LTD-5623AJG LED Display Datasheet - 0.56-inch Digit Height - AlInGaP Green - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Documentation

1. Product Overview

The LTD-5623AJG is a dual-digit, seven-segment light-emitting diode (LED) display module. Its primary function is to provide a clear, bright numeric readout for various electronic devices and instrumentation. The core application is in scenarios requiring the display of two decimal digits, such as counters, timers, measurement equipment, and industrial control panels.

The device's key positioning lies in its balance of performance and reliability. It utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for the LED chips, which is known for producing high-efficiency light emission in the green and yellow spectral regions. The display features a gray faceplate with green illuminated segments, offering high contrast for excellent readability.

1.1 Core Advantages and Target Market

The display offers several distinct advantages that make it suitable for professional and industrial applications:

• High Brightness & Contrast: The AlInGaP technology and gray face combination deliver luminous intensity typically up to 900 µcd, ensuring visibility even in well-lit environments.
• Low Power Requirement: It operates efficiently, making it suitable for battery-powered or energy-conscious devices.
• Wide Viewing Angle: The design allows the displayed numbers to be read from a broad range of angles.
• Solid-State Reliability: As an LED-based device, it offers long operational life, shock resistance, and fast switching times compared to other display technologies.
• Categorized Luminous Intensity: Devices are binned for intensity, allowing for consistent brightness matching in multi-digit applications.
• Lead-Free Package: The component is compliant with RoHS (Restriction of Hazardous Substances) directives.

The target market includes manufacturers of test and measurement equipment, process control systems, medical devices, consumer appliances with numeric displays, and any embedded system requiring a robust and reliable two-digit numeric output.

2. In-Depth Technical Parameter Analysis

This section provides a detailed, objective interpretation of the key electrical and optical parameters specified in the datasheet.

2.1 Absolute Maximum Ratings

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

• Power Dissipation per Segment: 70 mW. This is the maximum power that can be safely dissipated by a single LED segment (e.g., segment 'A') without causing overheating.
• Peak Forward Current per Segment: 60 mA. This is the maximum allowable pulsed current, typically specified at a 1/10 duty cycle and 0.1ms pulse width. It is used for multiplexing or brief overdrive for extra brightness.
• Continuous Forward Current per Segment: 25 mA at 25°C. This current derates linearly to 0 mA at 105°C (at a rate of 0.28 mA/°C). This is the maximum DC current for continuous operation under normal temperature conditions.
• Reverse Voltage per Segment: 5 V. Applying a reverse voltage higher than this can break down the LED junction.
• Operating & Storage Temperature Range: -35°C to +105°C. The device is rated for industrial temperature ranges.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at Ta=25°C under specified test conditions.

• Average Luminous Intensity (I_V): Ranges from 320 µcd (Min) to 900 µcd (Typ) at a forward current (I_F) of 1 mA. This parameter is binned.
• Peak Emission Wavelength (λ_p): 571 nm (Typ). This is the wavelength at which the optical power output is maximum, defining the green color.
• Forward Voltage per Segment (V_F): 2.05V (Min), 2.6V (Typ) at I_F=20 mA. This is the voltage drop across the LED when operating. Designers must ensure the driving circuit can provide this voltage.
• Reverse Current per Segment (I_R): 100 µA (Max) at V_R=5V. This is the small leakage current when the LED is reverse-biased.
• Luminous Intensity Matching Ratio: 2:1 (Max). This specifies the maximum allowable ratio between the brightest and dimmest segments within the "similar light area," ensuring uniform appearance.

3. Binning System Explanation

The datasheet indicates that the luminous intensity is categorized. While specific bin codes are not provided in this excerpt, the principle is critical for design.

• Luminous Intensity Binning: LEDs are sorted (binned) based on their measured light output at a standard test current (1mA). Using LEDs from the same or adjacent bins in a multi-digit or multi-segment display ensures uniform brightness across the entire readout, preventing some digits from appearing brighter than others. Designers should specify the required intensity bin when ordering for consistency in production.

4. Performance Curve Analysis

The datasheet references typical characteristic curves. While the graphs are not reproduced here, their implications are analyzed.

• I-V (Current-Voltage) Curve: This curve would show the relationship between forward current (I_F) and forward voltage (V_F). It is non-linear, with a threshold voltage (around 1.8-2.0V for AlInGaP) below which very little current flows. The curve helps in designing current-limiting circuitry.
• Luminous Intensity vs. Forward Current: This graph would show that light output increases with current but may become sub-linear at very high currents due to heating and efficiency droop. The typical operating point of 20mA is chosen for a good balance of brightness and efficiency.
• Temperature Dependence: Characteristic curves are noted to be at 25°C unless specified. In practice, V_F has a negative temperature coefficient (it decreases as temperature rises), while luminous intensity typically decreases with increasing junction temperature. The derating of continuous current is a direct result of thermal management needs.

5. Mechanical & Package Information

5.1 Dimensions and Tolerances

The package is a through-hole type with 18 pins. Key dimensional notes include:

• Digit Height: 0.56 inches (14.22 mm).
• General Tolerances: ±0.25 mm unless otherwise noted.
• Pin Tip Shift Tolerance: ±0.4 mm, important for PCB hole alignment.
• Recommended PCB Hole: Ø1.0 mm.
• Quality Tolerances: Specifications for foreign material (≤10 mils), ink contamination (≤20 mils), bending (≤1/100), and bubbles in segments (≤10 mils) are defined to ensure visual quality.

5.2 Pin Connection and Polarity

The device has a common cathode configuration. Each digit (Digit 1 and Digit 2) has its own common cathode pin (Pin 14 and Pin 13, respectively). The anodes for each segment (A-G and DP) are individually accessible on separate pins for each digit. This configuration is ideal for multiplexed driving, where the cathodes are switched to ground sequentially while the appropriate anode patterns are applied.

6. Soldering and Assembly Guidelines

The datasheet provides specific soldering conditions:

• Hand Soldering: The iron tip should be placed 1/16 inch (approximately 1.6 mm) below the seating plane (the point where the display body meets the leads).
• Temperature & Time: Soldering should be completed within 3 seconds at a maximum temperature of 260°C.
• General Rule: The temperature of the unit during assembly must not exceed the maximum temperature rating (105°C for operation, but the glass transition temperature of the epoxy is the real limit during soldering).
• Storage: Store within the specified temperature range of -35°C to +105°C in a dry environment to prevent moisture absorption.

7. Application Recommendations

7.1 Typical Application Circuits

The most common driving method is multiplexing. Since the display has separate common cathodes for each digit, a microcontroller can rapidly alternate between turning on Digit 1 and Digit 2. When Digit 1's cathode is grounded, the microcontroller outputs the segment pattern for the first digit on the anode pins. It then switches to Digit 2's cathode and outputs the second digit's pattern. This happens faster than the human eye can perceive, creating the illusion of both digits being lit simultaneously. This method drastically reduces the number of required microcontroller I/O pins and power consumption.

7.2 Design Considerations

• Current Limiting Resistors: A series resistor must be used on each anode line (or a common resistor on the cathode if multiplexing with constant current) to limit the forward current to a safe value (e.g., 20 mA). The resistor value is calculated as R = (V_supply - V_F) / I_F.
• Multiplexing Frequency: A refresh rate of at least 60 Hz per digit (120 Hz total scan rate) is recommended to avoid visible flicker.
• Peak Current in Multiplexing: When multiplexed with a 1/2 duty cycle (for two digits), the instantaneous current per segment can be doubled to achieve the same average brightness as DC operation. For example, to get an average of 10 mA, you could pulse at 20 mA with a 50% duty cycle. This must stay within the peak current rating.
• Viewing Angle: Position the display considering its wide viewing angle to maximize readability for the end-user.

8. Technical Comparison and Differentiation

Compared to other seven-segment display technologies:

• vs. Red GaAsP/GaP LEDs: AlInGaP green LEDs generally offer higher luminous efficiency and better visibility in a wider range of ambient lighting conditions. The green color is often perceived as brighter by the human eye.
• vs. LCDs: LEDs are emissive (produce their own light), making them clearly visible in darkness without a backlight. They have a much wider operating temperature range, faster response time, and are more robust against physical shock.
• vs. Larger or Smaller Displays: The 0.56-inch digit height is a common size, offering a good balance between being easily readable from a moderate distance and conserving panel space.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display directly from a 5V microcontroller pin?
A: No. The typical forward voltage is 2.6V, and a microcontroller pin cannot source 20mA at 2.6V while also being at a 5V logic high. You must use a transistor or driver IC on the cathode side and/or the anode side. A current-limiting resistor is always mandatory.

Q: What does a "Luminous Intensity Matching Ratio of 2:1" mean in practice?
A: It means that within a single display unit, no segment should be more than twice as bright as any other segment under identical driving conditions. This ensures numerical characters look even and professional.

Q: The peak current is 60mA. Can I run it continuously at 40mA for extra brightness?
A: Absolutely not. The continuous forward current rating is 25 mA at 25°C. Exceeding this will cause excessive heating, rapidly degrade the LED, and likely lead to premature failure. The peak rating is for very short pulses only.

Q: How do I choose the right current-limiting resistor value?
A: Use the formula R = (V_supply - V_F) / I_F. For a 5V supply, a V_F of 2.6V, and a desired I_F of 20mA: R = (5 - 2.6) / 0.02 = 120 Ohms. Use the next standard value (e.g., 120Ω or 150Ω). Always calculate power dissipation in the resistor: P = I² * R.

10. Practical Design and Usage Case

Case: Designing a Simple Two-Digit Counter.
A designer is creating a benchtop frequency counter that needs to display values from 00 to 99. They select the LTD-5623AJG for its clarity and ease of use. The system uses a microcontroller with 18 available I/O pins. The designer connects the 16 anode pins (8 segments/digit x 2 digits) to one port of the microcontroller via 150Ω current-limiting resistors. The two common cathode pins are connected to two NPN transistors (e.g., 2N3904), whose bases are driven by two other microcontroller pins. The software implements a multiplexing routine in a timer interrupt. It turns off both transistors, sets the anode port to the pattern for Digit 1, turns on the transistor for Digit 1's cathode, waits 5ms, then repeats the process for Digit 2. This creates a stable, flicker-free display. The gray face ensures the unlit segments are not distracting, while the bright green lit segments provide excellent contrast against it.

11. Operating Principle Introduction

A seven-segment LED display is an assembly of multiple light-emitting diodes arranged in a figure-eight pattern. Each segment (labeled A through G) and the decimal point (DP) is a separate LED. By selectively illuminating specific combinations of these segments, all decimal digits (0-9) and some letters can be formed. In a common cathode display like the LTD-5623AJG, all the cathodes (negative terminals) of the LEDs for a particular digit are connected together to a single pin. To light a segment, a positive voltage (through a current-limiting resistor) must be applied to its anode pin, while the corresponding digit's common cathode pin is connected to ground (0V). This allows independent control of each segment within a digit and efficient multiplexing across digits.

12. Technology Trends and Context

While surface-mount device (SMD) LEDs and integrated display modules are increasingly common, through-hole seven-segment displays like the LTD-5623AJG remain relevant in specific niches. Their key advantages are ease of prototyping, robustness in high-vibration environments, and excellent visibility from a distance due to their larger size. The use of AlInGaP material represents an advancement over older GaAsP/GaP technology, offering superior efficiency and color purity for green and yellow hues. The trend towards higher efficiency and lower power consumption continues, but the fundamental multiplexing driving principle and application logic for such discrete displays remain stable and widely understood in electronic design.