LTS-360KR LED Display Datasheet - 0.36-inch Digit Height - Super Red Color - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTS-360KR is a single-digit, seven-segment alphanumeric display designed for applications requiring clear, bright numeric readouts. Its primary function is to provide a highly legible visual output for digital instruments, consumer electronics, industrial control panels, and test equipment. The device utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) LED technology grown on a GaAs substrate, which is renowned for producing high-efficiency red light emission. This specific material system allows the display to achieve superior brightness and color purity compared to older LED technologies.

The core advantages of this display module include its excellent character appearance, which is achieved through continuous uniform segments that form smooth, well-defined numerals. It offers high brightness and high contrast against its gray face, ensuring readability even in brightly lit environments. A wide viewing angle is another significant benefit, allowing the display to be read clearly from various positions. Furthermore, the device is categorized for luminous intensity, meaning units are binned and tested to meet specific brightness criteria, providing consistency in production batches. The package is also lead-free, complying with RoHS (Restriction of Hazardous Substances) directives, making it suitable for modern electronic manufacturing.

2. In-Depth Technical Parameter Analysis

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's functionality. The key parameters are measured under standard test conditions at an ambient temperature (Ta) of 25°C.

• Average Luminous Intensity (Iv): This parameter defines the perceived brightness of the lit segments. The typical value is 975 µcd (microcandelas) when driven at a forward current (IF) of 1mA. The minimum specified value is 320 µcd. This high intensity ensures the display is easily visible.
• Peak Emission Wavelength (λp): The wavelength at which the LED emits the maximum optical power. For the LTS-360KR, this is typically 639 nanometers (nm) at IF=20mA, placing it firmly in the red region of the visible spectrum.
• Dominant Wavelength (λd): This is 631 nm at IF=20mA. It represents the single wavelength that best matches the perceived color of the LED to the human eye, which is a vibrant super red.
• Spectral Line Half-Width (Δλ): This is approximately 20 nm, indicating the spectral purity or the narrowness of the emitted light band. A smaller value indicates a more monochromatic light source.
• Luminous Intensity Matching Ratio (Iv-m): This ratio, specified as 2:1 maximum, ensures uniformity across the different segments of the digit. It means the brightest segment will not be more than twice as bright as the dimmest segment when driven under the same conditions, providing a consistent appearance.

All luminous intensity measurements are performed using a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring the data correlates with human visual perception.

2.2 Electrical and Absolute Maximum Ratings

Adherence to these ratings is critical for reliable operation and preventing permanent damage to the device.

• Continuous Forward Current per Segment: The maximum recommended continuous DC current for each individual LED segment is 25 mA. Exceeding this can lead to accelerated degradation or failure.
• Peak Forward Current per Segment: For pulsed operation, a higher current is permissible. The device can handle a peak current of 90 mA per segment under specific conditions: a frequency of 1 kHz and a duty cycle of 10%.
• Power Dissipation per Segment: The maximum power that can be dissipated by a single segment is 70 mW. This is calculated as Forward Voltage (VF) multiplied by Forward Current (IF).
• Forward Current Derating: The maximum continuous forward current must be reduced above 25°C. The derating factor is 0.33 mA per degree Celsius. For example, at 85°C, the maximum allowable continuous current would be approximately 25 mA - ((85-25) * 0.33 mA) ≈ 5.2 mA.
• Forward Voltage per Segment (VF): Typically 2.6V with a maximum of 2.6V when IF=10mA. The minimum is 2.1V. This parameter is crucial for designing the current-limiting circuitry.
• Reverse Voltage (VR): The maximum reverse voltage that can be applied across a segment is 5V. Exceeding this can cause breakdown and damage the LED.
• Reverse Current (IR): The leakage current when the maximum reverse voltage of 5V is applied is typically 100 µA or less.

2.3 Thermal and Environmental Specifications

• Operating Temperature Range: The display is designed to function reliably in ambient temperatures from -35°C to +85°C.
• Storage Temperature Range: The device can be stored without operation in temperatures from -35°C to +85°C.
• Solder Temperature: During assembly, the device can withstand a soldering temperature of 260°C for 5 seconds, measured 1/16 inch (approximately 1.6 mm) below the seating plane of the package. This is a standard requirement for wave or reflow soldering processes.

3. Binning and Categorization System

The datasheet explicitly states that the device is categorized for luminous intensity. This is a critical quality control and design aspect. In LED manufacturing, there are natural variations in output even within the same production batch. Binning is the process of sorting LEDs based on specific measured parameters after production. For the LTS-360KR, the primary binning criterion is its luminous intensity (Iv). By purchasing binned parts, designers ensure that all displays in their product have a consistent brightness level, avoiding noticeable variations between units. While the datasheet provides the min/typ/max range (320-975 µcd), manufacturers typically offer these parts in tighter, predefined intensity bins (e.g., 800-900 µcd, 900-1000 µcd). Designers should consult with suppliers for available bin codes to specify the required brightness consistency for their application.

4. Performance Curve Analysis

While the specific graphs are not detailed in the provided text, typical performance curves for such a device would include the following, all crucial for robust circuit design:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph shows how the light output increases with increasing forward current. It is typically non-linear, with efficiency often dropping at very high currents due to thermal effects.
• Forward Voltage vs. Forward Current (V-I Curve): This shows the exponential relationship typical of diodes. It is essential for determining the necessary drive voltage and for designing constant-current drivers.
• Relative Luminous Intensity vs. Ambient Temperature: This curve demonstrates the thermal derating of light output. As temperature increases, the luminous intensity generally decreases. Understanding this helps design for consistent brightness over the intended operating temperature range.
• Spectral Distribution: A plot showing the relative power emitted across different wavelengths, centered around the peak wavelength of 639 nm, with a characteristic width defined by the 20 nm half-width.

5. Mechanical and Package Information

The LTS-360KR is a through-hole (DIP) package with a 0.36-inch (9.14 mm) digit height. The package dimensions are provided in the datasheet with a standard tolerance of ±0.25 mm unless otherwise noted. A key mechanical note is the pin tip's shift tolerance of ±0.4 mm, which is important for PCB layout and automated insertion processes. The display features a gray face with white segments, which provides the high contrast mentioned in the features. The internal circuit diagram confirms it is a common anode configuration. This means the anodes of all LED segments are connected together internally and brought out to two pins (Pin 1 and Pin 6, which are internally connected). Each segment cathode (A, B, C, D, E, F, G, and the Decimal Point) has its own dedicated pin. This configuration is common and requires the driving circuit to sink current through the individual cathode pins while providing a positive voltage to the common anode.

6. Soldering and Assembly Guidelines

The absolute maximum ratings provide the key guideline for soldering: the device can withstand a temperature of 260°C for 5 seconds at a point 1.6 mm below the seating plane. This aligns with standard lead-free reflow or wave soldering profiles. Designers should ensure their assembly process does not exceed this thermal budget. Standard ESD (Electrostatic Discharge) precautions should be observed during handling. For storage, the specified range of -35°C to +85°C should be maintained in a dry environment to prevent moisture absorption, which could cause popcorning during reflow.

7. Application Suggestions and Design Considerations

7.1 Typical Application Scenarios

The LTS-360KR is ideal for any device requiring a clear, single-digit numeric display. Common applications include:

• Digital multimeters, oscilloscopes, and other test and measurement equipment.
• Industrial control panels and process indicators.
• Consumer appliances like microwave ovens, washing machines, and audio equipment.
• Automotive aftermarket gauges and displays (considering the wide temperature range).
• Clock and timer modules.

7.2 Critical Design Considerations

• Current Limiting: LEDs are current-driven devices. A series current-limiting resistor is mandatory for each segment (or an integrated constant-current driver) to prevent exceeding the maximum continuous forward current (25 mA). The resistor value is calculated using the formula: R = (Vcc - VF) / IF, where Vcc is the supply voltage, VF is the forward voltage of the LED (use 2.6V for design margin), and IF is the desired operating current (e.g., 10-20 mA for good brightness).
• Drive Circuitry: For a common anode display, the microcontroller or driver IC must be configured to sink current. This typically involves setting the common anode pin to a logic high (Vcc) and pulling the desired segment cathode pins to logic low (ground) to turn them on.
• Multiplexing: For multi-digit displays, multiplexing is a common technique to control many segments with fewer I/O pins. While the LTS-360KR is a single digit, understanding this is key for system design. Multiplexing involves rapidly switching which digit is active. The peak current rating (90 mA at 10% duty cycle) becomes relevant here if using pulsed currents higher than 25 mA to achieve higher perceived brightness during the short on-time.
• Thermal Management: Although power dissipation is low per segment, ensuring adequate ventilation and avoiding placement near other heat-generating components will help maintain LED efficiency and longevity, especially when operating at high ambient temperatures.
• Viewing Angle: The wide viewing angle is beneficial, but the PCB layout and product enclosure should be designed to avoid mechanical obstructions that might limit this angle for the end-user.

8. Technical Comparison and Differentiation

The primary differentiator of the LTS-360KR is its use of AlInGaP LED technology. Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) red LEDs, AlInGaP offers significantly higher luminous efficiency. This means it can produce the same brightness at a lower current, improving power efficiency, or much higher brightness at the same current. It also provides better color saturation and stability over temperature and lifetime. The gray face/white segment design offers superior contrast compared to displays with diffused or tinted faces. The categorization (binning) for luminous intensity is a key feature for professional applications where display uniformity is critical, setting it apart from non-binned, lower-cost alternatives where brightness may vary noticeably from unit to unit.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: What is the purpose of having two common anode pins (Pin 1 and Pin 6)?
A1: They are internally connected. This dual-pin design provides mechanical stability during PCB insertion and offers two connection points for the common anode on the PCB, which can be helpful for routing the higher current that may be needed when multiple segments are lit simultaneously.

Q2: Can I drive this display directly from a 5V microcontroller pin?
A2: No. You must use a current-limiting resistor in series with each segment. For a 5V supply and a target current of 10mA, using a typical VF of 2.6V, the resistor value would be (5V - 2.6V) / 0.01A = 240 Ohms. Always verify the actual current does not exceed the maximum rating.

Q3: What does \"categorized for luminous intensity\" mean for my design?
A3: It means you can specify and purchase these displays within a specific, narrow range of brightness (e.g., a specific bin code). This ensures all displays in your production run will have nearly identical brightness, preventing one unit from looking dimmer or brighter than another, which is crucial for product quality.

Q4: How do I interpret the forward current derating specification?
A4: The maximum continuous current of 25 mA is only guaranteed at 25°C. For every degree Celsius above 25°C, you must reduce the maximum current by 0.33 mA. If your device operates at 60°C, the derating is (60-25)*0.33 = 11.55 mA. Therefore, the maximum safe continuous current at 60°C is 25 mA - 11.55 mA = 13.45 mA per segment.

10. Practical Design and Usage Case

Case: Designing a Single-Digit Voltmeter Readout. A designer is creating a simple panel meter to display 0-9. They select the LTS-360KR for its clarity and wide viewing angle. The system uses a microcontroller with 5V logic. The designer connects the common anode pins (1 & 6) to the 5V rail through a single current-limiting resistor sized for the total possible current (e.g., when digit \"8\" is displayed, all 7 segments are on). Alternatively, they connect it directly to 5V and place individual current-limiting resistors on each of the 8 cathode pins (segments A-G and DP), each calculated for a 10-15 mA segment current. The microcontroller I/O pins, configured as open-drain or simply set to logic low, sink the current to ground to illuminate the segments. The designer specifies LTS-360KR parts from a bin with a minimum intensity of 800 µcd to ensure adequate brightness in the final product's enclosure. They ensure the PCB layout keeps the display away from a nearby voltage regulator to avoid localized heating that could reduce brightness.

11. Operational Principle Introduction

A seven-segment display is an assembly of light-emitting diodes (LEDs) arranged in a figure-eight pattern. By selectively illuminating specific segments (labeled A through G), it can form all ten Arabic numerals (0-9) and some letters. The LTS-360KR uses AlInGaP semiconductor material. When a forward voltage exceeding the diode's threshold (about 2.1V) is applied, electrons and holes recombine in the active region of the semiconductor, releasing energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light—in this case, super red at ~639 nm. The common anode configuration simplifies driving circuitry when using microcontroller ports that are better at sinking current than sourcing it.

12. Technology Trends and Context

While seven-segment displays remain ubiquitous for numeric readouts, the underlying LED technology continues to evolve. AlInGaP represents a mature, high-performance technology for red, orange, and yellow LEDs. Current trends in display technology include a shift towards surface-mount device (SMD) packages for automated assembly, higher density multi-digit modules, and the integration of drivers and controllers within the display package. There is also ongoing development in materials like GaN (Gallium Nitride) for blue and green, and the use of phosphors to create white light. However, for dedicated, high-reliability, high-visibility single-digit indicators, through-hole AlInGaP displays like the LTS-360KR continue to be a robust and optimal choice due to their proven reliability, excellent optical characteristics, and ease of use in prototyping and certain industrial applications.