LTS-4812SKR-P LED Display Datasheet - 0.39 Inch Digit Height - Super Red - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTS-4812SKR-P is a surface-mount device (SMD) designed for numeric display applications. It is a single-digit display with a character height of 0.39 inches (10.0 mm). The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) epitaxial layers grown on a GaAs substrate to produce Super Red light emission. The device features a gray face with white segments, enhancing contrast and readability. It is constructed as a common anode configuration, which is a standard design for simplifying drive circuitry in multi-segment displays.

1.1 Key Features and Advantages

• Compact Size and High Readability: The 0.39-inch digit height offers a good balance between component footprint and character visibility, suitable for consumer electronics, instrumentation, and control panels.
• Superior Optical Performance: The AlInGaP material system provides high luminous intensity and excellent color purity in the red spectrum. The continuous, uniform segments and wide viewing angle ensure consistent appearance from various perspectives.
• Energy Efficiency: Characterized by low power requirement, making it suitable for battery-powered or energy-conscious applications.
• Enhanced Reliability: As a solid-state device, it offers high reliability and long operational life compared to other display technologies like VFDs or incandescent bulbs.
• Quality Assurance: Devices are categorized (binned) for luminous intensity, allowing for consistent brightness matching in multi-digit displays. The package is lead-free and compliant with RoHS directives.

2. Technical Parameters and Characteristics

This section provides a detailed, objective analysis of the electrical and optical specifications critical for design-in.

2.1 Absolute Maximum Ratings

These are stress limits that must not be exceeded under any conditions to prevent permanent damage.

• Power Dissipation per Segment: 70 mW. This limits the maximum continuous power each LED segment can handle.
• Peak Forward Current per Segment: 90 mA (at 1/10 duty cycle, 0.1ms pulse width). For pulsed operation only.
• Continuous Forward Current per Segment: 25 mA at 25°C. This rating derates linearly at 0.28 mA/°C as ambient temperature (Ta) increases above 25°C. For example, at 85°C, the maximum allowable continuous current would be approximately: 25 mA - ((85°C - 25°C) * 0.28 mA/°C) = 8.2 mA.
• Operating & Storage Temperature Range: -35°C to +105°C.
• Soldering Temperature: 260°C for 3 seconds (iron tip 1/16 inch below seating plane).

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

These are typical operating parameters under specified test conditions.

• Average Luminous Intensity (I_V): 3000 µcd (Typical) at I_F=2mA. The minimum is 1301 µcd and maximum is 8600 µcd, reflecting the binning range.
• Forward Voltage per Chip (V_F): 2.6V (Typical) at I_F=20mA, with a maximum of 2.6V. A current-limiting resistor must be calculated based on this V_F and the supply voltage.
• Peak Emission Wavelength (λ_p): 639 nm. This is the wavelength at which the emitted light intensity is highest.
• Dominant Wavelength (λ_d): 631 nm. This is the single wavelength perceived by the human eye, defining the color point.
• Spectral Line Half-Width (Δλ): 20 nm. This indicates the spectral purity; a smaller value means a more monochromatic light.
• Reverse Current (I_R): 100 µA (Max) at V_R=5V. Note that reverse voltage operation is for test purposes only and not for continuous use.
• Luminous Intensity Matching Ratio: 2:1 (Max). In a multi-digit display, the brightest segment should not be more than twice as bright as the dimmest segment within a similar lit area, ensuring uniformity.
• Crosstalk: ≤ 2.5%. This specifies the maximum unintended illumination of a non-driven segment when an adjacent segment is powered.

2.3 Thermal Considerations

The linear derating of forward current with temperature is a critical design parameter. Exceeding the derated current limit at elevated temperatures can lead to accelerated lumen depreciation and reduced lifespan. Proper PCB layout for heat dissipation is recommended, especially when driving multiple segments or digits simultaneously.

3. Binning System Explanation

The LTS-4812SKR-P is categorized into luminous intensity bins to ensure consistency. The bin code (e.g., J1, K2, M1) indicates the guaranteed minimum and maximum intensity range for that group of devices, measured in microcandelas (µcd) at I_F=2mA with a tolerance of ±15%.

• Lower Bins (J1, J2): 1301-2100 µcd. Suitable for applications where lower brightness is acceptable or power savings are critical.
• Mid-Range Bins (K1, K2, L1): 2101-4300 µcd. Offers a balance of brightness and efficiency for general-purpose displays.
• Higher Bins (L2, M1, M2): 4301-8600 µcd. Designed for high-brightness applications or where superior visibility in high-ambient-light conditions is required.

Specifying a bin code during ordering is essential for applications requiring uniform appearance across multiple units.

4. Performance Curve Analysis

While specific graphs are referenced in the datasheet, their implications are standard for LED devices.

• Forward Current vs. Forward Voltage (I-V Curve): Shows the exponential relationship. The typical V_F of 2.6V at 20mA is the key operating point for driver design.
• Luminous Intensity vs. Forward Current (I-L Curve): Luminous intensity increases with current but not linearly. Efficiency (lumens per watt) typically peaks at a current lower than the absolute maximum rating.
• Luminous Intensity vs. Ambient Temperature: Intensity generally decreases as junction temperature rises. This underscores the importance of thermal management to maintain consistent brightness.
• Spectral Distribution: A plot centered around 639 nm (peak) with a 20 nm half-width, confirming the narrow-band Super Red emission.

5. Mechanical and Package Information

5.1 Package Dimensions and Tolerances

The device conforms to a standard SMD outline. Critical dimensions include the overall length, width, and height, as well as the lead spacing and size. All primary dimensions have a tolerance of ±0.25 mm unless otherwise specified. Key quality notes include limits on foreign material, ink contamination, bubbles within the segment area, and plastic pin burrs.

5.2 Pin Configuration and Circuit Diagram

The display has a 10-pin configuration. It is a common anode device. The internal circuit diagram shows eight individual LED segments (a, b, c, d, e, f, g, dp) with their anodes connected internally to two common anode pins (Pin 3 and Pin 8). Each segment cathode has its own dedicated pin.

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

Polarity Identification: The common anode pins must be connected to the positive supply voltage (through appropriate current-limiting resistors). Individual segments are turned ON by connecting their cathode pins to a lower voltage (typically ground).

5.3 Recommended Soldering Pad Pattern

A land pattern is provided to ensure reliable solder joint formation during reflow. Adhering to this pattern helps prevent tombstoning, misalignment, and insufficient solder fillets.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Instructions

The device is rated for a maximum of two reflow soldering cycles. A complete cool-down to room temperature is required between cycles.

• Profile: Pre-heat: 120-150°C for a maximum of 120 seconds. Peak temperature: 260°C maximum.
• Hand Soldering (Iron): Maximum tip temperature of 300°C for a maximum of 3 seconds per joint. This should be limited to one-time repair only.

6.2 Moisture Sensitivity and Storage

The components are shipped in moisture-proof packaging. They must be stored at ≤30°C and ≤60% Relative Humidity (RH). Once the sealed bag is opened, the components begin to absorb moisture from the environment.

Baking Requirements: If the components are exposed to ambient conditions beyond the specified limits, they must be baked before reflow to prevent popcorn cracking or delamination during the high-temperature soldering process.

• Components in reel: Bake at 60°C for ≥48 hours.
• Components in bulk: Bake at 100°C for ≥4 hours or 125°C for ≥2 hours.

Important: Baking should be performed only once to avoid additional thermal stress.

7. Packaging and Ordering Specifications

7.1 Tape and Reel Packaging

The device is supplied on embossed carrier tape wound onto reels, suitable for automated pick-and-place assembly.

• Reel Dimensions: Standard reel dimensions are provided (e.g., 13-inch or 22-inch reel).
• Carrier Tape: Made from black conductive polystyrene alloy. Dimensions comply with EIA-481-D standards. Key specifications include camber tolerance and cumulative pitch tolerance over 10 sprocket holes.
• Packing Quantities: A 13-inch reel typically contains 800 pieces. A 22-inch reel contains tape length of 44.5 meters. The minimum order quantity for remnants is 200 pieces.
• Orientation: The tape includes a leader and trailer section (minimum 400mm and 40mm, respectively) to facilitate machine loading.

8. Application Suggestions and Design Considerations

8.1 Typical Application Scenarios

• Consumer Electronics: Digital clocks, microwave ovens, air conditioner displays, audio equipment.
• Instrumentation: Panel meters, test equipment, medical device readouts.
• Industrial Controls: Process control indicators, timer displays, counter readouts.
• Automotive Aftermarket: Auxiliary displays where high brightness and wide viewing angle are beneficial.

8.2 Critical Design Considerations

1. Current Limiting: Always use a series resistor for each common anode connection (or each segment if using a constant current driver). Calculate the resistor value based on the supply voltage (V_CC), the typical forward voltage (V_F ~2.6V), and the desired forward current (I_F). Example: For V_CC=5V and I_F=10mA, R = (5V - 2.6V) / 0.01A = 240 Ω.
2. Multiplexing: For multi-digit displays, a multiplexed drive scheme is common. Ensure the peak current in this scheme does not exceed the absolute maximum rating (90mA pulsed) and that the average current respects the derated continuous current limit based on duty cycle and temperature.
3. Thermal Management: Provide adequate copper area on the PCB connected to the thermal pads (if any) or the device leads to act as a heat sink, especially in high-brightness or high-ambient-temperature applications.
4. ESD Protection: Although not explicitly stated as sensitive, standard ESD handling precautions for semiconductor devices are recommended during assembly.
5. Optical Interface: Consider the gray face/white segment design when choosing overlays or filters to maintain optimal contrast.

9. Frequently Asked Questions (Based on Technical Parameters)

9.1 What is the difference between peak wavelength (639nm) and dominant wavelength (631nm)?

Peak wavelength is the physical measurement of the highest intensity point in the emission spectrum. Dominant wavelength is a calculated value that represents the perceived color by the human eye. For a monochromatic source like this red LED, they are close but not identical due to the shape of the eye's sensitivity curve.

9.2 Can I drive this display with a 3.3V microcontroller GPIO pin directly?

No. A typical GPIO pin cannot source or sink enough current (usually 20-25mA max per pin, with a total package limit) to drive multiple LED segments brightly and safely. Furthermore, the LED forward voltage (~2.6V) is close to 3.3V, leaving little headroom for a current-limiting resistor. You must use a driver circuit, such as a transistor array or a dedicated LED driver IC.

9.3 Why is the maximum reflow cycle limited to two?

Multiple reflow cycles subject the plastic package and internal wire bonds to repeated thermal stress, which can potentially lead to mechanical failure, increased moisture absorption, or degradation of the epoxy material. The limit ensures long-term reliability.

9.4 How do I select the appropriate luminous intensity bin?

Choose based on your application's ambient light conditions and required readability. For indoor, low-ambient light, lower bins (J, K) may suffice and be more power-efficient. For sunlight-readable or high-ambient-light applications, specify higher bins (L, M). For multi-digit displays, specifying the same bin code is crucial for uniformity.

10. Technology Background and Trends

10.1 AlInGaP LED Technology

Aluminum Indium Gallium Phosphide (AlInGaP) is a semiconductor material specifically engineered for high-efficiency light emission in the red, orange, and yellow wavelengths. Grown on a GaAs substrate, it offers superior performance compared to older technologies like GaAsP, providing higher brightness, better temperature stability, and longer lifetime. The "Super Red" designation typically indicates a specific composition optimized for high luminous efficacy and a visually saturated red color point.

10.2 SMD LED Display Trends

The trend in display components continues towards miniaturization, higher reliability, and integration. While single-digit SMD displays like the LTS-4812SKR-P remain vital for segmented numeric readouts, there is a parallel growth in dot-matrix SMD displays and fully integrated display modules with embedded controllers. Demands for wider operating temperature ranges, lower power consumption, and compatibility with lead-free and high-temperature soldering processes (like those required for automotive electronics) continue to drive component development.