How to understand the datasheet

Here is a guide to the professional vocabulary and concepts related to LED digital tubes (LED segment displays) in English. This will help you read datasheets, communicate with engineers, or write technical specifications.

1. Core Terminology 

• LED Segment Display / LED Digital Tube: The general term for these components.

• 7-Segment Display: The most common type, used to display numbers (0-9) and some basic letters.

• 14-Segment / 16-Segment Display (Alphanumeric Display): Used to display the full alphabet (A-Z) and numbers more clearly.

• Digit: Refers to a single numeric character.

  • Examples: 1-digit (single digit), 2-digit (dual digit), 4-digit (quad digit).

2. Structural & Pin Configurations

Understanding how the internal LEDs are connected is crucial for circuit design.

• Common Cathode (CC): All the negative terminals (cathodes) of the segments are connected together to a common ground (GND). You light up a segment by applying a high voltage (logic high) to its individual pin.

• Common Anode (CA): All the positive terminals (anodes) of the segments are connected together to a common power supply ($V_{CC}$). You light up a segment by pulling its individual pin to ground (logic low).

• Pinout / Pin Configuration: The specific layout and assignment of the physical pins on the display.

• Decimal Point (DP): The extra dot used for displaying decimal numbers.

3. Segment Naming Conventions 

Standard 7-segment displays use a standard lettering system from a to g (plus DP).

• Segment A to G: The standard labels for the seven main lighting elements.

  • Layout: a (top), b (top right), c (bottom right), d (bottom), e (bottom left), f (top left), g (middle).

4. Driving Methods & Control 

• Static Drive : Each segment of each digit is driven by a dedicated I/O pin or driver. It offers maximum brightness but requires many pins.

• Dynamic Drive / Multiplexing: The digits share the same segment lines (a-g) but have separate common pins. The microcontroller flashes each digit one by one very rapidly.

• Refresh Rate: The speed at which the display cycles through the digits in a dynamic drive setup (measured in Hz). If it's too low, it causes flickering.

• Ghosting: A common issue in dynamic driving where a faint image of a digit appears on the adjacent digit due to slow switching speeds.

5. Electrical & Optical Characteristics

These are terms you will find directly on a technical datasheet.

• Forward Voltage (VF): The voltage required across the LED segment to make it light up (typically 1.8V–2.2V for red, 3.0V–3.4V for blue/white).

• Forward Current (IF): The current flowing through the segment (usually 10mA–20mA for standard brightness).

• Luminous Intensity: The perceived brightness of the display, usually measured in millicandela (mcd).

• Peak Wavelength (λp): The specific wavelength of light emitted, determining the exact color (e.g., 635nm for high-efficiency red).

• Power Dissipation: The maximum amount of power the display can safely dissipate without burning out.