LTS-3361JF LED Display Datasheet - 0.3-inch (7.62mm) Digit Height - Yellow Orange Color - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Documentation

1. Product Overview

The LTS-3361JF is a single-digit, 7-segment plus decimal point LED display module. Its primary function is to provide a clear, bright numeric and limited alphanumeric readout in electronic devices. The core technology is based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material, which is specifically engineered to emit light in the yellow-orange spectrum. This material system is known for its high efficiency and good visibility. The display features a gray faceplate with white segment markings, offering a high-contrast appearance when the segments are illuminated. It is categorized by luminous intensity, allowing for selection based on brightness requirements.

1.1 Core Advantages and Target Market

The device offers several key advantages that make it suitable for a variety of applications. It features a 0.3-inch (7.62 mm) digit height, which provides a good balance between readability and compact size. The segments are designed to be continuous and uniform, ensuring a consistent and professional visual appearance. It operates with low power requirements, contributing to energy efficiency in the end product. The display delivers high brightness and high contrast, coupled with a wide viewing angle, making it easily readable from different perspectives. Its solid-state construction ensures high reliability and long operational life. These characteristics make the LTS-3361JF ideal for consumer electronics, industrial instrumentation, test and measurement equipment, automotive dashboards (secondary displays), and any application requiring a reliable, bright numeric indicator.

2. Technical Parameter Deep-Dive

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

2.1 Photometric and Optical Characteristics

The primary optical parameters are defined at an ambient temperature (Ta) of 25°C. The Average Luminous Intensity (Iv) is specified with a minimum of 200 µcd, a typical value, and a maximum of 600 µcd when driven at a forward current (IF) of 1 mA. This parameter, measured using a filter approximating the CIE photopic eye-response curve, indicates the perceived brightness. The Peak Emission Wavelength (λp) is 611 nm, while the Dominant Wavelength (λd) is 605 nm at IF=20mA. The slight difference between peak and dominant wavelength is typical and relates to the shape of the emission spectrum. The Spectral Line Half-Width (Δλ) is 17 nm, indicating the color purity; a narrower width would indicate a more monochromatic light. The Luminous Intensity Matching Ratio is specified as 2:1 maximum, meaning the brightness difference between the dimmest and brightest segment in a device should not exceed this ratio, ensuring uniformity.

2.2 Electrical Parameters

The key electrical parameter is the Forward Voltage per Segment (VF), which has a typical value of 2.6V at IF=20mA, with a minimum of 2.05V. This value is crucial for designing the current-limiting circuitry. The Reverse Current per Segment (IR) is a maximum of 100 µA at a Reverse Voltage (VR) of 5V, indicating the leakage current in the off-state. The Continuous Forward Current per Segment is rated at 25 mA at 25°C, with a derating factor of 0.33 mA/°C. This means the maximum allowable continuous current decreases as ambient temperature rises above 25°C to prevent overheating. A Peak Forward Current of 90 mA is allowed under pulsed conditions (1/10 duty cycle, 0.1ms pulse width), which can be used for multiplexing or achieving higher instantaneous brightness.

2.3 Absolute Maximum Ratings and Thermal Considerations

These ratings define the limits beyond which permanent damage may occur. The Power Dissipation per Segment is 70 mW. Exceeding this, especially combined with high ambient temperature, can lead to accelerated degradation or failure. The Operating and Storage Temperature Range is from -35°C to +85°C, defining the environmental conditions for reliable operation and non-operational storage. The Solder Temperature specification is critical for assembly: the device can withstand a maximum of 260°C for up to 3 seconds, measured 1.6mm (1/16 inch) below the seating plane of the package. This guides reflow soldering profile settings.

3. Binning System Explanation

The datasheet explicitly states that the device is categorized for luminous intensity. This refers to a binning or sorting process post-manufacturing. Due to inherent variations in the semiconductor epitaxial growth and chip processing, LEDs from the same production batch can have slightly different brightness outputs. Manufacturers measure the luminous intensity of each unit and sort them into different "bins" or categories based on predefined intensity ranges (e.g., 200-300 µcd, 300-400 µcd, etc.). This allows customers to select parts that meet specific brightness consistency requirements for their application, ensuring uniform appearance across multiple displays in a product. The datasheet provides the overall min/typ/max range (200-600 µcd), but ordered parts would typically fall within a tighter sub-range.

4. Performance Curve Analysis

While the specific curves are not detailed in the provided text, typical curves for such a device would include:

• Forward Current vs. Forward Voltage (I-V Curve): This non-linear curve shows the relationship between the current flowing through the LED and the voltage across it. The "knee" of this curve is around the typical forward voltage (2.6V). Designers use this to determine the necessary supply voltage and series resistor value for proper current regulation.
• Luminous Intensity vs. Forward Current (I-L Curve): This curve shows how light output increases with current. It is generally linear over a range but will saturate at very high currents due to thermal and efficiency droop.
• Luminous Intensity vs. Ambient Temperature: This curve demonstrates the thermal quenching effect. As the junction temperature of the LED increases, its light output typically decreases. The derating factor for continuous current (0.33 mA/°C) is directly related to managing this effect.
• Spectral Distribution: A graph showing the relative intensity of light emitted across different wavelengths, centered around 611 nm (peak) with a 17 nm half-width.

5. Mechanical and Package Information

The device is provided in a standard LED display package. The digit height is 0.3 inches (7.62 mm). The package includes a gray face and white segments for optimal contrast when unlit and lit. A detailed dimensioned drawing is referenced in the datasheet (PAGE 2 of 5), with all dimensions provided in millimeters and standard tolerances of ±0.25 mm unless otherwise noted. This drawing is essential for PCB footprint design and ensuring proper fit within the product enclosure.

5.1 Pinout and Polarity Identification

The LTS-3361JF is a common cathode device. This means all the cathodes (negative terminals) of the individual LED segments are connected together internally. The pin connection table is as follows: Pin 1 and Pin 6 are both common cathode connections. The anodes (positive terminals) for segments A, B, C, D, E, F, G, and the decimal point (DP) are connected to pins 10, 9, 8, 5, 4, 2, 3, and 7 respectively. Using a common cathode configuration simplifies multiplexing when driving multiple digits, as the cathodes can be switched to ground sequentially.

6. Soldering and Assembly Guidelines

The key guideline provided is for soldering temperature: the component body must not be exposed to temperatures exceeding 260°C for more than 3 seconds during the reflow process, as measured at a point 1.6mm below the package seating plane. This is a standard rating for lead-free soldering processes. Designers must ensure their reflow oven profile complies with this limit to prevent damage to the internal wire bonds or the epoxy package. Standard ESD (Electrostatic Discharge) precautions should be observed during handling. For storage, the specified range is -35°C to +85°C in a dry environment.

7. Application Suggestions

7.1 Typical Application Circuits

The most common drive method is using a series current-limiting resistor for each segment anode. The resistor value (R) is calculated using the formula: R = (Vcc - Vf) / If, where Vcc is the supply voltage, Vf is the forward voltage of the LED segment (use 2.6V typical), and If is the desired forward current (e.g., 10-20 mA for good brightness). For example, with a 5V supply and a target current of 15 mA: R = (5 - 2.6) / 0.015 = 160 Ohms. A 150 or 180 Ohm resistor would be suitable. For multi-digit applications, a multiplexing technique is employed. A microcontroller sequentially activates the common cathode of each digit while outputting the segment pattern for that digit on the common anode lines. This reduces the number of required I/O pins significantly.

7.2 Design Considerations

• Current Management: Do not exceed the absolute maximum continuous current (25 mA at 25°C). Use the derating factor in high-temperature environments. For multiplexed designs, ensure the peak pulse current (90 mA max) is not exceeded when calculating the instantaneous current during the short ON time.
• Heat Dissipation: While power dissipation is low per segment, in a multiplexed design with multiple segments on simultaneously or in high ambient temperatures, consider the total power and ensure adequate ventilation.
• Viewing Angle: The wide viewing angle is beneficial, but for optimal readability, the display should be oriented perpendicular to the primary user sightline.
• Brightness Consistency: If uniform brightness across multiple units is critical, specify parts from the same luminous intensity bin from the manufacturer.

8. Technical Comparison and Differentiation

The primary differentiator of the LTS-3361JF is its use of AlInGaP (Aluminium Indium Gallium Phosphide) technology for yellow-orange emission. Compared to older technologies like GaAsP (Gallium Arsenide Phosphide), AlInGaP offers significantly higher luminous efficiency, resulting in brighter output at the same current, or the same brightness at lower power. It also generally provides better temperature stability and longer lifetime. Compared to displays using wavelength-converting phosphors (like some white LEDs), AlInGaP provides a purer, more saturated color directly from the semiconductor junction. The common cathode configuration is standard but offers an advantage in simplicity for microcontroller-based multiplexing compared to common anode in some system architectures.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of having two common cathode pins (Pin 1 and Pin 6)?
A: This is primarily for mechanical and layout symmetry on the PCB. Electrically, they are connected internally. Using both pins helps with current distribution if many segments are lit simultaneously and provides better mechanical stability when soldered.

Q: Can I drive this display directly from a 3.3V microcontroller pin?
A: Possibly, but with limitations. The typical Vf is 2.6V, leaving only 0.7V for the current-limiting resistor at 3.3V. This requires a very small resistor value (e.g., ~47 Ohms for 15mA), which may draw more current than the MCU pin can source (often 20-25mA max per pin). It's safer to use a transistor or driver IC.

Q: What does "Luminous Intensity Matching Ratio 2:1" mean in practice?
A: It means that within a single display unit, the dimmest segment will be no less than half as bright as the brightest segment. This ensures visual uniformity when all segments are lit.

Q: How do I interpret the Peak Forward Current rating for multiplexing?
A: If you multiplex 4 digits with a 1/4 duty cycle, you might drive each digit with 4x the desired average current for 1/4 of the time. If you want an average brightness corresponding to 10mA, you could pulse at 40mA. This is within the 90mA peak rating, but you must ensure the pulse width (ON time per cycle) is 0.1ms or less as per the rating condition, or calculate the resulting junction temperature.

10. Design and Usage Case Example

Case: Designing a Simple 4-Digit Voltmeter Readout.
A designer is creating a benchtop power supply unit that requires a 4-digit voltage display (0.000 to 19.99V). They select four LTS-3361JF displays. To minimize microcontroller I/O pins, they use a multiplexing scheme. The four common cathode pins (two per digit) are connected to four NPN transistors, controlled by four MCU pins. The eight segment anode lines (A-G, DP) are connected to eight MCU pins via 180-ohm current-limiting resistors (for a 5V system). The MCU runs a timer interrupt every 5ms. In each interrupt, it turns off the previous digit's transistor, calculates the segment pattern for the next digit based on the measured voltage, outputs that pattern to the anode pins, and then turns on the transistor for that digit. This cycles continuously, creating a stable, flicker-free display. The yellow-orange color is chosen for good visibility under various lighting conditions. The designer ensures the total ON time per digit and instantaneous current per segment stay within the absolute maximum ratings.

11. Technology Principle Introduction

The LTS-3361JF is based on Light Emitting Diode (LED) technology. An LED is a semiconductor p-n junction diode. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected into the junction region. When these charge carriers recombine, they release energy. In a standard silicon diode, this energy is released primarily as heat. In a direct bandgap semiconductor like AlInGaP, a significant portion of this energy is released as photons (light). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material. AlInGaP alloys allow engineers to "tune" the bandgap to produce light in the red, orange, amber, and yellow-green parts of the spectrum. The device uses a non-transparent GaAs substrate, which absorbs some of the emitted light, but the design and material efficiency still yield high brightness. Each segment of the display is a separate LED chip or a set of chips, wired internally to the corresponding pins.

12. Technology Trends

While AlInGaP remains a high-performance technology for red-to-yellow colors, the broader LED display market shows several trends. There is a continuous drive towards higher efficiency (more lumens per watt), reducing power consumption in battery-operated devices. Miniaturization is another trend, with smaller digit heights and pixel pitches becoming available for denser information display. The development of direct-view microLEDs promises even higher brightness, contrast, and reliability for future ultra-high-resolution displays, though this technology is currently focused on smaller pixels than 7-segment digits. For alphanumeric displays, there is also a trend towards integration, with driver ICs, microcontrollers, and sometimes even sensors being combined with the display module into a single, smart component to simplify end-product design. However, for standard, cost-effective, single-digit numeric indicators like the LTS-3361JF, the established AlInGaP technology offers an excellent balance of performance, reliability, and cost.