LTC-4624JD LED Display Datasheet - 0.4-inch Digit Height - Hyper Red - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTC-4624JD is a compact, high-performance three-digit numeric display module designed for applications requiring clear, bright numeric readouts. Its core function is to visually represent numbers from 0 to 9 on each of its three digits using individually addressable LED segments.

This device belongs to the category of common anode, multiplexed seven-segment displays. It utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for its light-emitting elements, specifically in a Hyper Red color. The display features a gray faceplate with white segment markings, which enhances contrast and readability under various lighting conditions. The primary design goal is to offer a reliable, low-power, and visually uniform solution for instrument panels, consumer electronics, industrial controls, and other embedded systems where numeric data presentation is critical.

1.1 Key Features and Advantages

• Digit Size: Features a character height of 0.40 inches (10.0 mm), making it suitable for medium-range viewing distances.
• Optical Quality: Provides continuous, uniform light emission across each segment, eliminating dark spots and ensuring consistent character appearance.
• Efficiency: Built with AlInGaP technology, it requires relatively low drive current to achieve high brightness, contributing to lower overall system power consumption.
• Visual Performance: Engineered for high brightness and high contrast against its gray background, resulting in excellent legibility. It also offers a wide viewing angle, making the display readable from various positions.
• Reliability: As a solid-state device, it offers high reliability, long operational lifetime, and resistance to shock and vibration compared to mechanical displays.
• Compliance: The product is constructed as a lead-free package, adhering to RoHS (Restriction of Hazardous Substances) environmental directives.

1.2 Device Identification

The part number LTC-4624JD specifies a device with AlInGaP Hyper Red LEDs in a multiplexed common anode configuration, incorporating a right-hand decimal point. This naming convention allows for clear identification of the technology, color, electrical configuration, and special features.

2. Technical Specifications Deep Dive

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed.

• Power Dissipation per Segment: 70 mW. This is the maximum power that can be safely dissipated by a single LED segment.
• Peak Forward Current per Segment: 90 mA. This is allowed only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent overheating.
• Continuous Forward Current per Segment: 25 mA at 25°C. This rating derates linearly at 0.33 mA/°C as ambient temperature increases above 25°C, meaning the safe continuous current decreases in hotter environments.
• Reverse Voltage per Segment: 5 V. Exceeding this voltage in reverse bias can cause breakdown.
• Operating & Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: Withstands a maximum of 260°C for up to 3 seconds at a distance of 1.6mm below the seating plane during assembly.

2.2 Electrical & Optical Characteristics

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

• Average Luminous Intensity (I_V): Ranges from 200 to 650 µcd at a forward current (I_F) of 1 mA. This indicates the light output power perceived by the human eye.
• Forward Voltage per Segment (V_F): Typically 2.6V, with a maximum of 2.6V at I_F=20mA. Designers must ensure the driving circuit can provide sufficient voltage across this range.
• Peak Emission Wavelength (λ_p): 650 nm. This is the wavelength at which the emitted light intensity is highest, defining its Hyper Red color.
• Dominant Wavelength (λ_d): 639 nm. This is the single-wavelength perception of the color by the human eye.
• Spectral Line Half-Width (Δλ): 20 nm. This parameter describes the spread of the emitted spectrum around the peak wavelength.
• Reverse Current per Segment (I_R): Maximum 100 µA at a reverse voltage (V_R) of 5V.
• Luminous Intensity Matching Ratio: 2:1 maximum. This ensures that the brightness variation between segments within the same display is controlled, providing uniform appearance.

3. Mechanical & Package Information

3.1 Package Dimensions

The LTC-4624JD comes in a standard through-hole DIP (Dual In-line Package) format. All critical dimensions for PCB (Printed Circuit Board) footprint design and panel cutouts are provided in the detailed mechanical drawing. All dimensions are in millimeters with standard tolerances of ±0.25mm unless otherwise specified. Designers must refer to this drawing for accurate spacing of mounting holes, segment window position, and pin spacing to ensure proper mechanical fit.

3.2 Pin Connection and Internal Circuit

The display has a 15-pin configuration (with several pins marked as \"No Pin\"). It uses a multiplexed common anode scheme.

• Common Anodes: Pins 1 (Digit 1), 5 (Digit 2), 7 (Digit 3), and 14 (Common for LEDs L1, L2, L3) are the positive supply terminals for the digits and indicator LEDs.
• Segment Cathodes: Pins 2 (E), 3 (C, L3), 4 (D), 6 (DP), 8 (G), 11 (B, L2), 12 (A, L1), and 15 (F) are the negative terminals for the individual segments and the right-hand decimal point (DP). Segments A-G form the main digit, while L1-L3 are separate indicator LEDs.
• Circuit Diagram: The internal schematic shows that each digit's segments share a common anode connection. To illuminate a specific segment on a specific digit, its corresponding cathode pin must be driven low (grounded) while its digit's common anode pin is driven high. This multiplexing technique reduces the total number of required driver pins.

4. Performance Curve Analysis

The datasheet includes typical characteristic curves which are essential for detailed design analysis.

• Forward Current vs. Forward Voltage (I-V Curve): This curve shows the non-linear relationship between the voltage applied across an LED and the resulting current. It is crucial for designing the current-limiting aspect of the drive circuit, as LEDs are current-driven devices.
• Luminous Intensity vs. Forward Current: This graph illustrates how light output increases with drive current. It is typically linear over a range but will saturate at higher currents. Designers use this to select an operating point that balances brightness with efficiency and lifetime.
• Luminous Intensity vs. Ambient Temperature: This curve demonstrates the derating of light output as the junction temperature of the LED increases. It highlights the importance of thermal management, especially in high-temperature or high-current applications.
• Spectral Distribution: A plot showing the relative intensity of light emitted across different wavelengths, centered around the 650 nm peak. This defines the precise color characteristics of the Hyper Red emission.

5. Application Guidelines & Design Considerations

5.1 Driving Circuit Design

• Constant Current Drive: Highly recommended over constant voltage drive. LEDs are current-sensitive; a constant current source ensures consistent brightness and protects against thermal runaway, even as the forward voltage varies between units or with temperature.
• Voltage Margin: The driver circuit must be designed to accommodate the full range of the LED's forward voltage (V_F), from minimum to maximum, to guarantee the target current is delivered under all conditions.
• Current Limiting: The safe operating current must be selected based on the maximum expected ambient temperature, applying the derating factor of 0.33 mA/°C above 25°C.
• Reverse Bias Protection: The circuit should incorporate protection (e.g., diodes in parallel with the display pins) to prevent the application of reverse voltage or voltage spikes during power cycling, which can cause metal migration and device failure.
• Multiplexing Implementation: Since it's a common anode multiplexed display, a microcontroller or dedicated driver IC must sequentially activate each digit's anode while presenting the segment data for that digit on the cathode lines. The refresh rate must be high enough to avoid visible flicker (typically >60 Hz).

5.2 Thermal & Environmental Management

• Avoid Overstress: Exceeding the recommended drive current or operating temperature will accelerate light output degradation (lumen depreciation) and can lead to premature catastrophic failure.
• Condensation Prevention: Avoid subjecting the display to rapid temperature changes, especially in humid environments, as condensation forming on the LED surface can cause electrical or optical issues.
• Mechanical Handling: Do not apply abnormal force to the display body during assembly. Use appropriate tools and methods to avoid cracking the epoxy lens or damaging the internal wire bonds.

5.3 Assembly & Integration Notes

• Filter/Overlay Films: If using a pressure-sensitive adhesive film (for color filters or patterns), ensure it does not come into forceful contact with the front panel, as this may cause the film to shift from its intended position.
• Binning for Multi-Display Sets: When using two or more displays in one assembly (e.g., a multi-digit panel), it is strongly recommended to source displays from the same production bin to avoid noticeable differences in hue or brightness between units.
• Reliability Testing: If the end product incorporating this display must undergo specific drop or vibration tests, the test conditions should be evaluated in advance to ensure compatibility.

6. Storage & Handling

Proper storage is critical to maintain solderability and performance.

• Standard Storage Conditions: For the through-hole display in its original packaging, the recommended environment is 5°C to 30°C with relative humidity below 60% RH.
• Moisture Sensitivity: If the product is not stored in a moisture-barrier bag or the bag has been open for more than 6 months, it is advised to bake the components at 60°C for 48 hours before use. Assembly should be completed within one week after baking.
• Inventory Management: To prevent pin oxidation, it is suggested to maintain low inventory levels and use components as soon as possible. Prolonged storage under non-ideal conditions may necessitate re-tinning of the leads before soldering.

7. Typical Application Scenarios

The LTC-4624JD is well-suited for a variety of applications requiring clear, reliable numeric indication:

• Test and Measurement Equipment: Digital multimeters, frequency counters, power supplies, where its brightness and readability are key.
• Industrial Controls: Process timers, counter displays, temperature readouts on machinery control panels.
• Consumer Electronics: Audio equipment (amplifier level displays), older model clocks, and appliance controls.
• Automotive Aftermarket: Gauges and diagnostic tools (though not for primary automotive safety systems without prior consultation).
• Embedded Systems & Prototyping: Educational kits and hobbyist projects due to its straightforward multiplexing interface.

8. Frequently Asked Questions (FAQ)

8.1 What is the difference between common anode and common cathode?

In a common anode display, all the anodes (positive sides) of the LEDs for a digit are connected together. You turn on a segment by applying a low voltage (ground) to its cathode. In a common cathode display, the cathodes are common, and you apply a high voltage to the anode to turn on a segment. The LTC-4624JD is a common anode type.

8.2 How do I calculate the current-limiting resistor value?

For a constant voltage drive (not recommended as primary method), use Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet (2.6V) and your desired I_F (e.g., 20mA). If V_supply=5V, R = (5 - 2.6) / 0.02 = 120 Ω. A constant current driver circuit is a more robust solution.

8.3 Why is multiplexing used?

Multiplexing significantly reduces the number of microcontroller I/O pins or driver IC channels required. A non-multiplexed 3-digit, 7-segment display would need 3*7=21 pins. This multiplexed version requires only 3 (digit anodes) + 8 (segment cathodes) = 11 pins, with some shared for indicators.

8.4 What does \"Hyper Red\" mean?

Hyper Red refers to a specific, deep shade of red light emitted by AlInGaP LEDs with a dominant wavelength around 639-650 nm. It is often brighter and more efficient than standard red LEDs and is chosen for its high visibility and contrast.

9. Technology Background and Trends

9.1 AlInGaP Technology

Aluminum Indium Gallium Phosphide (AlInGaP) is a semiconductor material specifically engineered for high-efficiency light emission in the red, orange, and yellow wavelength ranges. Grown on a non-transparent GaAs substrate, it offers superior luminous efficacy and thermal stability compared to older technologies like GaAsP, resulting in the high brightness and reliability seen in the LTC-4624JD.

9.2 Display Technology Context

While seven-segment LED displays like the LTC-4624JD remain a staple for dedicated numeric readouts due to their simplicity, brightness, and low cost, they are part of a broader ecosystem. Dot-matrix LED displays offer alphanumeric and graphic capability. For complex information, LCDs (Liquid Crystal Displays) and OLEDs (Organic Light-Emitting Diodes) are often used. The choice depends on the specific requirements for viewing angle, brightness, power consumption, information complexity, and cost.