0.28-inch Quadruple Digit Seven-Segment LED Display Datasheet - Digit Height 7mm - Super Red Color - English Technical Document

1. Product Overview

This document details the specifications for a 0.28-inch (7 mm) digit height, quadruple-digit, seven-segment LED display. The device is designed for applications requiring clear, bright numeric readouts with excellent visibility. It utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for its light-emitting elements, specifically engineered to produce a super red color output. The display features a gray face and white segments, which contributes to high contrast and superior character appearance under various lighting conditions.

The core design philosophy focuses on providing a reliable, solid-state solution with low power requirements, making it suitable for a wide range of consumer, industrial, and instrumentation products where numeric data presentation is critical.

2. Key Features and Advantages

The display incorporates several design features that enhance its performance and usability:

• Digit Height: 0.28 inches (7.0 mm), offering a balanced size for good readability without excessive panel space consumption.
• Segment Design: Continuous uniform segments ensure consistent illumination and a professional, clean character appearance.
• Optical Performance: Delivers high brightness and high contrast, facilitated by the AlInGaP chips and the gray face/white segment design.
• Viewing Angle: A wide viewing angle ensures the display remains legible from various positions relative to the user.
• Low Power Operation: Engineered for efficient light output relative to input power, suitable for battery-powered or energy-conscious applications.
• Reliability: As a solid-state device, it offers high reliability and long operational life compared to mechanical displays.
• Binning: The luminous intensity is categorized (binned), allowing for consistency in brightness across multiple units in a production run.

3. Technical Specifications Deep Dive

3.1 Electrical and Optical Characteristics

The performance of the display is defined under standard test conditions at an ambient temperature (T_A) of 25°C. Key parameters include:

• Average Luminous Intensity (I_V): Ranges from a minimum of 200 µcd to a typical 600 µcd when driven at a forward current (I_F) of 1 mA per segment. This parameter is measured using a sensor filtered to approximate the CIE photopic eye-response curve.
• Peak Emission Wavelength (λ_p): Typically 639 nm, defining the primary color point of the super red emission.
• Spectral Line Half-Width (Δλ): Approximately 20 nm, indicating the spectral purity of the emitted light.
• Dominant Wavelength (λ_d): Typically 631 nm, another key metric for specifying the perceived color.
• Forward Voltage per Segment (V_F): Typically 2.6 V with a maximum of 2.6 V at I_F = 20 mA. This is crucial for designing the driving circuitry.
• Reverse Current per Segment (I_R): Maximum of 100 µA when a reverse voltage (V_R) of 5 V is applied.
• Luminous Intensity Matching Ratio (I_V-m): A ratio of 2:1 maximum, ensuring reasonable uniformity in brightness between different segments of the same digit or across digits.

3.2 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation outside these limits is not advised.

• Power Dissipation per Segment: 70 mW maximum.
• Peak Forward Current per Segment: 90 mA maximum under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width).
• Continuous Forward Current per Segment: 25 mA maximum at 25°C. This rating derates linearly at 0.33 mA/°C as temperature increases.
• Reverse Voltage per Segment: 5 V maximum.
• Operating Temperature Range: -35°C to +85°C.
• Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: The device can withstand a soldering temperature of 260°C for 3 seconds at a distance of 1/16 inch (approximately 1.6 mm) below the seating plane.

4. Mechanical and Package Information

The device comes in a standard LED display package. The provided dimensional drawing specifies the exact physical footprint, including the spacing between digits, overall height, width, depth, and the position and diameter of the pins. All dimensions are provided in millimeters with a standard tolerance of ±0.25 mm unless otherwise noted. This information is critical for PCB (Printed Circuit Board) layout and mechanical integration into the end product's enclosure.

5. Pin Configuration and Internal Circuit

The display has a 16-pin configuration. It is configured as a multiplex common cathode type. This means each digit's cathode is connected separately, while the anodes for corresponding segments (e.g., all 'A' segments) are connected together across digits. This architecture allows for multiplexing, where digits are illuminated one at a time in rapid succession, reducing the total number of required driver pins and overall power consumption.

The pinout is as follows:

• Pin 1: Common Cathode (Digit 1)
• Pin 2: Anode for segment C and L3
• Pin 3: Anode for Decimal Point (D.P.)
• Pin 5: Anode for segment E
• Pin 6: Anode for segment D
• Pin 7: Anode for segment G
• Pin 8: Common Cathode (Digit 4)
• Pin 11: Common Cathode (Digit 3)
• Pin 12: Common Cathode for indicators L1, L2, L3
• Pin 13: Anode for segment A and L1
• Pin 14: Common Cathode (Digit 2)
• Pin 15: Anode for segment B and L2
• Pin 16: Anode for segment F
• Pins 4, 9, 10 are noted as "No Connection" or "No Pin".

An internal circuit diagram typically shows the interconnection of the LED chips for each segment and digit, clarifying the multiplexed common cathode structure.

6. Binning System Explanation

The datasheet indicates that the devices are "Categorized for Luminous Intensity." This refers to a binning or sorting process based on measured light output. During manufacturing, slight variations occur. By testing and grouping units into specific intensity bins (e.g., a range of µcd values), manufacturers and designers can ensure that all displays used in a single product or production batch have very similar brightness levels. This prevents noticeable variations in display intensity between units, which is essential for product quality and user experience. Designers should specify the required bin when ordering to guarantee consistency.

7. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristic Curves." While the specific graphs are not detailed in the text, such curves typically included in full datasheets are vital for design:

• Forward Current (I_F) vs. Forward Voltage (V_F): This IV curve shows the nonlinear relationship, helping to determine the appropriate current-limiting resistor or constant-current driver setting for a given supply voltage.
• Luminous Intensity (I_V) vs. Forward Current (I_F): This curve shows how light output increases with current, often in a sub-linear fashion at higher currents, informing decisions on drive current for desired brightness vs. efficiency.
• Luminous Intensity vs. Ambient Temperature: Shows how light output decreases as the junction temperature of the LED increases. This is critical for applications operating in high-temperature environments.
• Spectral Distribution: A graph of relative intensity vs. wavelength, visually confirming the peak (639 nm) and half-width (20 nm) specifications.

8. Soldering and Assembly Guidelines

Based on the Absolute Maximum Ratings, the device can withstand wave or reflow soldering processes. The key parameter specified is the solder temperature profile: 260°C for 3 seconds at a point 1/16 inch (1.6 mm) below the seating plane. This aligns with common lead-free soldering profiles. Designers and assemblers must ensure their soldering processes do not exceed this thermal stress to prevent damage to the internal wire bonds or the LED chips themselves. Standard ESD (Electrostatic Discharge) precautions should be observed during handling.

9. Application Suggestions and Design Considerations

9.1 Typical Application Scenarios

This display is well-suited for any device requiring a clear, reliable numeric readout:

• Test and Measurement Equipment: Multimeters, oscilloscopes, power supplies, frequency counters.
• Industrial Controls: Panel meters, process indicators, timer displays, counter displays.
• Consumer Electronics: Audio equipment (amplifiers, receivers), kitchen appliances, clocks.
• Automotive Aftermarket: Gauges and diagnostic tools (where environmental specs are suitable).
• Medical Devices: Patient monitors, diagnostic equipment (subject to additional regulatory requirements).

9.2 Design Considerations

• Drive Circuitry: Must implement multiplexing for the common cathode digits. This requires a microcontroller or dedicated driver IC capable of sequentially sinking current for each digit's cathode while sourcing current to the appropriate segment anodes. Proper current limiting (via resistors or constant-current drivers) is essential based on the V_F and desired I_F.
• Brightness Control: Brightness can be controlled by adjusting the peak forward current (within ratings) or, more commonly in multiplexed designs, by varying the duty cycle of the multiplexing signal (PWM).
• Viewing Angle: The wide viewing angle is an advantage, but the mechanical design should still consider the primary user's sight lines.
• Thermal Management: While low power, continuous operation at high ambient temperatures near the maximum rating may require derating the forward current as specified (0.33 mA/°C above 25°C) to maintain reliability and prevent accelerated lumen depreciation.

10. Technical Comparison and Differentiation

The primary differentiator of this display is the use of AlInGaP technology for the super red color. Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) red LEDs, AlInGaP offers significantly higher luminous efficiency, resulting in greater brightness for the same input current, or equivalent brightness at lower power. It also generally provides better temperature stability and color purity. The gray face with white segments is a specific design choice to maximize contrast, which may offer an advantage over all-red or all-green displays in high-ambient-light conditions.

11. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the "No Connection" pins?
A: They are physically present pins that are not electrically connected to any internal element. They may be used for mechanical stability during soldering or to fit a standard package footprint. They must not be used for electrical connections.

Q: How do I calculate the current-limiting resistor for a segment?
A: Use Ohm's Law: R = (V_supply - V_F) / I_F. For a 5V supply, typical V_F of 2.6V, and desired I_F of 20 mA: R = (5 - 2.6) / 0.02 = 120 Ω. Always use the maximum V_F from the datasheet for a conservative design to avoid overcurrent.

Q: Can I drive this display without multiplexing?
A: Direct drive (static drive) is theoretically possible by individually addressing each segment of each digit, but it would require a very high number of I/O pins (4 digits * 7 segments + decimal + indicators = over 30 pins) and is highly inefficient. Multiplexing is the intended and practical method.

Q: What does "Luminous Intensity Matching Ratio 2:1" mean?
A> It means the measured luminous intensity of any one segment or digit will not be more than twice the intensity of any other segment or digit under the same test conditions. It defines the maximum allowable variation within a device.

12. Operational Principle

A seven-segment display is composed of seven rectangular LED segments (labeled A through G) arranged in a figure '8' pattern, plus an additional circular LED for a decimal point (DP). By selectively illuminating specific combinations of these segments, all decimal digits (0-9) and some letters can be formed. In a multiplexed common cathode design like this one, all the anodes for a given segment type across all digits are connected together (e.g., all 'A' segment anodes). Each digit has its own separate cathode connection. To display a number, the microcontroller activates (sets high) the anode lines corresponding to the segments needed for that digit and simultaneously activates (sets low/sinks current) the cathode line for that specific digit. It holds this for a short period (e.g., 1-5 ms), then moves to the next digit, cycling through all digits rapidly. The human eye's persistence of vision blends these rapid pulses into a stable, seemingly continuously lit multi-digit number.

13. Industry Trends and Context

While seven-segment LED displays remain a robust, cost-effective, and highly reliable solution for numeric readouts, the industry has seen a parallel growth in alternative technologies. Dot-matrix OLED and LCD displays offer far greater flexibility for displaying alphanumeric characters, symbols, and even simple graphics. However, for applications where only numbers need to be displayed with utmost clarity, brightness, wide viewing angle, and simplicity of interface, LED seven-segment displays like this one continue to be a preferred choice. The trend within this segment is towards higher efficiency materials (like AlInGaP replacing older ones), lower operating voltages, smaller package sizes for higher density, and integrated driver circuitry to simplify design. The device described here represents a mature and optimized implementation of this enduring technology.