND
5mA
R SET
D 1
D 2
D 3
D 4
*Optional
124 :
15mA each
= 60 mA
Independent
Shutdown
Total
Figure 23. Keypad LEDs Connected to P OUT
Output resistance results in droop in the P OUT voltage proportional to the amount of current delivered by the
pump. The P OUT voltage is an important factor in determining the total output current capability of an application.
Taking total output current to be the sum of all D X output currents plus the current delivered through the P OUT pin,
the voltage at P OUT can be predicted with the following equations:
I TOTAL = I D1 + I D2 + I D3 + I D4 + I POUT
V POUT = 1.5 × V IN ? I TOTAL × R OUT
(1)
(2)
LED HEADROOM VOLTAGE (V HR )
Four current sources are connected internally between P OUT and D 1 -D 4 . The voltage across each current source,
(V POUT ? V DX ), is referred to as headroom voltage (V HR ). The current sources require a sufficient amount of
headroom voltage to be present across them in order to regulate properly. Minimum required headroom voltage
is proportional to the current flowing through the current source, as dictated by the equation:
V HR-MIN = k HR × I DX
(3)
The parameter k HR , typically 20mV/mA in the LM2794/5, is a proportionality constant that represents the ON-
resistance of the internal current mirror transistors. For worst-case design calculations, using a k HR of 25mV/mA
is recommended. (Worst-case recommendation accounts for parameter shifts from part-to-part variation and
applies over the full operating temperature range). Figure 24 shows how output current of the LM2794/5 varies
with respect to headroom voltage.
Copyright ? 2002–2013, Texas Instruments Incorporated
Product Folder Links: LM2794 LM2795
13
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| LM2795TL | 功能描述:IC LED DRVR WHT BCKLT 14MICROSMD RoHS:否 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 |
| LM2795TLX | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Current Regulated Switched Capacitor LED Supply with Analog and PWM Brightness Control |
| LM2795TLX/NOPB | 功能描述:LED照明驱动器 RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| LM2796 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Dual-Display White LED Driver with 3/2x Switched Capacitor Boost |
| LM27961 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Dual-Display White LED Driver with 3/2x Switched Capacitor Boost |
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