LTP-4323JD LED Display Datasheet - 0.4-inch Digit Height - Hyper Red Color - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTP-4323JD is a high-performance, dual-character alphanumeric display module designed for applications requiring clear, bright, and reliable numeric and limited alphabetic readouts. Its core technology is based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material, specifically engineered to emit light in the Hyper Red spectrum. This material choice, grown on a non-transparent Gallium Arsenide (GaAs) substrate, provides superior efficiency and brightness for red emissions compared to older technologies. The device features a gray face with white segments, offering high contrast for excellent readability under various lighting conditions. It is categorized for luminous intensity, ensuring consistent performance across production batches, and is available in a lead-free package compliant with RoHS directives.

1.1 Key Features and Advantages

• Compact and Legible: Features a 0.4-inch (10.0 mm) digit height, making it suitable for space-constrained panels while maintaining excellent character definition.
• Superior Optical Performance: Offers high brightness, high contrast, and a wide viewing angle due to the AlInGaP LED chips and continuous uniform segment design.
• Energy Efficient: Has low power requirements, contributing to lower overall system power consumption.
• Design Flexibility: Available in a common cathode configuration (as per this datasheet), simplifying driver circuit design for many microcontroller-based systems.
• Robust Construction: Provides solid-state reliability with excellent character appearance and is easy to mount on standard printed circuit boards (PCBs).
• Environmental Compliance: Packaged as a lead-free component, adhering to modern environmental standards.

1.2 Target Applications and Market

This display is intended for use in ordinary electronic equipment across various sectors. Typical applications include instrumentation panels, test and measurement equipment, point-of-sale systems, industrial control interfaces, consumer appliances, and communication devices. It is designed for applications where reliable, clear, and bright alphanumeric indication is required. The datasheet explicitly cautions against using this standard commercial-grade component in safety-critical systems (e.g., aviation, medical life-support, transportation control) without prior consultation, highlighting its primary market in general-purpose industrial and consumer electronics.

2. Technical Specifications and Objective Interpretation

The following section provides a detailed, objective analysis of the device's electrical, optical, and thermal characteristics as defined 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 or at these limits is not guaranteed.

• Power Dissipation per Segment: 70 mW. This is the maximum power that can be safely dissipated by a single LED segment without risk of overheating.
• Peak Forward Current per Segment: 90 mA. This current is permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) for brief periods, not for continuous operation.
• Continuous Forward Current per Segment: 25 mA at 25°C. This current derates linearly at 0.33 mA/°C as ambient temperature (Ta) increases above 25°C. For example, at 85°C, the maximum continuous current would be approximately: 25 mA - ((85°C - 25°C) * 0.33 mA/°C) ≈ 5.2 mA.
• Temperature Range: Operating and storage temperature range is -35°C to +85°C.
• Solder Condition: The device can withstand soldering at 260°C for 5 seconds, measured 1/16 inch (≈1.59 mm) below the seating plane.

2.2 Electrical and Optical Characteristics

These are the typical and maximum/minimum performance parameters measured under specified test conditions (Ta=25°C).

• Average Luminous Intensity (Iv): Ranges from 200 μcd (Min) to 650 μcd (Max), with a typical value provided, tested at IF=1mA. This indicates the brightness output.
• Forward Voltage per Segment (VF): Typically 2.6V, with a maximum specified, at IF=20mA. Designers must ensure the driving circuit can provide sufficient voltage to achieve the desired current across all units, considering this VF range.
• Peak Emission Wavelength (λp): 650 nm. This is the wavelength at which the emitted light intensity is highest, defining the \"Hyper Red\" color.
• Dominant Wavelength (λd): 639 nm. This is the single wavelength perceived by the human eye to match the color of the light, crucial for color specification.
• Spectral Line Half-Width (Δλ): 20 nm. This indicates the spectral purity; a smaller value means a more monochromatic light.
• Reverse Current (IR): Maximum 100 μA at VR=5V. The datasheet strongly notes that this reverse voltage condition is for test purposes only and the device cannot operate continuously under reverse bias.
• Luminous Intensity Matching Ratio: 2:1 maximum for segments within the same \"similar light area.\" This specifies the allowable brightness variation between segments in one character.
• Cross Talk: Specified as ≤ 2.5%, referring to unwanted optical interference between adjacent segments.

3. Binning and Categorization System

The LTP-4323JD employs a categorization system for luminous intensity. This means units are tested and sorted into different performance bins based on their measured light output. The module marking includes a \"Z: BIN CODE\" identifier. This allows designers to select displays with consistent brightness levels for a uniform appearance in multi-unit applications. The datasheet does not detail the specific bin code values or intensity ranges associated with each code, which would typically be defined in a separate binning document or agreed upon during purchase.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical/Optical Characteristics Curves.\" While 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, critical for designing constant-current drivers.
• Luminous Intensity vs. Forward Current (I-L Curve): 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 derating of light output as temperature increases, which is vital for applications in non-climate-controlled environments.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at 650nm and the 20nm half-width.

These curves are essential for understanding the device's behavior under non-standard conditions (different currents, temperatures) and for optimizing the design for efficiency and longevity.

5. Mechanical and Package Information

5.1 Package Dimensions

The display has a standard dual in-line package (DIP) footprint. Key dimensional notes include:

• All dimensions are in millimeters with a general tolerance of ±0.25 mm unless otherwise specified.
• Pin tip shift tolerance is 0.4 mm.
• Specific quality limits are set for foreign material on segments (≤10 mils), ink contamination (≤20 mils), bending of the reflector (≤1/100 of its length), and bubbles in the segment (≤10 mils).
• The recommended PCB hole diameter for the leads is Ø1.30mm.

5.2 Pinout and Polarity Identification

The device has 20 pins. The internal circuit diagram and pin connection table show it is a common cathode type for this specific part number (LTP-4323JD). Each segment (A, B, C, D, E, F, G, H, K, M, N, P, R, S, T, U, DP) has its own anode pin. The two characters share common cathode pins (Pin 4 for Character 1, Pin 10 for Character 2). Pin 14 is listed as \"No Connection.\" Correct identification of the common cathode pins is crucial for proper circuit design to sink current correctly.

6. Soldering and Assembly Guidelines

6.1 Automated Soldering Profile

For wave or reflow soldering, the condition is specified as 260°C for 5 seconds, measured 1.59mm (1/16 inch) below the seating plane of the component. The temperature of the component body itself during assembly must not exceed the maximum temperature rating.

6.2 Manual Soldering Instructions

For hand soldering, the iron tip should be applied 1.59mm below the seating plane. The soldering time must be within 5 seconds at a temperature of 350°C ±30°C. Exceeding these time or temperature limits can damage the internal wire bonds or the LED chips.

7. Reliability Testing

The device undergoes a comprehensive suite of reliability tests based on military (MIL-STD), Japanese industrial (JIS), and internal standards. These tests validate its robustness and longevity:

• Operating Life Test (RTOL): 1000 hours of continuous operation at maximum rated current to test for long-term luminous degradation and failure.
• Environmental Stress Tests: Includes High Temperature/Humidity Storage (500 hrs at 65°C/90-95% RH), High Temperature Storage (1000 hrs at 105°C), and Low Temperature Storage (1000 hrs at -35°C).
• Thermal Cycling & Shock: Temperature Cycling (30 cycles between -35°C and 105°C) and Thermal Shock (30 cycles between -35°C and 105°C with rapid transitions) to test for mechanical failures due to coefficient of thermal expansion (CTE) mismatches.
• Solderability Tests: Solder Resistance (10 sec at 260°C) and Solderability (5 sec at 245°C) ensure the leads can withstand assembly processes.

8. Critical Application Notes and Design Considerations

8.1 Design and Implementation Warnings

• Drive Current and Thermal Management: Exceeding the recommended continuous forward current or operating temperature will accelerate light output degradation (lumen depreciation) and can lead to premature catastrophic failure. The linear derating curve for current must be respected.
• Circuit Protection: The driving circuit must incorporate protection against reverse voltages and voltage transients during power-up or shutdown sequences, as LEDs have low reverse breakdown voltages.
• Constant Current Drive: This is the recommended method for driving LEDs. It ensures consistent brightness across units and over temperature variations, as it compensates for the negative temperature coefficient of the LED's forward voltage.
• Forward Voltage Consideration: The power supply or driver circuit must be designed to accommodate the full range of forward voltage (VF, typ. 2.6V, max as per spec) to guarantee the target drive current is delivered to all segments under all conditions.

8.2 Typical Application Circuit Concepts

For a common cathode display like the LTP-4323JD, a typical multiplexing scheme is often used to control the 16 segments across two characters. The common cathode pins (4 and 10) would be switched to ground sequentially (e.g., by a transistor), while the appropriate segment anode pins are driven high (with current limiting resistors or a constant current driver IC) to illuminate the desired segments for that character. This reduces the required number of microcontroller I/O pins. The design must ensure the peak current per segment during the multiplexed pulse does not exceed the absolute maximum rating, and the average current over time meets the desired brightness level.

9. Comparative Advantages and Technology Context

The use of AlInGaP technology for red LEDs represents a significant advancement over older technologies like Gallium Arsenide Phosphide (GaAsP). AlInGaP offers substantially higher external quantum efficiency, resulting in brighter output for the same input current. The \"Hyper Red\" emission (650nm peak) is also more visually distinct and can offer better performance in applications where the display might be viewed through filters or in ambient sunlight. The gray face/white segment design maximizes contrast. Compared to simple 7-segment displays, the 16-segment format allows for a more complete representation of the alphabet (albeit limited), increasing the device's utility in applications requiring short text messages alongside numbers.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display with a 5V microcontroller pin directly?
A: No. The typical forward voltage is 2.6V, but a series current-limiting resistor is always required to set the correct current (e.g., 20mA). Using just a 5V pin would cause excessive current and destroy the LED segment. Calculate the resistor value using R = (Vcc - Vf) / If.

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (650nm) is the physical peak of the light spectrum emitted. Dominant wavelength (639nm) is the perceived color point by the human eye, which can differ due to the shape of the emission spectrum. Both are important for specification.

Q: Why is constant current drive recommended over constant voltage?
A: An LED's forward voltage (Vf) decreases as temperature increases. With a constant voltage supply, this would cause the current to increase, leading to further heating and thermal runaway. A constant current source maintains a stable current regardless of Vf variations, ensuring stable brightness and protecting the LED.

Q: How do I interpret the \"Luminous Intensity Matching Ratio\" of 2:1?
A: This means the brightest segment in a defined \"similar light area\" (likely within one character) will be no more than twice as bright as the dimmest segment in that same area. It is a measure of uniformity.

11. Practical Design and Usage Example

Scenario: Designing a simple two-digit voltmeter readout. The LTP-4323JD would be ideal. The microcontroller's ADC reads a voltage, converts it to a decimal number, and drives the display. The firmware would handle multiplexing: it sets the segment pattern for the tens digit on the anode lines, grounds common cathode Pin 4 for a short period (e.g., 5ms), then sets the segment pattern for the units digit and grounds common cathode Pin 10 for the same period, repeating rapidly. The persistence of vision creates the illusion of both digits being on continuously. Careful calculation of the current-limiting resistors is needed based on the supply voltage and the desired average segment current (considering the duty cycle of multiplexing). The design must include protection diodes if the driving circuit can subject the LEDs to reverse voltage.

12. Operating Principle

The device operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's turn-on threshold is applied, electrons from the n-type AlInGaP layer recombine with holes from the p-type layer. This recombination event releases energy in the form of photons (light). The specific alloy composition of the AlInGaP crystal lattice determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, in the red region around 650 nm. The non-transparent GaAs substrate absorbs any downward-emitted light, improving overall efficiency by reflecting it upwards. Each segment in the display contains one or more of these microscopic LED chips.

13. Technology Trends and Context

AlInGaP-based LEDs represent a mature and highly optimized technology for amber, red, and hyper-red emissions. While newer materials like Gallium Nitride (GaN) dominate the blue, green, and white LED markets, AlInGaP remains the efficiency leader for longer wavelengths. Current trends in display technology focus on miniaturization (smaller than 0.4-inch digits), higher pixel density (moving towards dot matrix or OLED for full graphics), and improved efficiency (lower drive currents for the same brightness). However, for dedicated, high-reliability, high-brightness alphanumeric indicators in harsh environments (wide temperature range), segment LED displays like the LTP-4323JD continue to be a robust and cost-effective solution. Future developments may involve integrating driver electronics directly into the package or further refining the package for even better thermal management.