LTD-5023AJR 0.56-inch AlInGaP Super Red LED Display Datasheet - Digit Height 14.22mm - Forward Voltage 2.6V - Power Dissipation 70mW - English Technical Document

1. Product Overview

The LTD-5023AJR is a high-performance, low-power seven-segment LED display module. Its primary function is to provide clear, bright numeric and limited alphanumeric character output for electronic devices requiring a digital readout. The core technology is based on AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material, specifically engineered to produce a super red color with high efficiency and reliability.

The device is categorized as a common cathode type, meaning all the cathodes of the LEDs for each digit are connected together internally. This configuration simplifies driving circuitry, particularly for multiplexed applications. It features a right-hand decimal point per digit, allowing for flexible numerical representation. The display is characterized by its solid-state construction, offering advantages over older technologies like vacuum fluorescent or incandescent displays in terms of shock resistance, lifespan, and power efficiency.

2. Technical Specifications Deep Dive

2.1 Photometric and Optical Characteristics

The optical performance is central to this display's functionality. The primary color is defined as \"super red,\" achieved through AlInGaP chips. Key optical parameters measured at an ambient temperature of 25\u00b0C include:

• Average Luminous Intensity (I_V): Ranges from a minimum of 320 \u00b5cd to a typical maximum of 700 \u00b5cd when driven at a very low forward current (I_F) of 1mA per segment. This high brightness at low current is a significant feature.
• Peak Emission Wavelength (\u03bb_p): Typically 639 nanometers (nm). This defines the specific point of highest intensity in the emitted light spectrum.
• Dominant Wavelength (\u03bb_d): Typically 631 nm. This is the wavelength perceived by the human eye and is crucial for color specification.
• Spectral Line Half-Width (\u0394\u03bb): Approximately 20 nm. This parameter indicates the spectral purity or the narrowness of the emitted light band.
• Luminous Intensity Matching Ratio (I_V-m): Maximum of 2:1 at I_F=1mA. This ensures uniformity in brightness between different segments of the same digit, critical for a consistent visual appearance.

All luminous intensity measurements are performed using a sensor and filter combination calibrated to the CIE photopic eye-response curve, ensuring data relevance to human vision.

2.2 Electrical and Absolute Maximum Ratings

Adherence to these ratings is essential for reliable operation and preventing permanent damage to the device.

• Continuous Forward Current per Segment: Absolute maximum is 25 mA. A linear derating factor of 0.33 mA/\u00b0C is applied for ambient temperatures (T_A) above 25\u00b0C.
• Peak Forward Current per Segment: Maximum of 90 mA, but only under pulsed conditions with a 1/10 duty cycle and a pulse width of 0.1ms. This allows for brief over-driving to achieve higher peak brightness in multiplexed systems.
• Power Dissipation per Segment: Maximum of 70 mW. This limit, combined with the forward current rating, dictates the maximum permissible forward voltage under operating conditions.
• Reverse Voltage per Segment: Maximum of 5 Volts. Exceeding this can damage the LED junction.
• Forward Voltage per Segment (V_F): Typically 2.6V, with a maximum of 2.6V at a test current (I_F) of 20mA. The minimum is listed as 2V.
• Reverse Current per Segment (I_R): Maximum of 100 \u00b5A when a reverse voltage (V_R) of 5V is applied.

2.3 Thermal and Environmental Specifications

• Operating Temperature Range: -35\u00b0C to +85\u00b0C. This wide range makes the display suitable for various environmental conditions, from industrial controls to consumer electronics.
• Storage Temperature Range: -35\u00b0C to +85\u00b0C.
• Soldering Temperature: The device can withstand a solder temperature of 260\u00b0C for 3 seconds, measured 1/16 inch (approximately 1.6mm) below the seating plane. This is compatible with standard lead-free reflow soldering processes.

3. Binning and Categorization System

The datasheet explicitly states that the device is \"categorized for luminous intensity.\" This indicates a production binning process where displays are sorted based on their measured light output at a standard test current (likely 1mA or 20mA). Bins are defined by minimum and/or typical intensity values (e.g., the 320-700 \u00b5cd range). This allows designers to select parts with consistent brightness levels for their application, ensuring uniform appearance across multiple units in a product. While not detailed in this specific sheet, similar devices often have bins for forward voltage (V_F) and dominant wavelength (\u03bb_d) to guarantee electrical and color consistency.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical/Optical Characteristic Curves.\" Although the specific graphs are not provided in the text, standard curves for such a device would typically include:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the exponential relationship, crucial for designing current-limiting circuitry. The knee voltage is around the typical V_F of 2.6V.
• Luminous Intensity vs. Forward Current (I-L Curve): Demonstrates how light output increases with current, usually in a near-linear relationship within the operating range. It highlights the high efficiency at low currents (1mA).
• Luminous Intensity vs. Ambient Temperature: Shows the decrease in light output as junction temperature rises, important for high-temperature or high-power applications.
• Spectral Distribution Curve: A plot of relative intensity versus wavelength, centering around the 631-639 nm region with the specified 20 nm half-width.

5. Mechanical and Package Information

5.1 Physical Dimensions

The display features a digit height of 0.56 inches (14.22 mm). The package dimensions drawing is referenced, specifying all measurements in millimeters with a standard tolerance of \u00b10.25mm unless otherwise noted. The physical package houses two complete seven-segment digits plus their respective decimal points.

5.2 Pin Connection and Internal Circuit

The device has an 18-pin configuration. The pinout is clearly defined:

• Pins 1-12, 15-18: Anode connections for individual segments (A-G, DP) for Digit 1 and Digit 2.
• Pins 13 and 14: Common Cathode for Digit 2 and Digit 1, respectively.

The internal circuit diagram shows the common cathode arrangement: all LEDs for a given digit share a common cathode pin, while each segment (and the decimal point) has its own independent anode pin. This is the standard configuration for a common cathode, multi-digit display.

6. Soldering and Assembly Guidelines

The key assembly specification provided is the soldering profile: 260\u00b0C for 3 seconds at a point 1.6mm below the seating plane. This aligns with IPC/JEDEC standards for surface-mount device reflow soldering. Best practices include:

• Using a controlled reflow oven with a profile that ramps up to and cools down from the peak temperature appropriately to minimize thermal stress.
• Avoiding hand soldering directly to the LED package to prevent overheating and damaging the semiconductor chips or the plastic lens.
• Ensuring the display is stored in a dry environment prior to assembly to prevent moisture absorption, which can cause \"popcorning\" during reflow.

7. Application Suggestions

7.1 Typical Application Scenarios

This display is ideal for applications requiring clear, low-power numeric readouts:

• Test and Measurement Equipment: Multimeters, frequency counters, power supplies.
• Industrial Controls: Panel meters, process indicators, timer displays.
• Consumer Electronics: Audio equipment (amplifiers, receivers), kitchen appliances, clocks.
• Automotive Aftermarket: Gauges and diagnostic tools (where environmental specs are suitable).

7.2 Design Considerations

• Current Limiting: LEDs are current-driven devices. Each anode pin must be driven through a series current-limiting resistor. The resistor value is calculated as R = (V_supply - V_F) / I_F. Using the typical V_F of 2.6V and a desired I_F of 5-10mA for good brightness is common.
• Multiplexing: For multi-digit displays, multiplexing is used to control many segments with fewer driver pins. This involves rapidly cycling power between the common cathode of each digit while lighting the corresponding segments. The LTD-5023AJR's common cathode design is perfect for this. The peak current rating (90mA) allows for higher instantaneous currents during the short multiplexing pulse to achieve an average brightness comparable to a lower continuous current.
• Microcontroller Interface: Typically requires GPIO pins or a dedicated LED driver IC (like a shift register or constant current driver) to control the anodes and a transistor (NPN or N-channel MOSFET) to sink current from each common cathode pin during multiplexing.
• Viewing Angle: The datasheet mentions a \"wide viewing angle,\" which is beneficial for applications where the display may be viewed from off-axis positions.

8. Technical Comparison and Differentiation

The LTD-5023AJR differentiates itself through several key features:

• AlInGaP Technology: Compared to older GaAsP or GaP LEDs, AlInGaP offers significantly higher luminous efficiency, especially in the red/orange/amber spectrum, resulting in brighter output at lower currents.
• Low Current Operation: The explicit testing and selection for excellent low-current characteristics (down to 1mA/segment) make it superior for battery-powered or energy-sensitive applications where every milliamp counts.
• Segment Matching: The guarantee of a luminous intensity matching ratio (2:1 max) ensures visual consistency, which is not always a given with lower-grade displays.
• Contrast: The combination of a light gray face and white segment color, along with high brightness, contributes to excellent character appearance and high contrast for easy readability.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display directly from a 5V microcontroller pin?
A: No. You must use a current-limiting resistor in series with each anode. For a 5V supply and a target current of 10mA, the resistor would be approximately (5V - 2.6V) / 0.01A = 240 Ohms.

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength is the physical point of highest energy output from the LED. Dominant wavelength is the single-wavelength perception of the color by the human eye, which can differ slightly. Both are provided for complete optical specification.

Q: How do I use the two digits independently?
A: You control them via their separate common cathode pins (Pin 14 for Digit 1, Pin 13 for Digit 2). By turning one cathode low (ground) while keeping the other high (disconnected), you can select which digit is active. Then, apply voltage to the anode pins for the segments you wish to illuminate on that digit.

Q: Is this display suitable for outdoor use?
A: The operating temperature range (-35\u00b0C to +85\u00b0C) is quite robust. However, the datasheet does not specify an Ingress Protection (IP) rating against dust and water. For outdoor use, it would likely require an additional protective cover or enclosure.

10. Practical Design and Usage Example

Scenario: Designing a simple 2-digit voltmeter readout using a microcontroller.

1. Hardware Connection: Connect the 18 pins of the display to the microcontroller system. The two common cathode pins (13, 14) are connected to two NPN transistors (e.g., 2N3904), with the transistor collectors to the cathodes, emitters to ground, and bases to microcontroller GPIO pins via base resistors. The 16 anode pins (for segments A-G and DP of both digits) are connected to 16 GPIO pins of the microcontroller, each via a 220-330 Ohm current-limiting resistor.
2. Software Logic (Multiplexing): The firmware runs a timer interrupt every few milliseconds. In the interrupt service routine:
   • Turn OFF both cathode-driving transistors (set GPIOs high).
   • Set the GPIOs for the anode pins corresponding to the segments that need to be ON for Digit 1.
   • Turn ON the transistor for Digit 1's cathode (set GPIO low).
   • Wait for a short period (e.g., 1-5ms).
   • Turn OFF the Digit 1 cathode.
   • Set the GPIOs for the anode pins for Digit 2.
   • Turn ON the transistor for Digit 2's cathode.
   • Wait for a short period.
   • Repeat. The human eye perceives this rapid switching as both digits being continuously lit.
3. Current Calculation: If each digit is ON for 50% of the time (50% duty cycle) and you want an average segment current of 5mA, you would set the instantaneous current during its ON time to 10mA. The resistor value would be calculated using this 10mA figure.

11. Operating Principle

The device operates on the principle of electroluminescence in a semiconductor P-N junction. When a forward voltage exceeding the junction's built-in potential (approximately 2.0-2.6V for AlInGaP) is applied, electrons from the N-type material recombine with holes from the P-type material in the active region. This recombination event releases energy in the form of photons (light). The specific composition of the AlInGaP crystal lattice determines the bandgap energy, which directly dictates the wavelength (color) of the emitted light\u2014in this case, in the red spectrum (631-639 nm). The seven segments are individual LED chips arranged in a figure-eight pattern. By selectively powering different combinations of these segments, the numerals 0-9 and some letters can be formed.

12. Technology Trends and Context

This product represents a mature and highly optimized segment of LED display technology. AlInGaP is a well-established material system for high-efficiency red, orange, and amber LEDs. Current trends in display technology are moving towards higher-density, full-color solutions like OLEDs and micro-LEDs for complex graphics. However, seven-segment LED displays remain irreplaceable in applications prioritizing extreme reliability, long lifespan (often exceeding 100,000 hours), low cost, high brightness, simplicity of interface, and excellent readability in various lighting conditions. Developments in this field focus on further increasing efficiency (lumens per watt), improving contrast ratios, and enabling even lower driving currents for ultra-low-power IoT devices, ensuring this technology's continued relevance in industrial, instrumentation, and specific consumer applications for the foreseeable future.