参数资料
型号: LM2794BL
厂商: National Semiconductor
文件页数: 16/23页
文件大小: 0K
描述: IC LED DRVR WHT BCKLT 14USMD
标准包装: 1
恒定电流:
拓扑: PWM,切换式电容器(充电泵)
输出数: 4
内部驱动器:
类型 - 主要: 背光
类型 - 次要: 白色 LED
频率: 325kHz ~ 675kHz
电源电压: 2.7 V ~ 5.5 V
输出电压: 3.8V
安装类型: 表面贴装
封装/外壳: 14-VFBGA
供应商设备封装: 14-uSMD
包装: 标准包装
工作温度: -30°C ~ 85°C
配用: LM2794EVAL-ND - BOARD EVALUATION LM2794
其它名称: LM2794BLDKR
SNVS168L – JANUARY 2002 – REVISED MAY 2013
POWER EFFICIENCY
Figure 27 shows the efficiency of the LM2794/5. The change in efficiency shown by the graph comes from the
transition from Pass Mode to a gain of 1.5.
Efficiency (E) of the LM2794/5 is defined here as the ratio of the power consumed by LEDs (P LED ) to the power
drawn from the input source (P IN ). In the equations below, I Q is the quiescent current of the LM2794/5, I LED is the
current flowing through one LED, V LED is the forward voltage at that LED current, and N is the number of LEDs
connected to the regulated current outputs. In the input power calculation, the 1.5 represents the switched
capacitor gain configuration of the LM2794/5.
P LED = N × V LED × I LED
P IN = V IN × I IN
P IN = V IN × (1.5 × N × I LED + I Q )
E = (P LED ÷ P IN )
(9)
(10)
(11)
(12)
Efficiency, as defined here, is in part dependent on LED voltage. Variation in LED voltage does not affect power
consumed by the circuit and typically does not relate to the brightness of the LED. For an advanced analysis, it is
recommended that power consumed by the circuit (V IN x I IN ) be evaluated rather than power efficiency. Figure 28
shows the power consumption of the LM2794/5 Typical Application Circuit.
Figure 27. Efficiency vs V IN
4 LEDs, V LED = 3.6V, I LED = 15mA
450
430
410
390
370
350
330
310
290
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
V IN (V)
Figure 28. P IN vs V IN
4 LEDs, 2.5 ≤ V DX ≤ 3.9V, I DX = 15mA
16
Product Folder Links: LM2794 LM2795
Copyright ? 2002–2013, Texas Instruments Incorporated
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