LTD-5023AJD LED Display Datasheet - 0.56-inch Digit Height - 2.6V Forward Voltage - Hyper Red Color - English Technical Document

1. Product Overview

The LTD-5023AJD is a two-digit, seven-segment plus decimal point LED display module. It features a digit height of 0.56 inches (14.22 mm), providing clear and legible numeric output suitable for various instrumentation and display applications. The device utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) Hyper Red LED chips, which are epitaxially grown on a GaAs substrate. This technology is known for its high efficiency and excellent luminous performance. The display presents a light gray face with white segments, offering a classic and high-contrast appearance that enhances readability under various lighting conditions.

1.1 Core Advantages

• High Brightness & Contrast: The AlInGaP technology delivers superior luminous intensity, ensuring the display is easily visible.
• Wide Viewing Angle: Provides consistent brightness and color across a broad range of viewing positions.
• Low Power Requirement: Designed for efficient operation, making it suitable for battery-powered or energy-conscious devices.
• Excellent Character Appearance: Features continuous, uniform segments for a clean and professional numeric display.
• Solid-State Reliability: LEDs offer long operational life and robustness against shock and vibration compared to other display technologies.
• Categorized for Luminous Intensity: Devices are binned for consistent brightness levels, aiding in design uniformity.
• Lead-Free Package: Compliant with environmental regulations (e.g., RoHS).

1.2 Target Market

This display is ideal for applications requiring reliable, bright, and easy-to-read numeric indicators. Common use cases include test and measurement equipment, industrial control panels, medical devices, consumer appliances, automotive dashboards (secondary displays), and point-of-sale terminals.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed.

• Power Dissipation per Segment: 70 mW maximum.
• Peak Forward Current per Segment: 90 mA (at 1 kHz, 10% duty cycle). This rating is for pulsed operation to achieve higher instantaneous brightness without overheating.
• Continuous Forward Current per Segment: 25 mA at 25°C. This current derates linearly at a rate of 0.33 mA/°C as ambient temperature increases above 25°C. For example, at 85°C, the maximum allowable continuous current would be approximately: 25 mA - ((85°C - 25°C) * 0.33 mA/°C) = 5.2 mA.
• Reverse Voltage per Segment: 5 V maximum. Exceeding this can break down the LED junction.
• Operating & Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: Withstands a maximum of 260°C for up to 3 seconds, measured 1.6mm below the seating plane, which is critical for reflow soldering processes.

2.2 Electrical & Optical Characteristics (Ta=25°C)

These are the typical performance parameters under specified test conditions.

• Average Luminous Intensity (I_V): Ranges from 320 μcd (min) to 700 μcd (max) at a forward current (I_F) of 1 mA. At 10 mA, the typical intensity is 16250 μcd (16.25 mcd). This high efficiency is a hallmark of AlInGaP technology.
• Peak Emission Wavelength (λ_p): 650 nm (typical). This defines the spectral peak of the light output, placing it in the hyper-red region of the spectrum.
• Spectral Line Half-Width (Δλ): 20 nm (typical). This indicates the spectral purity; a narrower width means a more monochromatic color.
• Dominant Wavelength (λ_d): 639 nm (typical). This is the wavelength perceived by the human eye and is crucial for color specification.
• Forward Voltage per Segment (V_F): 2.1 V (min), 2.6 V (typical) at I_F=20 mA. This parameter is essential for designing the current-limiting circuitry.
• Reverse Current per Segment (I_R): 100 μA (max) at a reverse voltage (V_R) of 5V.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (max) at I_F=1 mA. This specifies the maximum allowable brightness variation between segments within a device, ensuring visual uniformity.

Note: Luminous intensity measurements use a sensor and filter approximating the CIE photopic eye-response curve for accuracy relevant to human vision.

3. Binning System Explanation

The datasheet indicates the device is \"Categorized for Luminous Intensity.\" This implies a binning process where displays are sorted based on measured optical output at a standard test current (likely 1 mA or 10 mA). Designers can select bins to ensure consistent brightness across multiple units in a product, avoiding noticeable variations between displays. While specific bin codes are not provided in this excerpt, typical bins are defined by ranges of luminous intensity (e.g., Bin A: 500-600 μcd, Bin B: 600-700 μcd).

4. Performance Curve Analysis

The datasheet references \"Typical Electrical / Optical Characteristic Curves.\" Although not displayed in the provided text, such curves typically include:

• I-V (Current-Voltage) Curve: Shows the relationship between forward voltage and current for a segment. It is non-linear, with a turn-on voltage around 1.8-2.0V for AlInGaP, rising to the typical 2.6V at 20 mA.
• Luminous Intensity vs. Forward Current: A graph showing how light output increases with current. It is generally linear at lower currents but may saturate at higher currents due to thermal effects.
• Luminous Intensity vs. Ambient Temperature: Demonstrates how light output decreases as temperature increases. AlInGaP LEDs have good high-temperature performance compared to some other materials, but derating is still necessary.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at ~650 nm and the 20 nm half-width.

These curves are vital for understanding device behavior under non-standard conditions and for optimizing drive conditions for specific application needs (e.g., maximizing brightness vs. maximizing efficiency or lifespan).

5. Mechanical & Package Information

5.1 Package Dimensions

The device comes in a standard dual in-line package (DIP). All dimensions are specified in millimeters with a general tolerance of ±0.25 mm (0.01\"). The exact outline, segment spacing, lead spacing, and overall height/width/length are defined in the dimension drawing on page 2 of the datasheet. This drawing is critical for PCB footprint design and mechanical integration into the end product.

5.2 Pin Connection & Internal Circuit

The LTD-5023AJD is a common cathode type display. This means the cathodes (negative terminals) of the LEDs for each digit are connected together internally. The pinout is as follows:

• Pins 1-4, 15-18: Control the segments (A, B, C, D, E, F, G, DP) of Digit 1.
• Pins 5-13: Control the segments (A, B, C, D, E, F, G, DP) and the common cathode of Digit 2.
• Pin 14: Common cathode for Digit 1.

The internal circuit diagram shows the arrangement of the 14 LED segments (7 per digit, plus two decimal points) and their connection to the 18 pins. Multiplexing is required to drive both digits: by alternately enabling the cathode of Digit 1 and Digit 2 while supplying anode signals for the desired segments of the active digit, both digits can be controlled with fewer I/O lines.

6. Soldering & Assembly Guidelines

The absolute maximum rating specifies a soldering temperature profile: the package can withstand a peak temperature of 260°C for a maximum of 3 seconds, measured at a point 1.6mm (1/16 inch) below the seating plane (i.e., on the PCB near the lead). This is a standard rating for lead-free reflow soldering processes (e.g., using SAC305 solder). Designers must ensure their reflow oven profile stays within these limits to prevent damage to the LED chips or the plastic package. Standard ESD (Electrostatic Discharge) precautions should be observed during handling. Storage should be within the specified -35°C to +85°C range in a low-humidity environment.

7. Application Suggestions

7.1 Typical Application Circuits

To drive this display, a microcontroller or dedicated driver IC is needed. For common cathode displays, the cathode pins are connected to ground (via a transistor switch for multiplexing), and the anode pins are connected to a current-limited voltage source (e.g., through a series resistor or constant current driver). The forward voltage (V_F) of 2.6V and desired current (I_F, e.g., 10-20 mA for full brightness) determine the series resistor value: R = (V_supply - V_F) / I_F. If multiplexing two digits at 10 mA each, the peak current during the digit's on-time might be 10 mA, but the average current per segment is lower, reducing power consumption.

7.2 Design Considerations

• Current Limiting: Always use series resistors or constant-current drivers. Never connect an LED directly to a voltage source.
• Multiplexing: Essential for multi-digit displays to minimize pin count. Refresh rate should be high enough (>60 Hz) to avoid visible flicker.
• Heat Management: While LEDs are efficient, power dissipation (P = V_F * I_F) per segment can reach up to 52 mW (2.6V * 20mA). Ensure adequate ventilation, especially if driving at high currents or in high ambient temperatures.
• Viewing Angle: The wide viewing angle is beneficial but consider the primary user's sightline when mounting the display.

8. Technical Comparison

Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) red LEDs, the AlInGaP Hyper Red LED offers significantly higher luminous efficiency (more light output per mA of current) and better performance at elevated temperatures. Compared to white LEDs (often blue LED + phosphor), it offers superior color purity and typically higher efficiency for monochromatic red light. The 0.56\" digit height is a common size, offering a good balance between readability and compactness compared to smaller (0.3\") or larger (0.8\") displays.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the difference between peak wavelength (650nm) and dominant wavelength (639nm)?
A: Peak wavelength is the highest point on the spectral output curve. Dominant wavelength is the single wavelength of monochromatic light that would appear to have the same color to the human eye. They often differ slightly.

Q: Can I drive this display with a 3.3V microcontroller?
A: Yes. With a V_F of 2.6V, a 3.3V supply is sufficient. A series resistor would be: R = (3.3V - 2.6V) / 0.020A = 35 Ohms. A standard 33 or 39 Ohm resistor would be suitable.

Q: Why is the peak forward current (90mA) much higher than the continuous current (25mA)?
A> The LED can handle short, high-current pulses without overheating, allowing for brighter display multiplexing schemes (where each digit is only on for a fraction of the time) or for creating very bright flashes.

Q: What does \"AlInGaP epi on GaAs substrate\" mean?
A> The light-emitting layers (the epitaxial or \"epi\" layers) are made of Aluminum Indium Gallium Phosphide. These are grown on a Gallium Arsenide (GaAs) wafer which provides structural support but is not the primary light-emitting material.

10. Practical Use Case Example

Scenario: Designing a simple digital voltmeter display.
The voltmeter circuit produces a BCD (Binary-Coded Decimal) output corresponding to a voltage reading. A microcontroller reads this BCD value. It then uses a look-up table to determine which segments (A-G) to illuminate for each digit to display the number. The microcontroller's I/O pins, connected through current-limiting resistors, drive the anode pins of the LTD-5023AJD. Two other I/O pins, connected to transistor switches, control the common cathode pins (14 and 13). The software rapidly alternates (multiplexes) between enabling Digit 1 and Digit 2, while sending the correct anode patterns for each digit. The 0.56\" size provides clear reading from a typical bench distance, and the high contrast ensures visibility under workshop lighting. The low power consumption is beneficial if the meter is portable.

11. Technology Principle Introduction

AlInGaP is a III-V semiconductor compound. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region where they recombine. This recombination process releases energy in the form of photons (light). The specific composition of Aluminum, Indium, Gallium, and Phosphide in the crystal lattice determines the bandgap energy, which directly dictates the wavelength (color) of the emitted light. For the Hyper Red color, the bandgap is tuned to emit photons around 650 nm. The GaAs substrate is optically absorbent at this wavelength, so the light is typically extracted from the top surface of the chip. The \"Hyper Red\" designation indicates a deep, saturated red color with high luminous efficacy.

12. Technology Development Trends

LED display technology continues to evolve. While AlInGaP remains the dominant material for high-efficiency red and amber LEDs, trends include:

• Increased Efficiency: Ongoing material science and chip design improvements yield more lumens per watt, enabling brighter displays at lower power.
• Miniaturization: Development of smaller chip geometries allows for higher resolution displays or smaller package sizes.
• Improved Thermal Management: New package materials and designs better dissipate heat, allowing for higher drive currents and sustained brightness.
• Integration: Move towards displays with integrated driver ICs (\"intelligent displays\") to simplify system design.
• Color Gamut Expansion: While this is a monochromatic device, broader trends involve developing new phosphors and direct-emission materials for wider color ranges in full-color displays, though AlInGaP red is a key component in such RGB systems.