LTS-313AJD LED Display Datasheet - 0.3-inch Digit Height - Hyper Red Color - 2.6V Forward Voltage - English Technical Document

1. Product Overview

This document details the specifications for a compact, single-digit, seven-segment alphanumeric display module. The device is engineered for applications requiring clear, bright numeric indication with minimal power consumption. Its core design philosophy centers on providing excellent readability and reliability in a small form factor.

The display utilizes advanced semiconductor materials to achieve its characteristic output. It is categorized for consistent luminous intensity, ensuring uniformity in batch production and predictable performance in end-user applications.

1.1 Core Advantages and Target Market

The primary advantages of this display include its very low current requirement, which makes it suitable for battery-powered or energy-sensitive circuits. The high brightness and contrast ratio, combined with a wide viewing angle, ensure legibility under various lighting conditions and from different perspectives. The solid-state construction offers inherent reliability and long operational life compared to mechanical or filament-based displays.

Its 0.3-inch digit height positions it ideally for portable instruments, consumer electronics, panel meters, industrial control interfaces, and any embedded system where space is at a premium but clear numeric feedback is essential. The continuous, uniform segment design contributes to an excellent character appearance, enhancing user experience.

2. Technical Specifications Deep Dive

This section provides an objective and detailed analysis of the electrical, optical, and physical parameters defined in the datasheet.

2.1 Photometric and Optical Characteristics

The light-emitting elements are based on Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor technology, specifically in a Hyper Red color formulation. This material system is known for high efficiency and good temperature stability in the red-orange wavelength region.

• Average Luminous Intensity (I_V): Ranges from 200 to 600 microcandelas (μcd) at a standard test current of 1mA. This parameter defines the perceived brightness. The categorization mentioned implies devices are binned or sorted based on measured intensity to fall within this guaranteed range.
• Peak Emission Wavelength (λ_p): Typically 650 nanometers (nm). This is the wavelength at which the optical power output is maximum.
• Dominant Wavelength (λ_d): Typically 639 nm. This is the wavelength perceived by the human eye and is the key metric for defining the color (Hyper Red).
• Spectral Line Half-Width (Δλ): Approximately 20 nm. This indicates the spectral purity or the spread of wavelengths emitted around the peak. A value of 20nm is characteristic of AlInGaP LEDs.
• Luminous Intensity Matching Ratio: Specified as a maximum of 2:1. This is a critical parameter for multi-digit displays or applications using multiple segments, ensuring that the brightness variation between the brightest and dimmest segment does not exceed this ratio, providing a uniform appearance.

2.2 Electrical Parameters

The electrical characteristics define the operating boundaries and typical conditions for the device.

• Forward Voltage per Segment (V_F): Typically 2.1V, with a maximum of 2.6V, measured at a forward current (I_F) of 20mA. This is the voltage drop across an illuminated segment. Designers must ensure the driving circuit can provide sufficient voltage.
• Continuous Forward Current per Segment (I_F): The absolute maximum rating is 25mA at 25°C. A derating factor of 0.33 mA/°C applies above 25°C, meaning the permissible continuous current decreases as ambient temperature rises to prevent overheating.
• Peak Forward Current: A pulsed current of up to 90mA is allowed under specific conditions (1/10 duty cycle, 0.1ms pulse width). This enables multiplexing schemes or short bursts of higher brightness.
• Reverse Voltage (V_R): Maximum 5V. Exceeding this can damage the LED junction. Circuit designs should incorporate protection if reverse voltage is possible.
• Reverse Current (I_R): Maximum 100 μA at the full reverse voltage of 5V, indicating the leakage current in the off state.
• Power Dissipation per Segment: Maximum 70 mW. This thermal limit, combined with the current derating, is crucial for reliability calculations.

2.3 Thermal and Environmental Ratings

• Operating Temperature Range: -35°C to +85°C. The device is rated for industrial-grade environments.
• Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: A maximum of 260°C for a maximum of 3 seconds, measured 1.6mm (1/16 inch) below the seating plane. This is a standard guideline for wave or reflow soldering processes to avoid thermal damage to the package or die.

3. Binning System Explanation

The datasheet explicitly states the device is \"categorized for luminous intensity.\" This refers to a common practice in LED manufacturing known as \"binning.\"

Due to inherent minor variations in the semiconductor epitaxial growth and fabrication process, LEDs from the same production batch can have slight differences in key parameters like luminous intensity and forward voltage. To ensure consistency for customers, manufacturers test each LED and sort them into different performance groups or \"bins.\" A product categorized for luminous intensity means the units are guaranteed to meet the specified intensity range (200-600 μcd in this case), and often, tighter bins within that range can be requested for high-uniformity applications. While not detailed in this brief datasheet, other common binning parameters can include dominant wavelength (for color consistency) and forward voltage.

4. Performance Curve Analysis

The datasheet references typical characteristic curves. While the specific graphs are not provided in the text, we can infer their standard content and significance based on the parameters listed.

4.1 Current vs. Voltage (I-V) Curve

A typical I-V curve would show the exponential relationship between forward current and forward voltage. The curve would pass through the typical V_F point of 2.1V at 20mA. This curve is essential for designing the current-limiting circuitry, whether using a simple resistor or a constant-current driver.

4.2 Luminous Intensity vs. Forward Current (I_V vs. I_F)

This graph would show how brightness increases with current. It is typically linear over a range but will saturate at higher currents due to thermal and efficiency droop. The curve would show the intensity at the test condition of 1mA and illustrate performance up to the maximum continuous current.

4.3 Temperature Dependence

Characteristic curves noted at temperatures other than 25°C would illustrate key dependencies:

• Forward Voltage vs. Temperature: For AlInGaP LEDs, V_F typically decreases with increasing temperature (negative temperature coefficient). This is important for thermal management and constant-current drive design.
• Luminous Intensity vs. Temperature: Output intensity generally decreases as junction temperature rises. The derating of continuous current is directly linked to managing this thermal effect to maintain brightness and longevity.

4.4 Spectral Distribution

A spectral plot would visualize the emitted light's power distribution across wavelengths, centered around 650nm (peak) with a 20nm half-width, confirming the Hyper Red color point.

5. Mechanical and Package Information

The device has a gray face with white segments, which enhances contrast by reducing ambient light reflection. The package dimensions are provided in millimeters with a standard tolerance of ±0.25mm. The exact footprint and pin spacing are critical for PCB layout. The internal circuit diagram confirms a common cathode configuration for all segments and the decimal points. This means all the cathodes (negative terminals) of the LED segments are connected internally to common pins (1 and 6), while each segment anode (positive terminal) has its own dedicated pin. This configuration is common and simplifies multiplexing in microcontroller-driven applications.

6. Pin Connection and Circuit Interface

The 10-pin device has the following pinout:

1. Common Cathode
2. Anode F (Top segment)
3. Anode G (Center segment)
4. Anode E (Bottom-left segment)
5. Anode D (Bottom segment)
6. Common Cathode (tied internally to pin 1)
7. Anode RDP (Right Decimal Point)
8. Anode C (Bottom-right segment)
9. Anode B (Top-right segment)
10. Anode A (Top segment)

Note: The datasheet also mentions \"Rt. and Lt. Hand Decimal,\" indicating the device includes both right and left decimal points, though only the right decimal point (RDP) anode is listed in the pin connection table. The left decimal point is likely internally connected to another segment anode or is not separately accessible in this version. The common cathode connection on pins 1 and 6 allows for flexibility in PCB routing and heat dissipation.

7. Soldering and Assembly Guidelines

The key guideline provided is the solder temperature limit: 260°C maximum for 3 seconds at 1.6mm below the seating plane. This aligns with standard IPC guidelines for through-hole components. For wave soldering, this means controlling preheat and contact time. For manual soldering, a temperature-controlled iron should be used to avoid prolonged heat application. Standard ESD (Electrostatic Discharge) precautions should be observed during handling, as LEDs are sensitive to static electricity. Storage should be within the specified temperature range in a low-humidity environment.

8. Application Suggestions and Design Considerations

8.1 Typical Application Scenarios

• Portable Multimeters and Test Equipment: Low current draw is ideal for battery life.
• Consumer Appliances: Timers, temperature readouts on ovens or heaters.
• Industrial Control Panels: Status indicators, counter displays.
• Automotive Aftermarket Displays: For auxiliary gauges (voltage, temperature).
• Educational Kits and Prototyping: Due to its simplicity and common interface.

8.2 Design Considerations

• Current Limiting: Always use a series resistor or constant-current driver for each segment anode. The resistor value can be calculated as R = (Supply Voltage - V_F) / I_F. For a 5V supply and targeting 10mA with a typical V_F of 2.1V: R = (5 - 2.1) / 0.01 = 290Ω. A 270Ω or 330Ω standard resistor would be suitable.
• Multiplexing: For multi-digit displays, a common cathode configuration is easily multiplexed. By sequentially enabling the common cathode of each digit and presenting the segment data for that digit, many digits can be controlled with fewer I/O pins. The peak current rating allows for higher pulsed currents during the multiplex cycle to achieve average brightness.
• Microcontroller Interface: Typically requires 8 I/O lines (7 segments + 1 decimal) per digit if not multiplexed, plus a transistor or driver IC to sink the common cathode current, which is the sum of currents for all lit segments in that digit.
• Viewing Angle: The wide viewing angle allows for flexible mounting positions, but for optimal readability, consider the primary user sightline.

9. Technical Comparison and Differentiation

Compared to older technologies like incandescent or vacuum fluorescent displays (VFDs), this LED display offers significantly lower power consumption, longer lifespan, and higher shock/vibration resistance. Within the LED display family, the use of AlInGaP for Hyper Red offers advantages over older GaAsP red LEDs, typically providing higher efficiency (more light per mA), better temperature stability, and a more saturated red color. The 0.3-inch size is smaller than common 0.5-inch or 0.56-inch displays, offering higher density or more compact designs. The low current requirement (effective even at 1mA) is a key differentiator for power-constrained designs compared to displays requiring 5-20mA per segment for standard brightness.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 What is the purpose of the two common cathode pins (1 and 6)?

They are internally connected. Providing two pins allows for better current distribution, reduces the current density per pin, aids in PCB layout flexibility (routing from either side), and can improve heat dissipation from the die.

10.2 Can I drive this display directly from a microcontroller pin?

You can connect the segment anodes to microcontroller output pins, but you must include a current-limiting resistor in series with each pin. The microcontroller pin alone cannot safely limit the current. Furthermore, the common cathode current (up to 25mA x number of lit segments) will likely exceed a single microcontroller pin's sink capability, requiring an external transistor or driver IC (like a ULN2003) to switch the cathode.

10.3 What does \"Hyper Red\" mean compared to standard Red?

\"Hyper Red\" is a marketing term often used for AlInGaP LEDs with a dominant wavelength around 630-640nm. It appears as a deeper, more orange-tinted red compared to the slightly longer wavelength (660-670nm) \"Deep Red\" or the shorter, more orange standard \"Red\" (620-625nm). It offers a good balance of visual brightness and color distinction.

10.4 How do I achieve uniform brightness across all digits in a multi-digit design?

Use the multiplexing technique and ensure the current-limiting resistors are identical for all corresponding segments across digits. The intensity matching ratio specification (2:1 max) on the datasheet helps, but for best results, use LEDs from the same production bin or implement software brightness calibration if your driver allows pulse-width modulation (PWM).

11. Design and Usage Case Example

Scenario: Designing a simple 3-digit voltmeter display.

1. Circuit Topology: Use three LTS-313AJD displays in a multiplexed configuration. The segment anodes (A-G, DP) of all three displays are connected in parallel. Each display's common cathode pins are connected to a separate NPN transistor (e.g., 2N3904) collector, with the emitter to ground. The transistor base is driven by a microcontroller pin via a base resistor.
2. Microcontroller Role: An ADC reads the voltage. The firmware converts the value to three digits. It then enters a fast loop: it turns off all cathode transistors, outputs the segment pattern for Digit 1 to the parallel anode lines (through series resistors), turns on the cathode transistor for Digit 1, waits a short time (e.g., 2ms), then repeats for Digit 2 and Digit 3. The cycle repeats fast enough (e.g., >60Hz) to appear as a steady, flicker-free display.
3. Calculations: If each segment is driven at 5mA during its active time, and three segments are lit per digit (e.g., showing \"1\"), the peak current per segment is 5mA. The average current per segment is 5mA / 3 (for 3-digit multiplex) ≈ 1.67mA, which is well within limits and conserves power. The cathode transistor must sink 3 segments * 5mA = 15mA, which is easily handled.

12. Operational Principle Introduction

A seven-segment LED display is an array of light-emitting diodes arranged in a figure-eight pattern. Each diode (segment) is a p-n junction semiconductor device. When a forward voltage exceeding the junction's threshold (approximately 2.1V for this AlInGaP type) is applied, electrons and holes recombine in the active region, releasing energy in the form of photons (light). The specific wavelength (color) of the light is determined by the bandgap energy of the semiconductor material, which is engineered in the AlInGaP compound. By selectively applying current to different combinations of the seven segments (A through G), the numerals 0-9 and some letters can be formed. The common cathode configuration internally connects all the negative sides of these diodes, simplifying external control.

13. Technology Trends and Context

Discrete seven-segment LED displays like this one represent a mature and reliable technology. Current trends in display technology are moving towards higher integration, such as multi-digit modules with built-in controllers (e.g., TM1637 or MAX7219 drivers) that communicate via I2C or SPI, drastically reducing the microcontroller I/O and software overhead. There is also a shift towards organic LED (OLED) and flexible displays for more complex graphics. However, for simple, bright, low-cost, and low-power numeric indication in harsh environments (wide temperature range, high brightness required), discrete LED segments remain a dominant and optimal solution. The ongoing development in LED materials, like more efficient AlInGaP and InGaN (for blue/green), continues to improve the efficiency, brightness, and color options for such displays.