LTS-3861JD 0.3-inch Hyper Red LED Display Datasheet - Digit Height 7.62mm - Forward Voltage 2.6V - Power 70mW - English Technical Document

1. Product Overview

The LTS-3861JD is a compact, single-digit, seven-segment display designed for applications requiring clear numeric indication with low power consumption. Its core function is to provide a highly legible numeric readout. The device utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology, specifically Hyper Red chips grown on a GaAs substrate. This technology choice is fundamental to achieving its key performance characteristics of high brightness and efficiency within the red spectrum. The visual design features a light gray face with white segments, which is a deliberate choice to enhance contrast and improve readability under various lighting conditions. The product is categorized as a low-current display, making it suitable for battery-powered or energy-conscious electronic systems.

1.1 Features and Core Advantages

The display incorporates several design features that contribute to its performance and reliability:

• 0.30 Inch Digit Height (7.62 mm): Provides a standard, easily readable character size for panel meters, instrumentation, and consumer electronics.
• Continuous Uniform Segments: Ensures consistent illumination across each segment, leading to a professional and clean character appearance without dark spots or irregularities.
• Low Power Requirement: Engineered for efficiency, allowing operation in circuits where power budget is a critical constraint.
• Excellent Character Appearance & High Contrast: The combination of Hyper Red emission, light gray face, and white segments yields sharp, well-defined numerals.
• High Brightness: The AlInGaP material system is known for its high luminous efficiency, resulting in bright output even at lower drive currents.
• Wide Viewing Angle: The package and chip design facilitate visibility from a broad range of angles, which is essential for displays that may be viewed off-axis.
• Solid-State Reliability: As an LED-based device, it offers long operational life, shock resistance, and no moving parts, unlike mechanical displays.
• Categorized for Luminous Intensity: Units are binned or tested for light output consistency, aiding in design where uniform brightness across multiple digits is required.
• Lead-Free Package (RoHS Compliant): Manufactured in accordance with environmental regulations restricting hazardous substances.

1.2 Device Identification

The part number LTS-3861JD specifically denotes a device with AlInGaP Hyper Red chips in a common anode configuration, featuring a right-hand decimal point. This naming convention allows designers to precisely select the desired color, polarity, and optional features.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed, objective analysis of the electrical and optical parameters specified in the datasheet. Understanding these values is critical for proper circuit design and ensuring long-term reliability.

2.1 Absolute Maximum Ratings

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

• Power Dissipation per Segment: 70 mW. This is the maximum allowable power that can be dissipated as heat by a single LED segment under continuous DC operation. Exceeding this can lead to overheating and accelerated degradation of the semiconductor material.
• Peak Forward Current per Segment: 90 mA (at 1/10 duty cycle, 0.1ms pulse width). This rating is for pulsed operation only. The short pulse width and low duty cycle prevent significant heat buildup, allowing a higher instantaneous current than the DC rating.
• Continuous Forward Current per Segment: 25 mA (at 25°C), derating linearly at 0.28 mA/°C. This is the key parameter for DC or high-duty-cycle operation. The derating factor is crucial: as the ambient temperature (Ta) increases, the maximum safe continuous current decreases. For example, at 85°C, the max current would be approximately: 25 mA - [0.28 mA/°C * (85°C - 25°C)] = 25 mA - 16.8 mA = 8.2 mA.
• Operating & Storage Temperature Range: -35°C to +105°C. The device can be functionally operated and stored within this full range, though electrical performance will vary with temperature.
• Solder Conditions: Reflow soldering should be performed with the solder point 1/16 inch (approx. 1.6mm) below the seating plane, for a maximum of 3 seconds at 260°C. This prevents excessive thermal stress on the plastic package and the internal wire bonds.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at a standard test condition of Ta=25°C. They define how the device will behave in a circuit.

• Average Luminous Intensity (I_V): 200-600 μcd (microcandelas) at I_F=1mA. This is the light output. The wide range (200-600) indicates a binning process; specific units will fall within this range. Designers must account for this variation if consistent brightness is critical.
• Peak Emission Wavelength (λ_p): 650 nm (typical). This is the wavelength at which the optical output power is greatest. It falls in the deep red region of the spectrum.
• Dominant Wavelength (λ_d): 639 nm (typical). This is the single wavelength perceived by the human eye that matches the color of the light. It is often closer to the visual perception than the peak wavelength.
• Spectral Line Half-Width (Δλ): 20 nm (typical). This measures the spread of the emitted wavelengths. A value of 20 nm indicates a relatively pure, monochromatic red color.
• Forward Voltage per Chip (V_F): 2.10 (Min), 2.60 (Typ) Volts at I_F=20mA. This is the voltage drop across the LED when conducting. It is crucial for designing the current-limiting circuitry. The driver must supply at least 2.6V to overcome this drop before current flows significantly.
• Reverse Current per Segment (I_R): 100 μA (Max) at V_R=5V. This is the small leakage current that flows when the LED is reverse-biased. The datasheet explicitly notes that this condition is for test purposes only and the device should not be continuously operated under reverse bias.
• Luminous Intensity Matching Ratio: 2:1 (Max). For segments within the same digit (similar light area), the brightness of the dimmest segment will be no less than half the brightness of the brightest segment. This ensures visual uniformity.
• Cross Talk: < 2.5%. This specifies the amount of unwanted light emission from a segment that is intended to be off, when an adjacent segment is driven. A low value is important for clear character definition.

3. Binning System Explanation

The datasheet indicates that the device is \"Categorized for Luminous Intensity.\" This implies a binning process, though specific bin codes are not provided in this document. In general, LED manufacturers test and sort (bin) products based on key parameters to ensure consistency. For a display like the LTS-3861JD, the primary binning criteria likely include:

• Luminous Intensity Binning: As the I_V range is 200-600 μcd, units are probably grouped into narrower intensity bins (e.g., 200-300, 300-400 μcd, etc.). Purchasing from the same bin ensures uniform brightness across a multi-digit display.
• Forward Voltage (V_F) Binning: While not explicitly mentioned, V_F can also be binned. Matching V_F helps in designing simpler, more uniform current-drive circuits, especially when multiple segments/digits are driven in parallel.
• Wavelength/Color Binning: The dominant (639nm) and peak (650nm) wavelengths are given as typical. Tighter color bins may be available to ensure a consistent red hue across all units in an application.

Designers should consult the manufacturer for detailed binning information if application requirements demand high uniformity.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical/Optical Characteristics Curves\" which are essential for understanding device behavior under non-standard conditions. While the specific curves are not included in the provided text, their typical content and importance are analyzed below:

• Forward Current vs. Forward Voltage (I_F-V_F) Curve: This non-linear curve shows the relationship between applied voltage and resulting current. It demonstrates the exponential turn-on characteristic of an LED. The \"knee\" of this curve is around the typical V_F (2.6V). This curve is vital for designing constant-current drivers, as a small change in voltage can cause a large change in current and, consequently, brightness and power dissipation.
• Luminous Intensity vs. Forward Current (I_V-I_F) Curve: This shows how light output increases with drive current. It is generally linear over a wide range but will saturate at very high currents due to thermal and efficiency droop. This curve helps designers choose the operating current to achieve desired brightness while staying within power limits.
• Luminous Intensity vs. Ambient Temperature (I_V-T_a) Curve: LED light output decreases as junction temperature rises. This curve quantifies that derating. It is critical for applications operating in high-temperature environments, as the display may appear dimmer.
• Spectral Distribution Curve: A plot of relative intensity versus wavelength, showing the bell-shaped curve centered around 650nm with a half-width of 20nm. This defines the precise color characteristics of the \"Hyper Red\" emission.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Tolerances

The mechanical drawing specifies the physical size and pin layout. Key notes from the datasheet include:

• All dimensions are in millimeters, with general tolerances of ±0.25mm unless stated otherwise.
• Pin tip shift tolerance is ±0.40 mm, which is important for PCB hole placement.
• The recommended PCB hole diameter is 1.10 mm to accommodate the pins with sufficient clearance for soldering.
• Quality control criteria are specified for visual defects: foreign material on a segment (≤10 mils), bubbles in the segment (≤10 mils), bending of the reflector (≤1% of length), and surface ink contamination (≤20 mils).

5.2 Pin Connection and Polarity Identification

The device has a 10-pin single-row configuration. The internal circuit diagram and pinout table confirm it is a common anode type. This means the anodes (positive sides) of all LED segments are connected together internally and brought out to pins 1 and 6 (which are also connected together). Each segment cathode (negative side) has its own dedicated pin (A, B, C, D, E, F, G, DP). To illuminate a segment, the common anode pin(s) must be connected to a positive voltage supply (through a current-limiting resistor or driver), and the corresponding cathode pin must be pulled to a lower voltage (typically ground). The right-hand decimal point (DP) is on pin 7.

6. Soldering and Assembly Guidelines

Proper handling is essential for reliability. Based on the Absolute Maximum Ratings:

• Reflow Soldering: Follow the specified profile: maximum component body temperature should not exceed the rating, with solder time at peak temperature (260°C) limited to 3 seconds. The 1/16 inch seating plane rule helps prevent direct heat exposure to the plastic body.
• Hand Soldering: If necessary, use a temperature-controlled iron with a fine tip. Limit contact time to 3 seconds per pin. Avoid applying mechanical stress to the pins or package during soldering.
• Cleaning: Use cleaning agents compatible with the display's plastic material. Avoid ultrasonic cleaning unless explicitly approved, as it can damage the internal structure.
• Storage Conditions: Store in the specified temperature range (-35°C to +105°C) in a low-humidity, anti-static environment to prevent moisture absorption and electrostatic discharge damage.

7. Application Suggestions and Design Considerations

7.1 Typical Application Scenarios

The LTS-3861JD is well-suited for applications requiring a single, clear numeric readout with low power draw:

• Panel Meters and Instrumentation: Voltage, current, temperature, or frequency displays on test equipment, power supplies, or industrial controllers.
• Consumer Electronics: Display for clocks, timers, kitchen appliances, or audio equipment.
• Medical Devices: Simple readouts on portable or bedside monitors where low power and reliability are key.
• Automotive Aftermarket: Displays for auxiliary gauges (voltmeter, oil temperature).

7.2 Critical Design Considerations

• Current Limiting is Mandatory: LEDs are current-driven devices. A series current-limiting resistor must be used for each cathode pin (or a dedicated LED driver IC) to set the forward current (I_F). The resistor value is calculated as R = (V_supply - V_F) / I_F. Always use the maximum V_F (2.6V) from the datasheet for a conservative design to ensure current does not exceed the limit.
• Thermal Management: Adhere to the current derating curve with temperature. In high ambient temperature environments, reduce the drive current accordingly. Ensure adequate ventilation around the display on the PCB.
• Multiplexing for Multiple Digits: While this is a single-digit part, the common anode design is inherently suitable for multiplexing. In a multi-digit system, each digit's common anode is driven sequentially at a high frequency, while the segment cathodes are shared. This greatly reduces the number of required I/O pins on a microcontroller.
• Viewing Angle: Position the display considering its wide viewing angle to ensure readability for the end-user.

8. Technical Comparison and Differentiation

Compared to other seven-segment display technologies, the LTS-3861JD's use of AlInGaP Hyper Red chips offers distinct advantages:

• vs. Traditional GaAsP or GaP Red LEDs: AlInGaP technology typically offers higher luminous efficiency and brightness at the same drive current, along with better temperature stability and longer lifetime.
• vs. High-Efficiency Red (HER) LEDs: The term \"Hyper Red\" often denotes a specific, deeper red color point (around 639-650nm dominant wavelength) which can appear more vibrant and saturated compared to some standard red LEDs.
• vs. LCD Displays: Unlike LCDs, this LED display is emissive—it produces its own light. This makes it clearly visible in low-light or dark conditions without a backlight, and it offers a much wider viewing angle and faster response time.
• vs. Larger Digit Displays: The 0.3-inch size offers a good balance between readability and compactness, fitting where larger 0.5-inch or 0.8-inch digits would be too big.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive this display directly from a 5V microcontroller pin?
A: No. Connecting an LED directly to a logic pin is not recommended. The microcontroller pin cannot provide precise current limiting and may be damaged by the current sink/source demand. Always use a current-limiting resistor or a dedicated driver circuit. For a 5V supply and a target I_F of 10mA, the resistor would be R = (5V - 2.6V) / 0.01A = 240 Ohms.

Q2: Why are there two common anode pins (1 and 6)?
A: They are internally connected. Having two pins provides mechanical stability, better current distribution if multiple segments are on simultaneously, and layout flexibility on the PCB. You can connect one or both to your positive supply.

Q3: What does the \"Luminous Intensity Matching Ratio of 2:1\" mean for my design?
A: It means that within one physical unit, the dimmest segment could be half as bright as the brightest segment. If your design uses multiple LTS-3861JD digits, you should request parts from the same luminous intensity bin from your supplier to ensure brightness uniformity across digits, as the 2:1 ratio only applies internally.

Q4: The reverse current rating is 100µA at 5V. Is it okay to occasionally reverse-bias the display?
A: The datasheet states the reverse voltage condition is \"only for IR test\" and it \"cannot continue to operate at this situation.\" You must design your circuit to prevent reverse bias during normal operation, as sustained reverse voltage can degrade the LED.

10. Practical Design and Usage Case

Case: Designing a Single-Digit DC Voltmeter Readout (0-9V)
A designer is creating a simple voltmeter to display 0-9V in 1V steps using a microcontroller (MCU). The MCU has an ADC to read the voltage and GPIO pins to drive the display.

1. Circuit Design: The common anode pins (1 & 6) are connected to the MCU's positive supply rail (e.g., 3.3V or 5V) through a single current-limiting resistor? No. A better practice is to use a transistor (e.g., a PNP or a logic-level N-FET) switched by an MCU pin to control the common anode, allowing software to turn the entire digit on/off. Each segment cathode (pins 2,3,4,5,7,8,9,10) is connected to an MCU GPIO pin, each through its own individual current-limiting resistor. This allows per-segment brightness control and is safer than a single resistor on the common anode.
2. Resistor Calculation: For a 5V supply, target I_F=10mA, and using max V_F=2.6V: R = (5V - 2.6V) / 0.01A = 240 Ohms (use 220 or 270 Ohm standard value). Place one resistor on each of the 8 cathode lines.
3. Software: The MCU code converts the ADC reading to a digit (0-9). It uses a look-up table to map the digit to the pattern of segment cathodes (A-G) that need to be activated (driven low). It turns on the common anode transistor, then sets the cathode pins accordingly. For multiplexing multiple such digits, the code would cycle through each digit rapidly.
4. Thermal Check: At 10mA per segment and Ta=25°C, power per segment = 10mA * 2.6V = 26mW, well below the 70mW maximum. If all 7 segments of the digit '8' are on, total device dissipation is ~182mW, which is acceptable but requires verifying the PCB's local temperature rise.

11. Operating Principle Introduction

The LTS-3861JD operates on the fundamental principle of electroluminescence in a semiconductor p-n junction. The active region uses an AlInGaP heterostructure. When a forward voltage exceeding the junction's built-in potential (approximately 2.6V) is applied, electrons from the n-type region and holes from the p-type region are injected into the active region. There, they recombine radiatively—meaning the energy released from an electron falling into a hole is converted directly into a photon (light particle). The specific composition of the AlInGaP alloy determines the bandgap energy, which in turn dictates the wavelength (color) of the emitted photons, in this case, in the ~639-650 nm (red) range. Each segment of the digit is a separate LED chip or a set of chips wired in series/parallel, controlled by its own cathode pin.

12. Technology Trends and Developments

The field of LED displays continues to evolve. While the LTS-3861JD represents a mature and reliable technology, broader trends influencing this product category include:

• Increased Efficiency: Ongoing materials science research aims to improve the internal quantum efficiency (IQE) and light extraction efficiency of AlInGaP and other compound semiconductors, leading to displays that are brighter at lower currents or have longer battery life.
• Miniaturization: There is a constant drive for smaller pixel pitches and higher density, although for standard seven-segment displays, the 0.3-inch size remains a popular workhorse.
• Integration: Trends include integrating the LED driver circuitry (constant current sinks, multiplexing logic) directly into the display module or package, simplifying the external design for the end engineer.
• Color Gamut Expansion: While this is a monochrome red display, the underlying material science for red LEDs directly supports the development of full-color LED displays and micro-LED arrays, where red, green, and blue micro-LEDs are combined.
• Flexible and Novel Form Factors: Research into flexible substrates could eventually lead to bendable or curved seven-segment displays, though this is more relevant to newer OLED or micro-LED technologies than traditional packaged LEDs.

The LTS-3861JD, with its proven AlInGaP technology and clear specifications, remains a robust and effective solution for applications where a simple, reliable, low-power numeric display is required.