LTC-4624JS LED Display Datasheet - 0.4 Inch Digit Height - AlInGaP Yellow - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTC-4624JS is a 0.4-inch (10.0 mm) digit height, triple-digit, seven-segment LED display module. This device utilizes AlInGaP (Aluminum Indium Gallium Phosphide) yellow LED chips, which are fabricated on a non-transparent GaAs substrate. The display features a gray face with white segments, providing high contrast for optimal readability. It is designed as a multiplex common anode display, making it suitable for applications where minimizing the number of required driver pins is essential.

1.1 Key Features

• 0.4 inch (10.0 mm) Digit Height
• Continuous Uniform Segments
• Low Power Requirement
• Excellent Character Appearance
• High Brightness & High Contrast
• Wide Viewing Angle
• Solid State Reliability
• Categorized for Luminous Intensity
• Lead-Free Package (RoHS Compliant)

1.2 Device Identification

The part number LTC-4624JS specifically denotes an AlInGaP Yellow, multiplex common anode display with a right-hand decimal point.

2. Mechanical and Package Information

2.1 Package Dimensions

The display's physical dimensions are provided in a detailed drawing. All primary dimensions are specified in millimeters. Key tolerances and notes include:

• General dimensional tolerance: ±0.25 mm unless otherwise specified.
• Pin tip shift tolerance: ±0.4 mm.
• Limits for foreign material, ink contamination, and bubbles within the segment area.
• Bending of the reflector is limited to 1% of its length.
• A PCB hole diameter of 1.0 mm is recommended for best fit.

3. Electrical Configuration

3.1 Internal Circuit Diagram

The display incorporates a multiplexed common anode configuration. The three digit anodes (Digit 1, Digit 2, Digit 3) and a common anode for the right-hand decimal points (L1, L2, L3) are separate, allowing for time-division multiplexing control.

3.2 Pin Connection and Function

The device has a 15-pin configuration (with several No Connection pins). The pinout is as follows:

• Pin 1: COMMON ANODE DIGIT 1
• Pin 2: CATHODE E
• Pin 3: CATHODE C, L3
• Pin 4: CATHODE D
• Pin 5: COMMON ANODE DIGIT 2
• Pin 6: CATHODE DP (Decimal Point)
• Pin 7: COMMON ANODE DIGIT 3
• Pin 8: CATHODE G
• Pin 9, 10, 13: NO PIN / No Connection
• Pin 11: CATHODE B, L2
• Pin 12: CATHODE A, L1
• Pin 14: COMMON ANODE L1, L2, L3 (Decimal Points)
• Pin 15: CATHODE F

4. Ratings and Characteristics

4.1 Absolute Maximum Ratings (Ta=25°C)

• Power Dissipation Per Segment: 70 mW
• Peak Forward Current Per Segment (1/10 Duty, 0.1ms Pulse): 60 mA
• Continuous Forward Current Per Segment: 25 mA (Derating linearly from 25°C at 0.33 mA/°C)
• Operating Temperature Range: -35°C to +85°C
• Storage Temperature Range: -35°C to +85°C
• Solder Condition: 260°C for 3 seconds, 1/16 inch below seating plane.

4.2 Electrical & Optical Characteristics (Ta=25°C)

• Average Luminous Intensity Per Segment (I_V): Min 200, Typ 650, Max – µcd (Test Condition: I_F=1mA)
• Peak Emission Wavelength (λ_p): 588 nm (I_F=20mA)
• Spectral Line Half-Width (Δλ): 15 nm (I_F=20mA)
• Dominant Wavelength (λ_d): 587 nm (I_F=20mA)
• Forward Voltage Per Chip (V_F): Typ 2.05V, Max 2.6V (I_F=20mA)
• Reverse Current Per Segment (I_R): Max 100 µA (V_R=5V)
• Luminous Intensity Matching Ratio: Max 2:1 (I_F=1mA)

Notes: Luminous intensity is measured with a CIE eye-response filter. Reverse voltage is for test only and not for continuous operation. Cross-talk specification is ≤ 2.5%.

4.3 Typical Performance Curves

The datasheet includes typical curves illustrating the relationship between forward current and luminous intensity, forward voltage, and the effects of ambient temperature. These curves are essential for designers to optimize drive current for desired brightness while maintaining reliability across the operating temperature range.

5. Application Guidelines and Cautions

5.1 Design and Usage Considerations

• Intended Use: For ordinary electronic equipment (office, communications, household). Consultation is required for safety-critical applications (aviation, medical, etc.).
• Ratings Compliance: Adherence to Absolute Maximum Ratings is mandatory to prevent damage.
• Current and Temperature: Exceeding recommended drive current or operating temperature can cause severe light output degradation or premature failure.
• Circuit Protection: The driving circuit must protect LEDs from reverse voltages and transient spikes during power cycling.
• Constant Current Drive: Recommended for consistent luminous performance.
• Forward Voltage Range: Circuit design must accommodate the full V_F range (2.05V to 2.6V) to ensure the target current is always delivered.
• Thermal Derating: Select operating current based on maximum ambient temperature.
• Avoid Reverse Bias: Can cause metal migration, increasing leakage current or causing shorts.
• Condensation: Avoid rapid temperature changes in humid environments to prevent condensation on the display.
• Mechanical Handling: Do not apply abnormal force to the display body during assembly.
• Pattern Film: If a decorative film is applied, avoid direct contact with the front panel to prevent shifting.
• Binning for Multi-Displays: Use displays from the same luminous intensity bin when assembling multiple units to ensure uniform appearance.
• Drop/Vibration Testing: Share test conditions for evaluation prior to testing.

5.2 Storage and Handling

• Standard Storage: Product in original packaging. Temperature: 5°C to 30°C. Humidity: Below 60% RH.
• Consequences of Improper Storage: Pin oxidation may occur, requiring re-plating before use.
• Inventory Management: Consume inventory promptly. Avoid long-term storage of large quantities.
• Moisture Sensitivity: If the moisture barrier bag is opened for >6 months, bake at 60°C for 48 hours and assemble within one week.

6. Technical Deep Dive and Analysis

6.1 Photometric and Colorimetric Analysis

The use of AlInGaP technology for yellow emission offers advantages over traditional phosphor-converted yellow LEDs, including potentially higher efficiency and better color stability over temperature and time. The dominant wavelength of 587 nm places it in the pure yellow region of the spectrum. The narrow spectral half-width (15 nm) is characteristic of direct semiconductor emission, resulting in a saturated color.

6.2 Electrical Parameter Interpretation

The forward voltage (V_F) is relatively low for an AlInGaP LED, typically around 2.05V at 20mA. Designers must ensure the power supply can provide sufficient voltage, especially when multiplexing, considering the voltage drop across the driver circuitry. The derating curve for continuous current is critical; at an ambient temperature of 85°C, the maximum allowable continuous current drops significantly from the 25mA rating at 25°C.

6.3 Binning and Matching

The display is categorized (binned) for luminous intensity. The matching ratio of 2:1 means the dimmest segment in a batch should be no less than half as bright as the brightest. For multi-digit assemblies, specifying the same bin code is crucial for visual uniformity, preventing some digits from appearing brighter than others.

7. Application Scenarios and Design Notes

7.1 Typical Applications

The LTC-4624JS is well-suited for instrument panels, industrial control readouts, test and measurement equipment, point-of-sale terminals, and appliance displays where a clear, bright, multi-digit numeric readout is required. Its multiplexed design reduces microcontroller I/O pin requirements.

7.2 Driver Circuit Design

A typical driver involves a microcontroller with segment drivers (e.g., 74HC595 shift register with current-limiting resistors) and digit drivers (e.g., PNP transistors or dedicated sink drivers). The multiplexing frequency should be high enough (>60Hz) to avoid flicker. Constant current drivers (integrated LED driver ICs) are strongly recommended over simple resistor limiting for stable brightness across units and temperatures.

7.3 Thermal Management Considerations

While the display itself has no defined thermal resistance parameter, board layout should ensure adequate airflow, especially if operating near maximum ratings. The power dissipation per segment is limited to 70mW. At the maximum continuous current, the actual dissipation must be calculated (V_F * I_F) and kept within this limit, considering derating with temperature.

8. Comparison and Differentiation

Compared to older technologies like standard GaP yellow LEDs, AlInGaP offers significantly higher brightness and efficiency. Versus contemporary white LEDs with filters, it provides a purer spectral color and often higher efficacy for monochromatic yellow light. The through-hole package offers mechanical robustness and ease of hand-soldering for prototyping, contrasting with surface-mount alternatives that save board space.

9. Frequently Asked Questions (FAQ)

Q: Can I drive this display with a 5V microcontroller directly?
A: No. You must use current-limiting resistors or, preferably, constant-current drivers. The forward voltage is ~2.05V, so a resistor is needed to drop the remaining voltage (e.g., 5V - 2.05V = 2.95V) and set the current. At 20mA, R = 2.95V / 0.02A = 147.5Ω (use 150Ω).

Q: What is the purpose of the separate anodes for digits and decimal points?
A: It allows independent control. You can illuminate Digit 1, Digit 2, and Digit 3 sequentially (multiplexing) using their individual anodes, while the segment cathodes are common. The decimal point anode is also separate, allowing you to turn on/off the decimal point for each digit independently during its multiplexed time slot.

Q: How do I achieve uniform brightness when multiplexing?
A: Since each digit is only on for a fraction of the time (e.g., 1/3 duty cycle for 3 digits), the peak current during its \"on\" time must be higher to achieve the same average brightness as a statically driven digit. If the target average current is 5mA, the peak current during the multiplex pulse should be approximately 5mA * (Number of Digits) = 15mA (for a 1/3 duty cycle).

Q: The datasheet mentions \"Lead-Free Package.\" What are the soldering implications?
A: Lead-free solder typically has a higher melting point than traditional tin-lead solder. The specified soldering condition of 260°C for 3 seconds aligns with common lead-free reflow profiles. Ensure your assembly process meets this requirement to avoid thermal damage.