LTS-3861JF LED Display Datasheet - 0.3-inch (7.62mm) Digit Height - AlInGaP Yellow Orange - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTS-3861JF is a single-digit, 7-segment plus right-hand decimal point LED display module. Its primary function is to provide a clear, highly visible numeric and limited alphanumeric character output in electronic devices. The core technology utilizes Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material for the LED chips, which is known for producing high-efficiency light in the yellow-orange region of the spectrum. The device features a gray face with white segments, enhancing contrast and readability. It is designed as a common anode configuration, simplifying drive circuitry in many microcontroller-based applications.

1.1 Core Advantages and Target Market

The key advantages of this display stem from its AlInGaP construction and design. It offers high brightness and excellent contrast, making it suitable for applications where visibility under various lighting conditions is critical. The wide viewing angle ensures the display remains legible from off-axis positions. Its low power requirement and solid-state reliability make it ideal for long-term use in consumer and industrial electronics. The primary target markets include instrumentation panels, point-of-sale equipment, household appliances, industrial control units, and communication devices where a simple, reliable numeric readout is needed.

2. In-Depth Technical Parameter Analysis

This section provides a detailed, objective interpretation of the electrical and optical characteristics specified in the datasheet.

2.1 Photometric and Optical Characteristics

The luminous intensity is categorized, with a typical value of 600 microcandelas (ucd) at a forward current of 1mA. This parameter is measured using a sensor filtered to match the CIE photopic eye-response curve, ensuring the value correlates with human perception of brightness. The dominant wavelength is 605 nanometers (nm), placing the output firmly in the yellow-orange color range. The spectral line half-width is 17 nm, indicating a relatively pure, saturated color with minimal spectral spread. The luminous intensity matching ratio between segments is specified at 2:1, ensuring uniform appearance across the digit.

2.2 Electrical Parameters

The forward voltage per LED chip is 2.60 Volts typical at 20mA. Designers must account for the forward voltage range (2.05V to 2.60V) when designing the current-limiting circuitry to ensure consistent brightness across production batches. The reverse current is specified at a maximum of 100 microamperes at 5V reverse bias. It is critically important to note that this reverse voltage condition is for test purposes only; the device is not designed for continuous operation under reverse bias. The absolute maximum ratings define the operational limits: 70mW power dissipation per segment, a peak forward current of 90mA under pulsed conditions (1/10 duty, 0.1ms pulse), and a continuous forward current of 25mA at 25°C, derating linearly by 0.33 mA/°C above that temperature.

2.3 Thermal and Environmental Ratings

The device is rated for an operating temperature range of -35°C to +85°C, with an identical storage temperature range. This wide range supports deployment in environments subject to significant temperature variations. The solder temperature rating is crucial for assembly: the component body temperature must not exceed its maximum rating during soldering, with a guideline of 260°C for 5 seconds for the leads 1/16 inch (approximately 1.6mm) below the seating plane.

3. Binning and Categorization System

The datasheet indicates that the devices are categorized for luminous intensity. This means units are tested and sorted into different bins based on their measured light output at a standard test current (typically 1mA or 20mA). This allows designers to select parts with consistent brightness for a given application. While specific bin codes are not detailed in this excerpt, the 2:1 intensity matching ratio specification ensures that segments within a single device will have reasonably uniform brightness. Designers should consult the manufacturer for detailed binning information if tight brightness uniformity across multiple displays is required.

4. Performance Curve Analysis

Typical performance curves are referenced in the datasheet. These graphs are essential for understanding device behavior beyond the single-point specifications at 25°C. They typically include:

• IV Curve (Current vs. Voltage): Shows the relationship between forward voltage and forward current. This curve is non-linear and crucial for designing the correct current-limiting resistor or constant-current driver.
• Luminous Intensity vs. Forward Current: Illustrates how light output increases with current. It helps determine the optimal drive current for a desired brightness level while considering power dissipation and lifetime.
• Luminous Intensity vs. Ambient Temperature: Demonstrates how light output decreases as the junction temperature rises. This is critical for applications operating at high ambient temperatures or high drive currents.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at 611nm and the spectral width.

These curves allow engineers to predict performance under real-world, non-ideal conditions.

5. Mechanical and Package Information

The display has a digit height of 0.3 inches (7.62 mm). The package dimensions drawing provides critical mechanical data for PCB footprint design and enclosure fitting. Key tolerances are noted: ±0.25mm for most dimensions and a pin tip shift tolerance of ±0.4 mm. The recommended PCB hole diameter for the pins is 1.40 mm. The datasheet also includes quality control notes regarding acceptable levels of foreign material, bubbles in the segment, bending of the reflector, and surface ink contamination.

5.1 Pinout and Circuit Diagram

The device has a 10-pin single-row configuration. The internal circuit diagram shows a common anode design, where the anodes of all LEDs for a given digit are connected together. The pin connection table is essential for correct wiring:
Pin 1: Common Anode
Pin 2: Cathode F (segment)
Pin 3: Cathode G (segment)
Pin 4: Cathode E (segment)
Pin 5: Cathode D (segment)
Pin 6: Common Anode (connected internally to Pin 1)
Pin 7: Cathode D.P. (Decimal Point)
Pin 8: Cathode C (segment)
Pin 9: Cathode B (segment)
Pin 10: Cathode A (segment)
The dual anode pins (1 and 6) help in current distribution and can be tied together on the PCB.

6. Soldering and Assembly Guidelines

6.1 Reflow and Manual Soldering

For automated soldering processes, the condition is specified as 260°C for 5 seconds, measured 1.6mm below the seating plane. For manual soldering, a higher iron temperature of 350°C ±30°C is allowed, but the contact time must be limited to within 5 seconds. Exceeding these time-temperature profiles can damage the internal epoxy, LED chips, or wire bonds.

6.2 Storage and Handling

While not explicitly detailed in the excerpt, standard ESD (Electrostatic Discharge) precautions apply to LED devices. They should be stored in anti-static packaging in a controlled environment within the specified storage temperature range (-35°C to +85°C) to prevent moisture absorption and other degradation.

7. Application Notes and Design Considerations

7.1 Typical Application Circuits

Being a common anode display, the anodes are typically connected to a positive supply voltage (Vcc) through a current-limiting resistor or, preferably, driven by a constant-current source or a microcontroller pin configured as a current source (if within its capabilities). The cathode pins are connected to ground (sink current) to turn on a segment. This is the opposite of a common cathode display. Multiplexing several digits is a common technique to save I/O pins, where anodes are switched rapidly while the corresponding cathode patterns are presented.

7.2 Critical Design Warnings

The \"Cautions\" section highlights several vital points:
1. Current Limiting is Mandatory: LEDs are current-driven devices. A series resistor or active constant-current circuit is always required to prevent thermal runaway and destruction.
2. Consider Forward Voltage Variation: The circuit must be designed to provide the intended drive current over the full VF range (2.05V-2.60V).
3. Avoid Reverse Bias: The driving circuit should incorporate protection (like a diode in parallel) to prevent reverse voltage spikes during power cycling.
4. Thermal Management: The drive current must be derated for high ambient temperatures. Excess current or high operating temperature leads to accelerated light output degradation and premature failure.
5. Application Scope: The device is intended for standard electronic equipment. For safety-critical applications (aviation, medical, etc.), specific consultation and qualification are necessary.

8. Reliability and Testing

The device undergoes a comprehensive suite of reliability tests based on military (MIL-STD), Japanese (JIS), and internal standards. These include:
- Operating Life Test (RTOL): 1000 hours at maximum rated current.
- Environmental Stress Tests: High Temperature/Humidity Storage, High/Low Temperature Storage, Temperature Cycling, and Thermal Shock.
- Process Robustness Tests: Solder Resistance and Solderability tests.
These tests validate the device's ability to withstand the rigors of manufacturing, storage, and long-term operation.

9. Comparison and Differentiation

The LTS-3861JF's primary differentiation lies in its use of AlInGaP technology for yellow-orange emission. Compared to older technologies like GaAsP, AlInGaP offers significantly higher luminous efficiency and better temperature stability, resulting in brighter, more consistent output. The gray face/white segment design provides superior contrast compared to all-diffused packages. Its 0.3-inch digit size targets a specific niche between smaller, less readable displays and larger, higher-power ones.

10. Frequently Asked Questions (FAQ)

Q: What is the difference between common anode and common cathode?
A: In a common anode display, all LED anodes are connected together to Vcc, and segments are turned ON by sinking current (bringing the cathode low). In common cathode, all cathodes are connected to ground, and segments are turned ON by sourcing current (driving the anode high). The driving circuit must match the type.

Q: How do I calculate the current-limiting resistor value?
A: Use Ohm's Law: R = (V_supply - VF_LED) / I_desired. Use the maximum VF from the datasheet (2.60V) to ensure sufficient current at the low end of the VF range. For a 5V supply and 20mA desired current: R = (5V - 2.6V) / 0.02A = 120 Ohms. Always check the resistor power rating: P = I^2 * R.

Q: Can I drive this display directly from a microcontroller pin?
A: It depends on the MCU's pin current sourcing/sinking capability. Many MCUs can sink more current than they can source. For a common anode display (sink current), you may be able to drive it directly if the segment current (e.g., 10-20mA) is within the MCU's sink current specification per pin and total package limit. A driver IC (e.g., 74HC595 shift register with TPIC6B595 sink driver, or a dedicated LED driver) is often used for multiplexing and providing higher current.

11. Practical Application Example

Scenario: Designing a simple digital timer display.
Four LTS-3861JF digits are used to show minutes and seconds (MM:SS). A microcontroller with limited I/O pins is chosen. Implementation: Use multiplexing. Connect all corresponding segment cathodes (A, B, C, D, E, F, G, DP) of the four digits together. These eight lines connect to eight microcontroller pins configured as outputs (to sink current). Each digit's common anode pin is connected to a separate microcontroller pin via a small NPN transistor (e.g., 2N3904) that can handle the total digit current (up to 8 segments * 20mA = 160mA). The microcontroller rapidly cycles through turning on one transistor (enabling one digit) while outputting the segment pattern for that digit on the cathode lines. A refresh rate of >100Hz prevents visible flicker. Current-limiting resistors are placed on either the cathode lines or the anode paths.

12. Technology Principle

AlInGaP (Aluminium Indium Gallium Phosphide) is a III-V compound semiconductor. When forward-biased, electrons and holes recombine in the active region, releasing energy in the form of photons. The specific ratio of Al, In, Ga, and P in the crystal lattice determines the bandgap energy, which directly defines the wavelength (color) of the emitted light. For yellow-orange light (~605nm), a specific composition is used. AlInGaP is grown on a GaAs substrate. It is known for high internal quantum efficiency and good performance at elevated temperatures compared to other material systems for red-yellow colors.

13. Industry Trends

The trend in discrete LED displays is towards higher efficiency, wider color gamuts, and integration with surface-mount technology (SMT). While AlInGaP remains dominant for high-performance amber and red, AllnGaN-based devices are pushing further into the green and yellow spectrum. There is also a general industry shift towards finer-pitch, direct-view LED modules for large displays, reducing the demand for discrete segmented digits in some applications. However, for simple, low-cost, highly reliable numeric readouts in industrial and consumer devices, segmented LED displays like the LTS-3861JF remain a robust and practical solution due to their simplicity, durability, and ease of interface.