LED Display LTS-3361JR Specification - 0.3-inch (7.62mm) Digit Height - Super Red - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-3361JR is a 0.3-inch (7.62 mm) digit height numeric LED display module. It is designed for applications requiring clear, bright numeric readouts. The device utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology to produce a Super Red color output. The display features a light gray face with white segments, providing high contrast for excellent readability. It is constructed as a common cathode type device, meaning all the cathodes of the LEDs for each digit segment are connected together internally.

1.1 Core Features and Advantages

The LTS-3361JR offers several key advantages for electronic design:

• Compact Size with High Visibility: The 0.3-inch digit height provides a good balance between compact footprint and clear character appearance.
• Superior Optical Performance: The use of AlInGaP chips results in high brightness and excellent contrast ratio. The light gray face further enhances contrast against the illuminated red segments.
• Wide Viewing Angle: The display is designed to be legible from a broad range of angles, making it suitable for various mounting positions.
• Low Power Consumption: It has a low power requirement per segment, contributing to energy-efficient designs.
• High Reliability: As a solid-state device, it offers long operational life and robustness against vibration and shock compared to mechanical displays.
• RoHS Compliance: The device is supplied in a lead-free package, adhering to environmental regulations.

1.2 Target Applications

This LED display is intended for use in ordinary electronic equipment. Typical application areas include, but are not limited to, office automation equipment, communication devices, household appliances, instrumentation panels, and consumer electronics where numeric indication is required. It is suitable for applications where reliability, clarity, and compact size are important design considerations.

2. Technical Specifications and Objective Interpretation

2.1 Absolute Maximum Ratings

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

• Power Dissipation per Segment: 70 mW. This is the maximum allowable power that can be dissipated as heat by a single segment LED chip.
• Peak Forward Current per Segment: 90 mA. This current is permissible 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 by 0.33 mA/°C as ambient temperature (Ta) increases above 25°C. For example, at 50°C, the maximum continuous current would be approximately 25 mA - (0.33 mA/°C * 25°C) = 16.75 mA.
• Operating & Storage Temperature Range: -35°C to +85°C. The device can be stored and operated within this full range.
• Solder Conditions: Wave soldering at 260°C for 3 seconds, measured 1/16 inch (approx. 1.6mm) below the seating plane of the package.

2.2 Electrical & Optical Characteristics

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

• Average Luminous Intensity (I_V): 200-600 μcd (microcandelas) at I_F=1mA. This indicates the light output per segment. The wide range suggests a binning system for intensity.
• Peak Emission Wavelength (λ_p): 639 nm (typical). This is the wavelength at which the spectral output is strongest, in the red region of the spectrum.
• Dominant Wavelength (λ_d): 631 nm (typical). This is the single wavelength perceived by the human eye, defining the color hue as \"Super Red\".
• Spectral Line Half-Width (Δλ): 20 nm (typical). This measures the spectral purity; a narrower width indicates a more monochromatic color.
• Forward Voltage per Chip (V_F): 2.0V to 2.6V at I_F=20mA. Designers must ensure the driving circuit can accommodate this voltage range to deliver the desired current.
• Reverse Current (I_R): 100 μA (max) at V_R=5V. This parameter is for test purposes only; continuous reverse bias operation is prohibited.
• Luminous Intensity Matching Ratio: 2:1 (max). This specifies the maximum allowable variation in brightness between segments within the same digit to ensure uniform appearance.
• Cross Talk: ≤2.5%. This defines the maximum amount of unintended light leakage from an unpowered segment when adjacent segments are lit.

3. Mechanical and Package Information

3.1 Package Dimensions

The display conforms to a standard 10-pin DIP (Dual In-line Package) 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.
• Quality control criteria limit foreign material on segments to ≤10 mils, bending of the reflector to ≤1% of its length, bubbles in segments to ≤10 mils, and ink contamination on the surface to ≤20 mils.

3.2 Pin Configuration and Polarity

The device has a 10-pin configuration with two common cathode pins. The internal circuit diagram shows a common cathode arrangement for the 7-segment plus decimal point display. The pin connection is as follows:

• Pin 1: Common Cathode
• Pin 2: Anode for Segment F
• Pin 3: Anode for Segment G
• Pin 4: Anode for Segment E
• Pin 5: Anode for Segment D
• Pin 6: Common Cathode
• Pin 7: Anode for Decimal Point (DP)
• Pin 8: Anode for Segment C
• Pin 9: Anode for Segment B
• Pin 10: Anode for Segment A

Pin 1 is marked as \"No Connection\" in the diagram, but the table clarifies it is a Common Cathode. Pins 1 and 6 are internally connected as the common cathode points.

4. Application Guidelines and Design Considerations

4.1 Critical Application Cautions

Adherence to these guidelines is crucial for reliable operation:

• Drive Circuit Design: Constant current driving is strongly recommended over constant voltage to ensure consistent luminous intensity across units and over temperature variations. The circuit must be designed to supply the intended current across the full V_F range (2.0V-2.6V).
• Current and Thermal Management: Exceeding the absolute maximum ratings for current or operating temperature will accelerate light output degradation and can cause premature failure. The drive current must be derated appropriately for high ambient temperatures.
• Protection Against Electrical Stress: The driving circuit should incorporate protection against reverse voltages and transient voltage spikes during power-up or shutdown to prevent damage.
• Avoiding Reverse Bias: Continuous or significant reverse bias must be avoided as it can induce metal migration within the LED chip, leading to increased leakage current or short-circuit failure.
• Environmental Considerations: Rapid temperature changes in humid environments should be avoided to prevent condensation on the display, which could lead to electrical or optical issues.
• Mechanical Handling: Do not apply abnormal force to the display body during assembly. If using a front-application film, avoid having it in direct contact with the front panel/cover as external force may shift it.
• Binning for Multi-Digit Displays: When assembling two or more displays in one unit, it is recommended to use displays from the same production bin to avoid noticeable differences in hue or brightness between digits.

4.2 Storage and Handling Conditions

Proper storage is essential to maintain solderability and performance:

• Standard Storage (Unopened Package): Temperature: 5°C to 30°C. Relative Humidity: Below 60% RH. Product should be kept in its original packaging.
• Consequences of Improper Storage: Prolonged storage outside these conditions, especially high humidity, can lead to oxidation of the component leads (pins), requiring re-plating before use.
• Inventory Management: It is advised to consume inventory promptly and avoid long-term storage of large quantities.
• Post-Exposure Procedure: If the factory-sealed bag has been opened for more than 6 months, it is recommended to bake the components at 60°C for 48 hours to remove moisture and then complete assembly within one week. This aligns with MSL (Moisture Sensitivity Level) precautions.

5. Performance Analysis and Typical Curves

The datasheet references typical performance curves which are essential for detailed design analysis. While the specific graphs are not detailed in the provided text, they typically include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph shows how light output increases with drive current. It is typically non-linear, emphasizing the benefit of constant current drive.
• Forward Voltage vs. Forward Current: Illustrates the relationship between voltage and current, highlighting the need for a current-limiting mechanism in the driver circuit.
• Relative Luminous Intensity vs. Ambient Temperature: Shows how light output decreases as the junction temperature of the LED increases. This curve is critical for thermal management and current derating calculations.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at ~639nm and the spectral width.

Designers should consult the full datasheet graphs to accurately model the display's behavior under their specific operating conditions.

6. Comparison and Selection Guidance

6.1 Key Differentiators

The LTS-3361JR's primary differentiators in its category are its use of AlInGaP technology for Super Red color and its specific mechanical package with a light gray face. Compared to older GaAsP or GaP red LEDs, AlInGaP offers significantly higher brightness and efficiency. The light gray face, as opposed to black or dark gray, provides a higher contrast background when the segments are unlit, improving overall display aesthetics in various lighting conditions.

6.2 Common Design Questions

Q: Can I drive this display directly from a microcontroller pin?

A: No. A typical MCU pin cannot source or sink the required current (up to 25mA per segment, potentially much more for multiple segments on a common pin) and would likely be damaged. An external driver circuit (e.g., using transistor arrays or dedicated LED driver ICs) is necessary.

Q: Why is constant current drive recommended?

A: LED brightness is primarily a function of current, not voltage. The forward voltage (V_F) has a tolerance and varies with temperature. A constant current source ensures consistent brightness across all units and over the operating temperature range, regardless of V_F variations.

Q: What is the purpose of having two common cathode pins (1 and 6)?

A> This is typically for current distribution and mechanical symmetry. Connecting both pins to the common ground helps balance the current load and can provide a more robust electrical connection.

7. Practical Application Example

Scenario: Designing a simple 3-digit voltmeter display.

Three LTS-3361JR displays would be used. A microcontroller with an ADC measures the voltage. The microcontroller's firmware contains a look-up table to convert the digital reading into the appropriate segment patterns for each digit (including the decimal point). The microcontroller outputs are connected to the anodes of each segment via current-limiting resistors or, more ideally, a constant-current LED driver IC. The common cathode pins of all three displays would be connected together and switched to ground by the microcontroller (or a driver IC) in a multiplexed fashion. Multiplexing rapidly cycles through illuminating each digit one at a time, reducing the number of required driver pins. The design must ensure the peak current during the multiplexing pulse does not exceed the absolute maximum rating and that the average current meets the desired brightness level. Thermal considerations for the driver IC and the display itself in the enclosure must also be evaluated.