LTC-2623JS LED Display Datasheet - 0.28-inch Digit Height - AlInGaP Yellow - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTC-2623JS is a quadruple-digit, seven-segment alphanumeric display module designed for applications requiring clear, bright numeric readouts. It utilizes advanced Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor technology on a non-transparent Gallium Arsenide (GaAs) substrate to produce a distinct yellow emission. The display features a gray faceplate with white segment markings, providing high contrast for optimal readability. Its primary design purpose is to offer a reliable, low-power solution for equipment such as instrumentation panels, test equipment, industrial controllers, and consumer electronics where multiple digits need to be displayed in a compact form factor.

1.1 Core Advantages and Target Market

This device is engineered with several key advantages that make it suitable for a wide range of applications. Its high brightness and excellent contrast ratio ensure visibility under various lighting conditions, including bright ambient light. The wide viewing angle allows for readability from off-axis positions, which is crucial for panel-mounted devices. The solid-state construction offers superior reliability and longevity compared to other display technologies, with no moving parts or filaments to fail. The device is categorized for luminous intensity, ensuring consistency in brightness across production batches. Furthermore, it complies with lead-free (RoHS) packaging requirements, making it suitable for modern electronic manufacturing. The target markets include industrial automation, medical devices (where exceptional reliability is confirmed in advance), communication equipment, automotive dashboards (secondary displays), and household appliances.

1.2 Device Configuration

The part number LTC-2623JS specifically denotes an AlInGaP Yellow LED display with a multiplexed common anode configuration. It includes four full digits (0-9) and a right-hand decimal point for each digit, facilitating the display of decimal numbers. The multiplexing scheme is essential for reducing the number of required driver pins, making it more efficient to interface with microcontrollers or dedicated driver ICs.

2. Technical Parameter Deep-Dive

A thorough understanding of the electrical and optical parameters is critical for successful integration into a circuit design.

2.1 Absolute Maximum Ratings

Operating the device beyond these limits may cause permanent damage. The maximum power dissipation per segment is 70 mW. The peak forward current per segment is rated at 60 mA, but this is only permissible under specific pulsed conditions: a 1/10 duty cycle with a 0.1 ms pulse width. The continuous forward current per segment is 25 mA at 25°C, with a derating factor of 0.33 mA/°C. This means the allowable continuous current decreases as the ambient temperature rises above 25°C. The device is rated for an operating and storage temperature range of -35°C to +85°C. The soldering condition specifies that the component body temperature must not exceed its maximum rating during assembly, with a typical reflow profile allowing 3 seconds at 260°C measured 1/16 inch (approximately 1.6 mm) below the seating plane.

2.2 Electrical & Optical Characteristics

These parameters are defined at a standard ambient temperature (Ta) of 25°C. The average luminous intensity per segment (Iv) ranges from 320 µcd (minimum) to 800 µcd (typical) at a forward current (IF) of 1 mA, indicating a bright output. The peak emission wavelength (λp) is 588 nm, and the dominant wavelength (λd) is 587 nm, both measured at IF=20mA, placing the emission firmly in the yellow region of the spectrum. The spectral line half-width (Δλ) is 15 nm, indicating a relatively pure color. The forward voltage per chip (VF) has a typical value of 2.6V with a maximum of 2.6V at IF=20mA, with a minimum noted at 2.05V. Designers must account for this VF range to ensure proper current regulation. The reverse current per segment (IR) is a maximum of 100 µA at a reverse voltage (VR) of 5V. It is crucial to note that this reverse voltage condition is for test purposes only and continuous operation under reverse bias must be avoided. The luminous intensity matching ratio for segments in similar light areas is 2:1 maximum, meaning the dimmest segment should be no less than half as bright as the brightest under the same conditions, ensuring uniform appearance.

3. Binning System Explanation

The datasheet indicates the device is "Categorized for Luminous Intensity." This implies that units are sorted (binned) based on their measured light output at a standard test current. While specific bin codes are not detailed in this excerpt, the practice ensures that designers can select displays with consistent brightness levels. For applications using two or more displays in one assembly, it is strongly recommended to use displays from the same luminous intensity bin to prevent noticeable differences in hue or brightness between units, which can detract from the product's aesthetic and functional quality.

4. Performance Curve Analysis

Typical performance curves are referenced in the datasheet. These graphs are essential for understanding device behavior under non-standard conditions. They typically include the relationship between forward current (IF) and forward voltage (VF), which is non-linear and crucial for driver design. Another vital curve shows luminous intensity versus forward current, demonstrating how light output increases with current but may saturate or degrade at higher levels. A third important curve plots luminous intensity versus ambient temperature, showing the expected decrease in output as temperature rises. These curves allow engineers to optimize the drive conditions for their specific application environment, balancing brightness, power consumption, and device lifetime.

5. Mechanical & Packaging Information

5.1 Package Dimensions and Tolerances

The display has a digit height of 0.28 inches (7.0 mm). All dimensional tolerances are ±0.25 mm unless otherwise specified. Critical mechanical notes include: a pin tip shift tolerance of ±0.4 mm, which must be considered for PCB hole placement; limits on foreign material (≤10 mils), ink contamination (≤20 mils), and bubbles (≤10 mils) within the segment area; and a limit on reflector bending (≤1% of its length). The recommended PCB hole diameter for the pins is 1.0 mm to ensure a proper fit and reliable solder joint.

5.2 Pinout and Polarity Identification

The device has a 16-pin configuration, though not all pins are physically present or electrically connected. It uses a multiplexed common anode scheme. The pin connection is as follows: Pin 1 is the common anode for Digit 1. Pin 8 is the common anode for Digit 4. Pin 11 is the common anode for Digit 3. Pin 14 is the common anode for Digit 2. Pin 12 is a special common anode for the left-side colon segments (L1, L2, L3), if present in the package variant. The segment cathodes are distributed across pins 2 (C, L3), 3 (DP), 5 (E), 6 (D), 7 (G), 13 (A, L1), 15 (B, L2), and 16 (F). Pins 4, 9, and 10 are noted as "No Connection" or "No Pin." An internal circuit diagram would typically show the interconnection of these anodes and cathodes for the four digits.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Parameters

The component is suitable for reflow soldering processes. The critical parameter is that the temperature of the component body itself must not exceed its maximum rated temperature during the soldering process. A specific condition is given: the solder joint area (1/16 inch below the seating plane) can be subjected to 260°C for up to 3 seconds. Designers and process engineers must ensure their reflow profile complies with this requirement to prevent thermal damage to the LED chips or epoxy package.

6.2 Handling and Storage Conditions

To maintain solderability and prevent performance degradation, specific storage conditions are advised. The product should be kept in its original moisture-barrier packaging. The recommended storage environment is between 5°C and 30°C with relative humidity below 60% RH. If the product is removed from its barrier bag or the bag is opened for more than 6 months, a baking procedure of 48 hours at 60°C is recommended before use to remove absorbed moisture and prevent "popcorning" or oxidation during soldering. Prolonged storage of large inventories is discouraged; a "first-in, first-out" (FIFO) consumption policy is suggested.

7. Application Recommendations

7.1 Typical Application Circuits

The multiplexed common anode configuration requires a driver circuit capable of sequentially energizing each digit's common anode while supplying the appropriate segment cathode signals for that digit. This is typically achieved using a microcontroller with sufficient I/O pins or a dedicated LED driver IC with multiplexing support. Constant current driving is highly recommended over constant voltage driving to ensure consistent luminous intensity across segments and digits, independent of forward voltage (VF) variations. The driver circuit must incorporate protection against reverse voltages and transient voltage spikes that can occur during power-up or shutdown sequences, as these can damage the LED chips.

7.2 Critical Design Considerations

Current Limiting: The circuit must be designed to limit the forward current per segment to within the absolute maximum ratings, considering both continuous and pulsed operation. The derating curve for continuous current versus temperature must be respected.
Thermal Management: The operating current should be chosen after considering the maximum ambient temperature of the end application. Excess current at high temperature is a primary cause of accelerated light output degradation and premature failure.
Optical Integration: If a front panel, filter, or diffuser is used, ensure it does not exert mechanical pressure on the display face, especially if a decorative film is applied. Such pressure can cause misalignment or damage.
Environmental Testing: If the end product requires the display to undergo drop or vibration testing, the specific test conditions should be evaluated in advance to ensure compatibility.

8. Technical Comparison & Differentiation

The LTC-2623JS differentiates itself through its use of AlInGaP technology on a GaAs substrate for yellow emission. Compared to older technologies like GaAsP, AlInGaP offers significantly higher luminous efficiency and better temperature stability, resulting in brighter displays with more consistent color over a wide temperature range. The 0.28-inch digit height offers a balance between readability and board space consumption. The multiplexed design reduces interconnect complexity compared to static-drive displays. The inclusion of a right-hand decimal point per digit adds functionality for displaying numerical values. Its lead-free, RoHS-compliant construction aligns with modern environmental regulations.

9. Frequently Asked Questions (FAQ)

Q: Can I drive this display with a 5V microcontroller pin directly?
A: No. The typical forward voltage is 2.6V, but a current-limiting resistor or, preferably, a constant-current driver is required to set the correct current. Connecting directly to 5V would likely destroy the LED segment due to excessive current.

Q: What is the purpose of the "No Connection" pins?
A: They are likely mechanical placeholders to standardize the package footprint with other display variants in the same family that may use those pins for additional features (e.g., a left-hand colon, different decimal points).

Q: How do I calculate the appropriate current-limiting resistor?
A: Use Ohm's Law: R = (V_supply - VF_LED) / I_desired. For a 5V supply, a VF of 2.6V, and a desired current of 10 mA: R = (5 - 2.6) / 0.01 = 240 Ohms. Always use the maximum VF from the datasheet for a conservative design to ensure current doesn't exceed limits if you get a low-VF unit.

Q: Why is reverse bias so dangerous for these LEDs?
A> Applying a reverse voltage can cause metal migration within the semiconductor chip, leading to a permanent increase in leakage current or even a short circuit, rendering the segment inoperative.

10. Design-in Case Study

Consider designing a benchtop digital multimeter display. Four digits are required. The LTC-2623JS is selected for its brightness, contrast, and readability. A microcontroller with a built-in LCD driver is configured in multiplex mode. The driver pins source current to the four common anodes (Digits 1-4) sequentially at a high refresh rate (>60 Hz). The segment cathode pins are connected to current-sinking driver pins. Software controls which segments are lit during each digit's activation period. A constant-current driver IC is placed between the microcontroller and the segment pins to ensure uniform brightness regardless of VF variations. The current is set to 5-8 mA per segment to achieve good brightness while maintaining low power consumption and maximizing display lifespan. Care is taken in the PCB layout to place the display away from heat-generating components like voltage regulators.

11. 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 composition of the AlInGaP alloy determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, yellow (~587 nm). The non-transparent GaAs substrate absorbs any light emitted downward, improving contrast by preventing internal reflections that could "wash out" the segments. The seven segments are individual LED chips wired in the pattern of a digit '8'. By selectively powering different combinations of these segments, all numeric digits and some letters can be formed.

12. Technology Trends

While discrete seven-segment displays remain vital for specific applications, the broader trend is towards integration. This includes the development of displays with integrated driver ICs ("intelligent displays") that simplify microcontroller interfacing. There is also a continuous push for higher efficiency materials, potentially moving from AlInGaP to even more advanced semiconductor compounds for lower voltage operation and higher brightness. Furthermore, the demand for wider color gamuts and customizable designs is being met by surface-mount device (SMD) LED arrays and dot-matrix displays, which offer greater flexibility but with increased driver complexity. The LTC-2623JS represents a mature, optimized solution within the niche of high-reliability, multiplexed numeric displays where simplicity, robustness, and proven performance are paramount.