LTP-3362JD LED Display Datasheet - 0.3-inch Digit Height - AlInGaP Hyper Red - 2.6V Forward Voltage - English Technical Document

1. Product Overview

This document details the specifications for a 0.3-inch (7.62 mm) digit height, dual-digit, 17-segment alphanumeric light-emitting diode (LED) display. The device is engineered to provide clear, legible character representation for applications requiring numeric and limited alphabetic information display. Its core construction utilizes advanced AS-AlInGaP (Aluminum Indium Gallium Phosphide) Hyper Red LED chips, which are grown on a Gallium Arsenide (GaAs) substrate. This technology choice is pivotal for achieving the specific color and performance characteristics outlined in this datasheet. The visual design features a black face with white segments, a combination optimized for high contrast and excellent character appearance under various lighting conditions.

1.1 Core Advantages and Target Applications

The display offers several key benefits that make it suitable for a range of electronic products. Its low power requirement is a significant advantage for battery-operated or energy-conscious devices. The high brightness and high contrast ratio ensure readability in both dim and brightly lit environments. A wide viewing angle allows the displayed information to be seen clearly from various positions, which is crucial for consumer electronics, instrumentation, and public information displays. The solid-state reliability inherent to LED technology ensures long operational life and resistance to shock and vibration compared to other display technologies like vacuum fluorescent or incandescent types. This display is categorized for luminous intensity, meaning units are binned or sorted based on their light output, allowing for consistency in production runs. Typical applications include digital panel meters, test equipment, medical devices, point-of-sale terminals, industrial control panels, and automotive dashboard displays where clear, reliable alphanumeric output is required.

2. Technical Specifications and Objective Interpretation

This section provides a detailed, objective analysis of the electrical, optical, and physical parameters that define the display's performance and limits.

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 and should be avoided in circuit design.

• Power Dissipation per Segment: 70 mW. This is the maximum power a single LED segment can dissipate as heat without risk of damage.
• Peak Forward Current per Segment: 90 mA. This current is permissible only under specific pulsed conditions (1 kHz frequency, 10% duty cycle) to achieve higher instantaneous brightness without overheating. It is not for continuous DC operation.
• Continuous Forward Current per Segment: 25 mA at 25°C. This is the recommended maximum current for steady-state operation. The derating factor of 0.33 mA/°C indicates that this maximum current must be reduced as the ambient temperature rises above 25°C to prevent overheating.
• Reverse Voltage per Segment: 5 V. Applying a reverse bias voltage higher than this can break down the LED junction.
• Operating & Storage Temperature Range: -35°C to +85°C. The device is rated to function and be stored within this temperature span.
• Soldering Condition: 260°C for 3 seconds, with the iron tip at least 1/16 inch (approx. 1.6 mm) below the seating plane of the component. This is a critical guideline for wave or hand soldering to prevent thermal damage to the LED chips or plastic package.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured under specified test conditions. They are the values designers should use for circuit calculations and performance expectations.

• Average Luminous Intensity per Segment (I_V): 200 μcd (min), 600 μcd (typ) at I_F = 1 mA. This is a measure of the light output. The wide range indicates a binning process; designers must account for the minimum value to ensure sufficient brightness.
• Peak Emission Wavelength (λ_p): 650 nm (typ) at I_F = 20 mA. This is the wavelength at which the spectral output is strongest, placing the color in the hyper-red region of the spectrum.
• Spectral Line Half-Width (Δλ): 20 nm (typ). This indicates the spectral purity or the spread of wavelengths emitted around the peak. A value of 20 nm is typical for AlInGaP red LEDs.
• Dominant Wavelength (λ_d): 639 nm (typ). This is the single wavelength perceived by the human eye that best matches the color of the LED, slightly different from the peak wavelength due to the eye's sensitivity curve.
• Forward Voltage per Segment (V_F): 2.0 V (min), 2.6 V (typ) at I_F = 20 mA. This is the voltage drop across an LED segment when operating. Current-limiting resistors must be calculated using the maximum expected V_F to ensure the current does not exceed limits.
• Reverse Current per Segment (I_R): 100 μA (max) at V_R = 5 V. This is the small leakage current that flows when the LED is reverse-biased within its maximum rating.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (max). This specifies the maximum allowable ratio between the brightest and dimmest segment within a single device, ensuring uniform appearance.

2.3 Binning System Explanation

The datasheet explicitly states the device is \"categorized for luminous intensity.\" This implies a binning or sorting process post-manufacturing. While specific bin codes are not listed here, the practice typically involves grouping displays based on measured light output (e.g., a \"bright\" bin and a \"standard\" bin) to ensure consistency within a production batch. Designers sourcing this component should inquire about available bins if tight brightness uniformity across multiple units is critical for their application. The forward voltage (V_F) range (2.0V to 2.6V) also indicates potential forward voltage binning, which can affect power supply design.

3. Mechanical, Interfacing, and Assembly Information

3.1 Package Dimensions and Pinout

The display is housed in a standard dual-digit LED package. All dimensions are provided in millimeters with a standard tolerance of ±0.25 mm unless otherwise specified. Designers must integrate the precise footprint and height into their PCB and enclosure designs. The pin connection table is essential for correct interfacing. The device uses a multiplexed common cathode configuration: Pin 4 is the common cathode for Digit 1, and Pin 10 is the common cathode for Digit 2. The remaining pins (1, 2, 3, 5, 6, 7, 8, 9, 11, 12, 13, 15, 16, 17, 18, 19, 20) are anodes for the individual segments (A through U, including DP for decimal point). Pin 14 is noted as \"No Connection\" (NC). This configuration allows the two digits to be driven independently using time-division multiplexing, reducing the total number of required driver pins.

3.2 Internal Circuit Diagram and Driving Method

The internal circuit diagram shows the multiplexed common cathode arrangement. All corresponding segment anodes (e.g., all 'A' segments) between the two digits are internally connected. To illuminate a segment on a specific digit, its anode pin must be driven high (with appropriate current limiting), while the cathode of the target digit is pulled low. By rapidly cycling which digit's cathode is active and setting the anodes for the desired pattern, both digits appear to be continuously lit. This method requires a microcontroller or dedicated driver IC capable of multiplexing.

3.3 Soldering and Assembly Guidelines

Strict adherence to the soldering condition (260°C for 3 seconds) is paramount. Exceeding this time or temperature can damage the internal wire bonds, degrade the LED epoxy, or delaminate the package. For reflow soldering, a profile matching this thermal limit must be used. The note about keeping the iron tip below the seating plane helps prevent direct heat transfer to the LED die via the leads. Standard ESD (Electrostatic Discharge) precautions should be observed during handling and assembly to protect the semiconductor junctions.

4. Performance Analysis and Application Considerations

4.1 Typical Characteristic Curves

While the specific graphs are not reproduced in text, typical curves for such a device would include: Forward Current (I_F) vs. Forward Voltage (V_F): This exponential curve shows the relationship between current and voltage. The knee voltage is around 2.0V, after which current increases rapidly with small voltage increases, highlighting the need for current-limiting circuitry. Luminous Intensity (I_V) vs. Forward Current (I_F): This curve is generally linear at lower currents but may saturate at higher currents due to thermal effects. It helps designers choose an operating current to achieve desired brightness efficiently. Luminous Intensity vs. Ambient Temperature: This shows the derating of light output as temperature increases, which is crucial for designs operating in hot environments. Spectral Distribution: A plot showing the intensity of light emitted across wavelengths, centered around 650 nm with a ~20 nm half-width.

4.2 Design Considerations and Application Suggestions

Current Limiting: A series resistor is mandatory for each anode line (or a constant current driver) to set the forward current. The resistor value is calculated as R = (V_supply - V_F) / I_F. Use the maximum V_F (2.6V) from the datasheet to ensure current never exceeds the chosen I_F (e.g., 20 mA) under all conditions. Multiplexing Driver: A microcontroller with sufficient I/O pins or a dedicated LED driver IC (like a MAX7219 or HT16K33) is needed to manage the multiplexing sequence, refresh rate, and brightness control. The refresh rate must be high enough (>60 Hz) to avoid visible flicker. Power Dissipation: Calculate total power: For one segment at 20 mA and 2.6V, P = 52 mW. With multiple segments on, ensure the package's thermal limits are not exceeded, especially at high ambient temperatures. Viewing Angle: The wide viewing angle is beneficial but consider the primary viewing direction when mounting the display in an enclosure to avoid shadows from the bezel.

4.3 Comparison and Common Questions

Comparison with Other Technologies: Compared to 7-segment displays, the 17-segment format allows for a more legible representation of alphabetic characters (A-Z), though not as comprehensive as a dot-matrix display. The AlInGaP technology offers higher efficiency and better temperature stability than older GaAsP or GaP red LEDs. Typical User Questions: Q: Can I drive this display with a constant voltage supply without resistors? A: No. The forward voltage has a range (2.0-2.6V). A constant voltage set for an average V_F could overcurrent an LED with a low V_F, leading to premature failure. Always use current limiting. Q: Why is the peak current (90 mA) higher than the continuous current (25 mA)? A: The LED can handle short, high-current pulses for peak brightness (e.g., for highlighting) because the thermal energy does not have time to build up and damage the junction. The average power must still be within limits. Q: What is the purpose of the \"No Connection\" pin? A> It is often a mechanical placeholder to standardize the pin count with other products in a family or to provide structural symmetry. It must not be connected to any circuit.

5. Technical Principles and Context

5.1 Underlying Technology: AlInGaP on GaAs

The core light-emitting structure is an Aluminum Indium Gallium Phosphide (AlInGaP) heterojunction grown epitaxially on a Gallium Arsenide (GaAs) substrate. By adjusting the ratios of Aluminum, Indium, Gallium, and Phosphorus in the crystal lattice, the bandgap energy—and thus the emitted wavelength—can be precisely tuned. This material system is particularly efficient for producing high-brightness red, orange, and yellow LEDs. The \"Hyper Red\" designation typically refers to a specific composition yielding a deep red color with high luminous efficacy. The GaAs substrate is opaque to the emitted light, so the device structure is designed for top-side emission through the epoxy lens of the package.

5.2 Industry Context and Trends

At the time of this datasheet's release (2003), AlInGaP technology represented a significant advancement over earlier LED materials for red/orange colors. The trend in alphanumeric displays has since moved towards higher-density dot-matrix panels and, more recently, organic LED (OLED) or micro-LED displays for greater flexibility and full-color capability. However, segmented LED displays like this one remain highly relevant for applications requiring extreme reliability, long lifetime, high brightness, simplicity, and low cost in monochromatic or limited-color roles. Their solid-state nature, low power consumption, and excellent readability ensure their continued use in industrial, automotive, and instrumentation fields where these attributes are paramount.