LM3915 IC数据表，PINOUT，应用程序电路

If you are having difficulty in understanding how to use an LM3915 IC, this article will help you to easily construct any desired applicable circuit using this IC. Here, we will discuss the datasheet of the IC LM3915, its pinout functions, its main electrical specifications, and also a few useful application circuits.

General Description

LM3915是一种单石IC，旨在感知模拟电压信号，并在其10个输出中产生增量或顺序逻辑开关。

Inidicating devices likes LEDs, LCD or vaccum displays can be attached with these outputs to obtain a corresponding visual indication in response to the varying input analogue signal.

The IC has one pinout for designating whether the output LEDs will sequence individually (dot mode) or in form of a bar graph.

可以连接LED而无需限制电阻，因为IC包括10个输出的内部可编程电流调节。

包括所有10个LED在内的IC电路可以使用低至3V电源和25V的最高运行。

IC具有适应性的电压参考和精确的10步电压分隔器。高阻抗输入缓冲区可以用从0V到 +1.5V以内的模拟电压馈送。

Further more, the inputs are well protected against signals upto the range of ±35V.

The input buffer runs 10 opamp comparators which are all referenced to the precision divider network. Accuracy level of the system is normally in the vicinity of 1 dB.

The LM3915’s 3 dB/step display is built for accepting input signals with broad dynamic range. For example the input can be in the form of audio or music signal, varying light intensity or vibrational electricity.

Audio applications could be in the form of average or peak level indicators, power meters and RF signal strength meters.

Upgrading traditional analoguevU meters with an LM3915based LED bar graph gives a better illuminated response, a durable display with improved field of vision enabling better interpretation of input signal.

LM3915非常易于使用。除了十个LED外，您甚至还可以使用只有一个电阻器的1.2V全尺寸远程示意电表。

另一个单独的电阻器设置了1.2V至12V之间的全尺寸范围，而不管电源电压值如何。LED的亮度很容易用一个外部锅控制。

Typical LM3915 Circuit Configuration

下图显示了如何以最典型或基本的功能模式设置IC LM3915。

If you are a new hobbyists and want to configure the pinouts of IC LM3915 or LM3914 quickly to get the required actions, then the following diagram could be used. The pinout details are explained below:

pin#10, pin#11, pin#12, pin#13, pin#14, pin#15, pin#16, pin#17, pin#18, and pin#1 = All are outputs for LED connection. LEDs do not need an external resistance, but preferably the LED supply line must be restricted to 5V to keep the dissipation on the lower side.

Pin#3 is the VDD or the positive supply input for the IC, which can take any supply between 3V and 25V, but I recommend using 5V to keep the LED dissipation on the lower side.

Pin#8 is the Vss or the ground (negative) supply pin of the IC.

引脚＃6和引脚＃7可以通过1K电阻连接在一起，并终止于接地线。

销钉＃5必须如上图中通过10K预设和电容器配置。可以根据输入信号的强度来调整此预设以设置全尺度LED照明范围。

销# 9可能是孤立的(打开)或connected to the +supply line. When left unconnected, the LEDs sequence up/down individually appearing like a running "DOT" and hence called the DOT mode. When pin#9 is connected to the positive line, the LED sequence like a up/down moving illuminated bar, hence called the bar mode.

完成此操作后，它只是为了馈送输入信号，并按照不同的输入信号或音乐振幅

绝对最大额定值

The absolute maximum rating of LM3915 indicates the maximum voltage and current parameters the device is permitted to handle.

• Supply Voltage = 25V
• Output Supply on the LEDs if you are using a separate supply here = 25V (same as above)
• 最大输入信号范围= +/- 35V
• 分隔引用电压= -100mv供应水平。
• 功率耗散= 1365 MW

IC的内部布局

下图显示了IC的内部布局。我们可以看到如何安排OPAM比较器以处理PIN＃5处的输入信号。引脚＃7的参考通过梯形类型电阻分隔网络在非转移输入上以增量顺序应用。

Functional Description

The above basic LM3915 block diagram provides the general perception of the circuit’s functioning. A high input impedance voltage follower buffer responds to the input pin#5 signals.

该引脚可抵抗过电压和反极性信号。然后，来自缓冲区的信号转到10个比较器组。

通过电阻器分隔串系列，每个操作阻尼都会偏向逐渐增加的参考水平。在上图中，电阻网络与内部1.25V参考电压链接。

Here, , for every 3 dB rise in the input signal, a switch in the comparator level is triggered causing the respective LED to move and sequence accordingly, interpreting the signal response.

该内部电阻分隔器可以通过外部电阻分隔网络在销钉＃5处的0-2伏的电势进行操作。

内部电压参考

IC LM3915的参考电压旨在可变，以便在REF OUT（引脚＃7）和Ref（引脚＃8）之间构建一个微小的1.25V。

The reference voltage is implemented across the resistor R1 which can be changed as per preference. Because we have a constant supply DC voltage, a constant current I1 is allowed to move through the output setting resistor R2 enabling an output voltage of:

v_OUT= V_REF（1 + R2/R1） + I_ADJR2

The current taken in by the reference voltage pin #7 decides the amount of LED current. We can expect around 10 times this current that may be permissible to be consumed by each illuminated output LED.

无论供应电压变化和温度变化如何，该电流或多或少是恒定的。在计算LED驱动器电流时，必须考虑内部10驱动器分隔线以及外部电流和电压设置分隔线的电流。

The IC provides a feature for modulating real time referenced LED brightness, or in response to input voltage variations and other signals. This allows inclusion of many innovative displays or options for producing input over-voltages, alarms, etc.

LM3915的输出都是内部控制的NPN BJT缓冲区，如下所示。

An internal feedback hook restricts the transistor from over current situations. Output current for the LEDs is fixed at roughly to 10 times the reference load current, irrespective of variations in the output voltage until of course the transistors are not saturated with high input supply.

如何使用模式引脚＃9

This pin is configured to enforce two functions. Please see the following simplified block diagram.

点或条模式选择

当引脚＃9连接到 +电源线（或在-100mv和电源级别之间）时，比较器C1感应到这一点，并在条形图模式下设置输出。在这种模式下，所有LED都以照明的“栏”响应，例如时尚，它会响应5号引脚的不同信号而向上移动。

如果引脚＃9未连接，则将输出设置为“点”模式。意味着LED一次单独/下一个单独的序列，产生脉动照明点或点（如外观）。

The basic way to configure pin #9 is either keep it open or unconnected for implementing dot mode or connect it to supply V+ for implementing the bar mode.

In bar mode operation, pin #9 should be hooked up straight away with pin #3. The LED + line that supplies large currents to the LED chain should not be used with pin #9 so that large IR drops is kept aloof from this pin.

To ensure that the output LED display works correctly when more than one LM3915s are cascaded in dot mode, special circuitry in built-in such that the LED at pin #10 shuts off for the first LM3915 IC at the momenet when LED #1 of the second LM3915 is switched ON.

The design for cascading LM3915 ICs together in dot mode can be witnessed below.

由于输入信号电压低于第二LM3915的阈值的条件，LED＃11停留被关闭。第一个LM3915的引脚＃9因此经历了有效的开路，该电路使IC以DOT模式运行。

However the moment the input signal crosses over the threshold of LED #11, pin #9 of the first LM3915 is dropped by a level equal to the LED's forward voltage (1.5V or more) below VLED.

比较器C2立即采取了这种情况，在下面参考了0.6 V VLED。它强迫C2输出速度低，关闭输出晶体管Q2，随后关闭LED＃10。

通过连接到销钉11的电阻20K检测到VLED。从LED＃9重定向的微小电流（低于100 µA）不会对LED强度产生任何可识别的影响。引脚＃1处的附加电流源保持至少100 µA，无论输入信号上升是否足以关闭LED。

This means that pin #9 of the first LM3915 is kept sufficiently low such that it keeps LED #10 shut off while any of the upper LEDs in the sequence is illuminated.

尽管100 µA通常不会产生相当大的LED亮度，但如果使用高效LED并且在整个黑暗中，它可能会足够可见。如果这听起来不可接受，那么简单的补救措施将是用10k电阻器分流为11。

1V IR下降高于关闭LED＃10所需的最低900 mV，但足够小，确保LED＃11不会超过不良的限制。

当大量的LED电流碰巧被消耗时，特别是在条形图模式下，就会出现最具挑战性的问题。

Such currents moving away from the ground pin lead to voltage drops within outer wiring, causing glitches and fluctuations.

Getting the returning cables from signal ports, ground references and from bottom-side of the resistor chain to a single common terminal that may be closest to pin #2 becomes an ideal approach.

从VLED到公共LED阳极的扩展电线连接可能会触发振荡。根据该问题的严重程度是0.05 µF至2.2 µF解耦电容器，可以在LED阳极公共和引脚＃2之间使用。

这有助于抑制任何发达的振荡。如果LED阳极供应线接线是无法实现的，则跨引脚1到PIN＃2的脱钩相同，就足以取消干扰。

功耗

需要考虑耗能，特别是在条模式下。例如，有5V电源和所有LED设置以与20 MA电流一起工作，因此IC的LED驱动器部分预计将消散超过600兆瓦。

In cases like this a 7.5Ω resistor can be used in series with the LED supply line, which might help to bring down the dissipation level to half the original value. The negative end of this resistor must be reinforced with a 2.2 µF solid tantalum bypass capacitor with pin #2.

CASCADING LM3915 ICs

For using display signals of 60 dB or 90 dB dynamic range, you may require a few LM3915 ICs to be cascaded together.

级联几个LM3915s的一种直接，负担得起的方法是固定两个ICS 30 dB的参考电压，如图所示。

Potentiometer R1 is employed to regulate the full scale voltage of the first LM3915 IC to 316 mV marginally while the second IC’s reference is scheduled at 10V by R4.

The disadvantage of this technique is that the switch ON threshold of LED #1 is merely 14 mV and, considering that the LM3915 may have an offset voltage of up to 10 mV, substantial errors can take place.

绝对不建议使用60 dB显示，需要在少数初始显示阈值下进行体面的精度。

A superior technique shown in the below figure keeps the reference at 10V for each of the two LM3915 ICs and boosts the input signal to the lower LM3915 by 30 dB. Given that a pair of 1% resistors are able to fix the amplifier gain at ±0.2 dB, the need for a gain reduction becomes unnecessary.

但是，5 mV的OPAMP偏移电压可能能够将第一个LED开关限制更改约4 dB，因此需要修整。

请记住，只有一个调整可能有助于使两者之间的偏移以及30 dB增益阶段以及30 dB增益阶段的偏移无效。

另一方面，可以将合理高振幅的输入信号直接提供给LM3915，并随后被30 dB衰减以推动第二个LM3915 IC。

LM3915申请电路

半波峰探测器

通过IC LM3915展示AC信号的最佳方法是将其直接实施至引脚5未经启动。由于LED照明表示所施加的AC波形的瞬时幅度，因此可以在相同方法中确定音频信号的最大值和平均值。

LM3915特别针对正期为正的半循环，但不会损害任何输入信号±35V（如果使用39K电阻器和输入信号），则不会损害任何输入信号（甚至最高至±100V）。

建议您以DOT模式操作电路，并允许每个LED绘制30mA，以便从设置中获得最佳的亮度。

In order to detect mean value of the AC or for peak detection, rectification of the signal will be required.

如果设置LM3915在其电压分隔器上具有10V的全尺度，则第一LED的开关阈值仅为450 mV。由于0.6 V二极管阈值，普通的硅二极管整流器可能无法在较低级别上有效工作。

The half-wave peak detector in the above Figure employs a PNP emitter-follower ahead of the diode. Due to the fact that the transistor’s base-emitter voltage blocks the diode offset in the range of around 100 mV, the method works good enough with single LM3915 applications using a 30 dB display.

More Application Circuits

There are actually a huge number of circuit applications which you can build using the IC LM3915. I have already discussed a a handful of them in this website, which you can refer by visiting这里：

因此，这是一个简短的描述，解释了IC LM3915的数据表和引脚详细信息。如果您还有其他疑问，请通过下面的评论框告诉我们，我们将尽早与我们联系。

参考文献

https://www.digchip.com/datasheets/download_datasheet.php?id=514550&part-number=lm3915

https://es.wikipedia.org/wiki/LM3915