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参数资料
| 型号： | LM2795TLX/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 13/23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
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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| 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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