LTS-3861JR LED Display Datasheet - 0.3-inch Digit Height - 2.6V Forward Voltage - Super Red Color - English Technical Documentation

1. Product Overview

The LTS-3861JR is a single-digit, 7-segment LED display module designed for applications requiring clear, bright numeric readouts. Its primary function is to visually represent numeric characters (0-9) and some limited alphanumeric symbols through the selective illumination of its seven individual segments and an optional decimal point.

The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material for the LED chips. This material system is known for producing high-efficiency red and amber LEDs. The chips are fabricated on a non-transparent GaAs (Gallium Arsenide) substrate, which helps improve contrast by minimizing internal light scattering and reflection. The device features a gray faceplate and white segment color, which enhances the contrast and readability of the illuminated red segments against the background.

The display is categorized for luminous intensity, meaning units are binned or tested to ensure they meet specific brightness criteria, providing consistency in performance for production batches.

1.1 Key Features and Advantages

• Compact Size: Features a 0.3-inch (7.62 mm) digit height, making it suitable for space-constrained panels and devices.
• Optical Quality: Offers continuous uniform segments for a smooth, professional character appearance without gaps or irregularities.
• High Performance: Delivers high brightness and high contrast, ensuring excellent visibility.
• Wide Viewing Angle: Provides clear readability from a broad range of perspectives.
• Low Power Consumption: Designed with low power requirements, making it energy-efficient.
• Reliability: Benefits from solid-state reliability with no moving parts, leading to long operational life.

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 outside these limits is not advised.

• Power Dissipation per Segment: 70 mW maximum. This is the maximum power that can be safely dissipated as heat by a single LED segment.
• Peak Forward Current per Segment: 90 mA maximum. 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 maximum at 25°C. This current must be derated linearly by 0.33 mA/°C as the ambient temperature (Ta) rises above 25°C.
• Reverse Voltage per Segment: 5 V maximum. Exceeding this can break down the LED's PN junction.
• Operating Temperature Range: -35°C to +85°C.
• Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm (1/16 inch) below the seating plane of the component.

2.2 Electrical & Optical Characteristics

These parameters are measured at an ambient temperature (Ta) of 25°C and define the typical operating performance.

• Average Luminous Intensity (I_V): Ranges from 200 μcd (min) to 600 μcd (max) at a forward current (I_F) of 1 mA. This is the measure of perceived brightness by the human eye.
• Peak Emission Wavelength (λ_p): Typically 639 nm at I_F=20mA. This is the wavelength at which the optical output power is greatest.
• Spectral Line Half-Width (Δλ): Typically 20 nm at I_F=20mA. This indicates the spectral purity; a smaller value means a more monochromatic color.
• Dominant Wavelength (λ_d): Typically 631 nm at I_F=20mA. This is the single wavelength perceived by the human eye, defining the color (super red).
• Forward Voltage per Segment (V_F): Ranges from 2.0 V (min) to 2.6 V (max) at I_F=20mA. This is the voltage drop across the LED when operating.
• Reverse Current per Segment (I_R): Maximum 100 μA at a reverse voltage (V_R) of 5V. This is the small leakage current when the LED is reverse-biased.
• Luminous Intensity Matching Ratio (I_V-m): Maximum 2:1 at I_F=1mA. This specifies the maximum allowable brightness variation between different segments within a single device, ensuring uniform appearance.

Note: Luminous intensity measurement follows the CIE (Commission Internationale de l'Eclairage) eye-response curve standard.

3. Binning and Categorization System

The LTS-3861JR employs a categorization system primarily for Luminous Intensity. This means during manufacturing, devices are tested and sorted into different bins or categories based on their measured brightness at a standard test current (typically 1mA or 20mA). This allows designers to select parts with consistent brightness levels for their applications, preventing noticeable variations in display intensity across multiple digits in a multi-digit display. The datasheet specifies a range (200-600 μcd), and products are guaranteed to fall within specified sub-ranges within this.

4. Performance Curve Analysis

The datasheet references typical characteristic curves which are crucial for design. While not displayed in the provided text, standard curves for such a device would include:

• Forward Current vs. Forward Voltage (I_F-V_F Curve): Shows the exponential relationship. Essential for designing the current-limiting circuitry.
• Luminous Intensity vs. Forward Current (I_V-I_F Curve): Shows how brightness increases with current, typically in a near-linear relationship within the operating range before efficiency drops.
• Luminous Intensity vs. Ambient Temperature (I_V-T_a Curve): Illustrates the decrease in light output as junction temperature rises, highlighting the importance of thermal management and current derating.
• Spectral Distribution: A graph showing the relative optical power across wavelengths, centered around the 639 nm peak, with a width defined by the 20 nm half-width.

5. Mechanical and Package Information

5.1 Physical Dimensions

The device has a defined package outline. All dimensions are provided in millimeters (mm) with standard tolerances of ±0.25 mm unless otherwise specified. Key dimensions include the overall height, width, and depth of the package, the digit window size, and the spacing between the segments.

5.2 Pin Configuration and Internal Circuit

The LTS-3861JR is a common anode device. This means the anodes of all LED segments (A-G and DP) are connected internally and brought out to common pins (Pin 1 and Pin 6). Each segment's cathode is brought out to an individual pin. To illuminate a segment, its corresponding cathode pin must be driven to a low logic level (ground) while the common anode pin is held at a positive voltage (through a current-limiting resistor).

Pin Connection Table:
1: Common Anode
2: Cathode F
3: Cathode G
4: Cathode E
5: Cathode D
6: Common Anode
7: Cathode D.P. (Decimal Point)
8: Cathode C
9: Cathode B
10: Cathode A

The internal circuit diagram shows the electrical interconnection of the 7 segments (A, B, C, D, E, F, G) and the decimal point (DP) with the two common anode nodes.

6. Soldering and Assembly Guidelines

Adherence to soldering specifications is critical to prevent damage.

• Reflow Soldering: The maximum allowable solder temperature is 260°C. The component should be exposed to this peak temperature for no more than 3 seconds. The temperature is measured at a point 1.6mm below the body of the component (the seating plane on the PCB).
• Hand Soldering: If hand soldering is necessary, a temperature-controlled iron should be used, and contact time with each pin should be minimized to prevent excessive heat transfer to the LED chip.
• Storage Conditions: Devices should be stored within the specified storage temperature range of -35°C to +85°C in a dry environment to prevent moisture absorption, which can cause \"popcorning\" during reflow.

7. Application Suggestions

7.1 Typical Application Scenarios

• Test and Measurement Equipment: Digital multimeters, oscilloscopes, power supplies.
• Consumer Electronics: Audio amplifiers, clock radios, kitchen appliances.
• Industrial Controls: Panel meters, process indicators, timer displays.
• Automotive Aftermarket: Gauges and display modules (consider extended temperature requirements).

7.2 Design Considerations

• Current Limiting: A series resistor is mandatory for each common anode connection to limit the current through the segments. The resistor value (R) is calculated using: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet for a safe design.
• Multiplexing: For multi-digit displays, a multiplexing technique is used where digits are illuminated one at a time rapidly. The peak current per segment can be higher (up to the 90mA pulsed rating) to compensate for the reduced duty cycle, achieving higher perceived brightness.
• Driver Circuits: Use dedicated LED driver ICs or microcontroller GPIO pins with sufficient current sink/source capability. For common anode, the driver must sink current (connect to ground).
• Viewing Angle: The wide viewing angle is beneficial but consider the final mounting orientation relative to the user.

8. Technical Comparison and Differentiation

The LTS-3861JR differentiates itself primarily through its use of AlInGaP technology compared to older GaAsP or standard GaP LEDs. Key advantages include:

• Higher Efficiency and Brightness: AlInGaP LEDs provide significantly higher luminous intensity for the same drive current.
• Better Color Saturation: The \"super red\" color is more vibrant and pure compared to standard red LEDs.
• Improved Temperature Stability: AlInGaP generally exhibits less variation in wavelength and intensity with temperature changes compared to some older technologies.
• The 0.3-inch digit height offers a balance between readability and board space, fitting between smaller 0.2-inch and larger 0.5-inch or 0.56-inch displays.

9. Frequently Asked Questions (FAQ)

Q1: What is the difference between \"peak wavelength\" and \"dominant wavelength\"?
A1: Peak wavelength is where the optical power output is physically highest. Dominant wavelength is the single wavelength that would produce the same color perception to the human eye. For LEDs, they are often close but not identical due to the shape of the emission spectrum.

Q2: Can I drive this display directly from a 5V microcontroller pin?
A2: No. You must use a current-limiting resistor. Connecting it directly would likely exceed the maximum continuous current (25mA) and destroy the LED. Calculate the resistor value based on your supply voltage (e.g., 5V), the LED forward voltage (~2.6V max), and your desired operating current (e.g., 10-20mA).

Q3: Why are there two common anode pins (Pin 1 and Pin 6)?
A3> This is a common design for mechanical and electrical symmetry. It helps distribute current more evenly and provides flexibility in PCB routing. Internally, they are connected. You can use either one or connect both to your positive supply.

Q4: How do I calculate the power dissipation for thermal design?
A4> For a single segment: P_d = V_F * I_F. For example, at I_F=20mA and V_F=2.5V, P_d = 50mW, which is below the 70mW maximum. In a multiplexed display with multiple segments on, calculate for the worst-case scenario (e.g., digit \"8\" with all 7 segments lit).

10. Design and Usage Case Study

Scenario: Designing a 4-Digit Voltmeter Display.
A designer is creating a compact voltmeter module. They select four LTS-3861JR displays. To save I/O pins on the microcontroller, they wire the displays in a multiplexed configuration: all corresponding segment cathodes (A, B, C,...) are connected together across the four digits. Each digit's common anode is controlled by a separate transistor switch. The microcontroller cycles through turning on one digit's anode at a time while outputting the segment pattern for that digit. To maintain brightness with a 1/4 duty cycle, the segment current during its active time is increased, but kept within the pulsed current rating. Current-limiting resistors are placed on the common anode lines (before the transistors). The AlInGaP technology ensures the display remains clearly readable even in moderately bright ambient light.

11. Technology Principle Introduction

An LED (Light Emitting Diode) is a semiconductor diode. When forward-biased, electrons from the n-type region recombine with holes from the p-type region in the active layer. This recombination releases energy in the form of photons (light). The specific wavelength (color) of the light is determined by the bandgap energy of the semiconductor material. AlInGaP is a compound semiconductor whose bandgap can be tuned by adjusting the ratios of Aluminum, Indium, Gallium, and Phosphorus to produce light in the red, orange, and amber spectrum. The \"super red\" designation indicates a specific, high-purity red color point. The non-transparent GaAs substrate absorbs stray light, improving contrast by preventing it from reflecting back through the chip and washing out the dark (off) state of the segments.

12. Technology Trends and Evolution

While discrete 7-segment displays like the LTS-3861JR remain relevant for specific applications, broader trends in display technology include:

• Integration: Movement towards multi-digit modules with integrated driver ICs, simplifying the interface for microcontrollers (e.g., SPI or I2C communication).
• Material Advancements: Ongoing research into materials like GaN (for blue/green/white) and improvements in AlInGaP and InGaN (for red) continue to push efficiency (lumens per watt) and reliability higher.
• Alternative Technologies: In many consumer applications, dot-matrix OLED or LCD displays are replacing segmented LEDs due to their flexibility in displaying graphics and text. However, segmented LEDs retain strong advantages in applications requiring very high brightness, wide viewing angles, extreme simplicity, and low cost for numeric-only displays.
• Miniaturization: There is a constant drive for smaller pixel pitches and higher density, though the 0.3-inch size remains a standard for many instrument panels due to readability requirements.