The LM3914 is a monolithic integrated circuit that senses analog voltage levels and drives 10 LEDs, providing a linear analog display. A single pin changes the display from a moving dot to a bar graph. The current drive to the LEDs is regulated and programmable, eliminating the need for resistors. This feature is one that allows the operation of the whole system from less than 3V. The circuit contains its own adjustable reference and accurate 10-step voltage divider. The low-bias-current input buffer accepts signals down to the ground, or V−, yet needs no protection against inputs of 35V above or below ground.
The buffer drives 10 individual comparators referenced to the precision divider. Indication non-linearity can thus be held typically to 1⁄2%, even over a wide temperature range. A 1.2V full-scale meter requires only 1 resistor and a single 3V to 15V supply in addition to the 10 display LEDs. If the 1 resistor is a pot, it becomes the LED brightness control. The simplified block diagram illustrates this extremely simple external circuitry. When in the dot mode, there is a small amount of overlap or “fade” (about 1 mV) between segments. This assures that at no time will all LEDs be “OFF”, and thus any ambiguous display is avoided. Various novel displays are possible.
LM3914 Pinout
LM3914 Pin Configuration
| Pin No | Pin Name | Description |
|---|---|---|
| 1 | LED NO 1 | Led No 1 |
| 2 | V- | -ve Voltage Pin |
| 3 | V+ | +ve Voltage Pin |
| 4 | DIVIDER (LOW END) | Divider (Low End) |
| 5 | SIGNAL INPUT | Signal Input Pin |
| 6 | DIVIDER (HIGH END) | Divider(High End) |
| 7 | REFERENCE OUTPUT | Reference Output Pin |
| 8 | REFERENCE ADJUST | Reference Adjust Pin |
| 9 | MODE SELECT | Mode Select Pin |
| 10 | LED NO. 10 | Led No10 Pin |
| 11 | LED NO. 9 | Led No 9 Pin |
| 12 | LED NO. 8 | Led No 8 Pin |
| 13 | LED NO. 7 | Led No 7 Pin |
| 14 | LED NO. 6 | Led No 6 Pin |
| 15 | LED NO. 5 | Led No 5 Pin |
| 16 | LED NO. 4 | Led No 4 Pin |
| 17 | LED NO. 3 | Led No 3 Pin |
| 18 | LED NO. 2 | Led No 2 Pin |
LM3914 Features
- Drives LEDs, LCDs or vacuum fluorescents
- Bar or dot display mode externally selectable by user
- Expandable to displays of 100 steps
- Internal voltage reference from 1.2V to 12V
- Operates with single supply of less than 3V
- Inputs operate down to ground
- Output current programmable from 2 mA to 30 mA
- No multiplex switching or interaction between outputs
- Input withstands ±35V without damage or false outputs
- LED driver outputs are current regulated, open-collectors
- Outputs can interface with TTL or CMOS logic
- The internal 10-step divider is floating and can be referenced to a wide range of voltages
Application
- Illustrates adjusting of the reference to a desired value
- Proper grounding for accurate operation
- Avoiding oscillations
You can download this datasheet for LM3914 Bar-Graph Display Driver – Datasheet from the link given below:
