LM3914 Dot/Bar Display Driver

27 September 2018 - 0 Comments

LM3914 Dot/Bar Display Driver

LM3914 PINOUT

LM3914 Pin Configuration

Pin Number	Pin Name	Description
1 and 10 to 18	LED1, LED2, LED3.....LED10	必须控制的10个LED连接到这些销钉
2	V- / Ground	Ground pin of the IC
3	V+ / VCC	Supply Voltage (3-18)V
4	RLO	Low level voltage for potential divider
5	Signal	Analog signal Input pin based on which the LED is controlled.
6	Rhi	潜在分隔线的高水平电压
7	REF OUT	Output Reference Voltage for LED current limiting
8	REF ADJ	调整销钉以进行电压参考
9	模式	Select between Dot/Bar Mode

Specifications

模拟控制的LED驱动器IC
Number of controllable LEDs: 10
操作电压：3V至18V
输入模拟电压范围：1.2V至12V
LED sink current: 2mA to 30mA (programmable)
Both Dot/Bar mode available
Can be cascaded to control upto 100 LEDs
有18针蘸酱，PLCC包装

Note:Complete Technical Details can be found in theLM3914数据表given at the end of this page.

等效的LED驱动器

LM3916

Alternative LED Driver IC’s

CD4511,MAX7219，CD4054

Where to use LM3914?

LM3914是一个模拟控制的LED driver IC, meaning it can control (turn on or off) 10 LED lights based on an analog input voltage. This IC eliminates the need for microcontroller and programming and also reduces the hardware required to control 10 LEDs.

The analog input voltage can vary from 3V to 18V and the LED current can be limited by simply using a single resistor on pin 7 (Ref Out). The IC also has two operating modesDOT mode和条模式, also more than one IC can be cascaded to control upto 100 LEDs. Since the LEDs can be controlled without any flickering and flawlessly with equal brightness these IC’s are commonly used in visual alarms and other metering/monitoring applications. So, if you are looking for an IC to driver your bar LED lights or other sequence of 10 LED then this IC might be of interest to you.

How to use a LM3914?

The advantage of using LM3914 is that it requires minimum hardware and can be easily set up. We simply have to connect the 10 LEDs to the IC, set the reference voltages for input voltage and limit the current through the LED and we are all set. The below circuit is a typicalLM3914的应用电路.

LM3914 DotBar LED Display Driver Working

Simply power the IC using the V+ and V- and the analog signal voltage is given to pin 5. Here we have used 9V to power the IC to monitor an analogy voltage of 0-5V. Always note that the voltage used to power the IC (here 9V) should be at least 1.5V more that the monitoring voltage(here 5V).

Since we are monitoring 0-5V here, the low reference voltage (pin 4) is set at 0V and the high reference voltage (pin 6) is set to 5V. As you might have noticed we have connected all the 10 LEDs directly to the IC without any current limiting resistor this is because the IC has an internal current limiter and the value of current can be set by using the pin VRO (pin 7). The formulae to calculate the current is given below, where I is the current through each LED and RL is the resistor connected to pin 7.

i = 12.5/rl

在上面的示例中，我们使用了470欧姆电阻作为RL，因此通过每个LED的电流约为25mA，您可以根据需要修改值。另请注意，LED的阴极连接到IC，并连接到 +5V。这是因为IC输出引脚只能下沉电流并且无法采购。

The IC can operate in two different modes, one is the dot mode and the other is bar mode. In dot mode the mode pin (pin 9) has to be left floating, in this mode only one LED will be turned on based on the input voltage. In Bar mode the mode pin (pin 9) has to be connected to V+ and in this mode the LED will turn on or turn off sequentially based on the input voltage. Both the modes are shown in the gif file above.