參數(shù)資料
型號(hào)： LM3915
廠商： National Semiconductor Corporation
英文描述： Dot/Bar Display Driver
中文描述： 點(diǎn)/酒吧顯示驅(qū)動(dòng)程序
文件頁(yè)數(shù)： 11/24頁(yè)
文件大小： 602K
代理商： LM3915
Application Hints
(Continued)
To extend this approach to get a 90 dB display, another
30 dB of amplification must be placed in the signal path
ahead of the lowest LM3915. Extreme care is required as the
lowest LM3915 displays input signals down to 0.5 mV! Sev-
eral offset nulls may be required. High currents should not
share the same path as the low level signal. Also power line
wiring should be kept away from signal lines.
TIPS ON REFERENCE VOLTAGE
AND LED CURRENT PROGRAMMING
SINGLE LM3915
The equations in Figure 7 illustrate how to choose resistor
values to set reference voltage for the simple case where no
LED intensity adjustment is required.ALED current of 10 mA
to 20 mA generally produces adequate illumination. Having
10V full-scale across the internal voltage divider gives best
accuracy by keeping signal level high relative to the offset
voltage of the internal comparators. However, this causes
450 μA to flow from pin 7 into the divider which means that
the LED current will be at least 5 mA. R1 will typically be be-
tween 1 k
and 2 k
. To trim the reference voltage, vary R2.
The circuit in Figure 8shows how to add a LED intensity con-
trol which can vary LED current from 9 mAto 28 mA. The ref-
erence adjustment has some effect on LED intensity but the
reverse is not true.
MULTIPLE LM3915s
Figure 9 shows how to obtain a common reference trim and
intensity control for two LM3915s. The two ICs may be con-
nected in cascade for a 60 dB display or may be handling
separate channels for stereo. This technique can be ex-
tended for larger numbers of LM3915s by varying the values
of R1, R2 and R3 in inverse proportion to the number of de-
vices tied in. The ICs’ internal references track within
100 mV so that worst case error from chip to chip is only
0.1 dB for V
REF
= 10V.
DS005104-13
FIGURE 5. Low Cost Circuit for 60 dB Display
DS005104-14
FIGURE 6. Improved Circuit for 60 dB Display
L
www.national.com
11
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM3915J/A+ 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LED Display Driver
LM3915N 制造商:Texas Instruments 功能描述: 制造商:Texas Instruments 功能描述:IC LED DISPLAY DRIVER 3915 DIP18
LM3915N/A+ 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LED Display Driver
LM3915N/B+ 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LED Display Driver
LM3915N-1 功能描述:LED照明驅(qū)動(dòng)器 RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N
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