LTD-5621AJG LED Display Datasheet - 0.56-inch Digit Height - Green Segments - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTD-5621AJG is a dual-digit, seven-segment alphanumeric display module. Its primary function is to provide clear, bright numeric and limited alphanumeric readouts in various electronic devices. The core technology is based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material, which is known for producing high-efficiency light emission in the red, orange, amber, and green spectral regions. This specific device utilizes AlInGaP chips to create green segments.

The display features a gray face, which enhances contrast and improves readability by reducing ambient light reflection. It employs a common anode configuration, meaning the anodes of the LEDs for each digit are connected together internally, simplifying the driving circuitry in multiplexed applications. The device is categorized for luminous intensity, ensuring consistent brightness levels across production batches.

2. Technical Specifications Deep Dive

2.1 Optical Characteristics

The optical performance is central to the display's functionality. The average luminous intensity (Iv) is specified with a minimum of 320 µcd, a typical value of 900 µcd, and no stated maximum, when driven at a forward current (IF) of 1mA. This high brightness, combined with the gray face, results in excellent contrast. The dominant wavelength (λd) is 572 nm, placing the emission solidly in the green portion of the visible spectrum. The spectral line half-width (Δλ) is 15 nm, indicating a relatively pure color output. Luminous intensity matching between segments is guaranteed to be within a 2:1 ratio, ensuring uniform appearance across the display.

2.2 Electrical Characteristics

The forward voltage (VF) per segment is typically 2.6V with a maximum of 2.6V at a test current of 20mA. The low power requirement is a key feature, with a continuous forward current per segment rated at 25 mA. A derating factor of 0.33 mA/°C applies above 25°C. The absolute maximum reverse voltage per segment is 5V. The reverse current (IR) is a maximum of 100 µA at 5V reverse bias.

2.3 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage may occur. The maximum power dissipation per segment is 70 mW. A peak forward current of 60 mA is allowed under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). The device is rated for an operating and storage temperature range of -35°C to +85°C. The solder temperature must not exceed 260°C for more than 3 seconds, measured 1.6mm below the seating plane of the package.

3. Binning System Explanation

The datasheet indicates that the device is "categorized for luminous intensity." This implies a binning or sorting process based on measured light output. While specific bin codes are not provided in this document, typical categorization ensures that displays within a certain order have similar brightness levels, preventing noticeable differences in multi-digit or multi-unit installations. Designers should consult the manufacturer for the specific binning structure and available ranges when consistency is critical.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristic Curves." Although the specific graphs are not detailed in the provided text, such curves typically include:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the nonlinear relationship, crucial for designing current-limiting circuits.
• Luminous Intensity vs. Forward Current: Demonstrates how light output increases with current, often becoming sub-linear at higher currents due to heating effects.
• Luminous Intensity vs. Ambient Temperature: Shows the decrease in light output as junction temperature rises, important for high-temperature or high-drive applications.
• Spectral Distribution: A plot of relative intensity versus wavelength, confirming the dominant wavelength and spectral width.

These curves are essential for optimizing drive conditions for a balance of brightness, efficiency, and longevity.

5. Mechanical and Package Information

The display has a digit height of 0.56 inches (14.22 mm). The package dimensions are provided in a drawing with all measurements in millimeters. Tolerances are ±0.25 mm unless otherwise specified. The internal circuit diagram shows the common anode connection for each digit and the individual cathodes for each segment (A-G and Decimal Point). The pin connection table lists 18 pins, detailing the cathode connections for segments and decimal points for both digits, as well as the common anode pins for digit 1 and digit 2. This precise mapping is critical for correct PCB layout and software driving routines.

6. Soldering and Assembly Guidelines

The key assembly specification is the soldering temperature limit: a maximum of 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This is a standard reflow soldering profile constraint to prevent damage to the LED chips and internal wire bonds from excessive heat. Standard industry practices for handling moisture-sensitive devices (MSL) may apply, though not explicitly stated. Storage should be within the specified temperature range of -35°C to +85°C in a dry environment.

7. Packaging and Ordering Information

The part number is LTD-5621AJG. The "AJG" suffix likely encodes specific attributes: "A" may relate to the AlInGaP technology, "J" could indicate a right-hand decimal point (as noted in the description), and "G" confirms green segments. The document does not specify tape-and-reel, tube, or tray packaging details. For production, the full specification number DS30-2001-383 and document revision should be referenced.

8. Application Recommendations

8.1 Typical Application Scenarios

This display is suitable for applications requiring clear, medium-sized numeric readouts. Examples include industrial control panels, test and measurement equipment, medical devices, point-of-sale terminals, appliance control panels, and automotive aftermarket gauges. Its wide viewing angle and high contrast make it effective in varied lighting conditions.

8.2 Design Considerations

• Drive Circuitry: Use constant current drivers or appropriate current-limiting resistors for each cathode line. The common anode configuration is ideal for multiplexing. A suitable multiplexing driver IC can control the segments and digit selection.
• Current Setting: Operate at or below the continuous forward current rating (25mA per segment). Higher currents increase brightness but also heat, reducing lifespan. The typical 900µcd at 1mA suggests very good efficiency; often 10-20mA provides ample brightness.
• Power Dissipation: Calculate total power dissipation, especially when multiple segments are lit simultaneously, to ensure it remains within limits, considering ambient temperature.
• PCB Layout: Follow the recommended pad pattern from the dimension drawing. Ensure clean signal paths to avoid flicker in multiplexed operation.

9. Technical Comparison

Compared to older technologies like standard GaP or GaAsP LEDs, AlInGaP offers significantly higher luminous efficiency and better temperature stability, resulting in brighter displays with more consistent color. Compared to single-digit displays, this dual-digit unit saves board space and simplifies assembly. The common anode design is more common and often easier to interface with modern microcontroller GPIO pins configured as current sinks.

10. Frequently Asked Questions (FAQ)

Q: What is the purpose of the gray face?

A: The gray face acts as a low-reflectance background, significantly improving the contrast ratio between the lit green segments and the surrounding area, especially under bright ambient light.

Q: How do I drive this display with a microcontroller?

A: You will need external transistors or a dedicated driver IC. The microcontroller would control the segment cathodes (as outputs set low to turn on) and digit anode commons (via transistor switches) in a fast multiplexing sequence.

Q: Can I use this display in an automotive dashboard?

A: The operating temperature range (-35°C to +85°C) covers most automotive passenger compartment environments. Ensure proper current derating and consider potential voltage transients from the vehicle's electrical system.

Q: What does "categorized for luminous intensity" mean for my design?

A: It means you can expect uniform brightness within a single display and potentially across multiple displays from the same batch. For critical applications, specify the required intensity bin to the supplier.

11. Practical Design Case

Consider designing a simple two-digit counter. The microcontroller would have 8 I/O pins connected to the segment cathodes (A-G, DP) via current-limiting resistors. Two additional I/O pins would control NPN transistors, whose collectors are connected to the common anodes (pins 13 & 14) and emitters to the positive supply (e.g., 5V). The software routine would:

1. Turn off both digit transistors.

2. Set the segment pattern for Digit 1 on the cathode lines.

3. Enable the transistor for Digit 1's anode for a short period (e.g., 5ms).

4. Turn off Digit 1's transistor.

5. Set the segment pattern for Digit 2.

6. Enable Digit 2's transistor for 5ms.

7. Repeat at a rate faster than 60Hz to avoid visible flicker. The resistor value is calculated based on the supply voltage (5V), LED forward voltage (~2.6V), and desired segment current (e.g., 15mA): R = (5V - 2.6V) / 0.015A ≈ 160 ohms.

12. Technology Principle Introduction

AlInGaP (Aluminium Indium Gallium Phosphide) is a III-V compound semiconductor. By precisely adjusting the ratios of its constituent elements, the bandgap energy of the material can be engineered. When electrons and holes recombine across this bandgap, photons are emitted. For the LTD-5621AJG, the composition is tuned to produce photons with an energy corresponding to green light (~572 nm). The chips are grown on a non-transparent GaAs substrate. The gray face material is typically an epoxy or silicone-based encapsulant with diffusing pigments added to create the desired background color and viewing angle properties.

13. Technology Trends

While AlInGaP remains a high-performance technology for red, amber, and green LEDs, the broader display industry trend is towards higher pixel densities and full-color capability. Seven-segment displays occupy a stable niche in applications where simple, low-cost, high-brightness, and highly readable numeric output is required. Trends within this niche include the development of even higher efficiency materials, thinner packages, and displays with integrated drivers and controllers ("intelligent displays") to further simplify system design. The move towards wider operating temperature ranges and enhanced reliability for automotive and industrial applications is also ongoing.