LTS-3403LJF LED Display Datasheet - 0.8-inch Digit Height - Yellow Orange Color - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTS-3403LJF is a single-digit, seven-segment alphanumeric display module designed for applications requiring clear, reliable numeric or limited alphanumeric indication. Its primary function is to provide a visual output for digital data from microcontrollers, logic circuits, or other driver ICs. The core advantage of this device lies in its use of Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor technology for the LED chips, which offers superior efficiency and color purity in the yellow-orange spectrum compared to older technologies like GaAsP. The device features a gray face with white segment markings, providing excellent contrast for the illuminated segments. It is categorized for luminous intensity, ensuring consistency in brightness across production batches. The display is designed for easy integration, suitable for mounting directly onto printed circuit boards (PCBs) or into compatible sockets, making it ideal for industrial control panels, test equipment, consumer appliances, and instrumentation where a single-digit readout is required.

1.1 Core Features and Target Market

The LTS-3403LJF is engineered with several key features that define its application space. The 0.8-inch (20.32 mm) digit height offers a balance between visibility and compactness, suitable for panel-mounted devices where space is a consideration but readability is paramount. The continuous uniform segments ensure a cohesive and professional appearance when lit. Its low power consumption and low power requirement make it compatible with battery-powered devices or systems where power efficiency is critical. The excellent character appearance and wide viewing angle are direct results of the AlInGaP chip technology and the diffused lens design, allowing the display to be read clearly from various angles. The solid-state reliability inherent to LED technology ensures a long operational lifetime with no moving parts to wear out. Finally, being I.C. compatible means it can be driven directly by standard digital logic outputs or through dedicated display driver integrated circuits with appropriate current-limiting resistors. The target market includes designers of portable electronic devices, embedded systems, automotive dashboards (for non-critical indicators), medical devices, and any electronic system requiring a durable, low-power numeric display.

2. Technical Parameter Deep Dive

The datasheet provides comprehensive electrical, optical, and thermal specifications that are critical for proper circuit design and reliable operation.

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's function. The Average Luminous Intensity (Iv) is specified with a minimum of 320 \u00b5cd, a typical value of 900 \u00b5cd, and no stated maximum, all measured at a forward current (If) of 1 mA. This parameter indicates the perceived brightness of a single segment. The low test current highlights the device's efficiency. The color characteristics are defined by three wavelength parameters. The Peak Emission Wavelength (\u03bbp) is typically 611 nm, measured at If=20mA. The Spectral Line Half-Width (\u0394\u03bb) is typically 17 nm, indicating the spectral purity or how narrow the range of emitted light is around the peak; a smaller value denotes a more monochromatic color. The Dominant Wavelength (\u03bbd) is typically 605 nm. It's important to note that the luminous intensity is measured using a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring the measurement correlates with human visual perception. The Luminous Intensity Matching Ratio (Iv-m) is specified as 2:1 maximum, meaning the brightness difference between the brightest and dimmest segment in a single unit will not exceed a factor of two, ensuring uniform appearance.

2.2 Electrical Parameters

The electrical specifications define the operating limits and conditions for the LED segments. The Absolute Maximum Ratings set the boundaries for safe operation. The Power Dissipation per Segment is 70 mW. The Peak Forward Current per Segment is 60 mA, but this is only permissible under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width) to manage heat. The Continuous Forward Current per Segment is 25 mA at 25\u00b0C, with a derating factor of 0.33 mA/\u00b0C. This means the maximum allowable continuous current decreases as ambient temperature increases above 25\u00b0C to prevent overheating. The Reverse Voltage per Segment is 5 V; exceeding this can damage the LED junction. Under standard operating conditions (Ta=25\u00b0C), the Forward Voltage per Segment (Vf) is typically 2.6 V with a maximum of 2.6 V at a test current of 10 mA. The minimum is listed as 2.05 V. The Reverse Current per Segment (Ir) is a maximum of 100 \u00b5A when a reverse voltage (Vr) of 5 V is applied, indicating the leakage current in the off state.

2.3 Thermal and Environmental Specifications

Reliability under various environmental conditions is crucial. The Operating Temperature Range is specified from -35\u00b0C to +85\u00b0C. This wide range allows the display to function in harsh environments, from industrial freezers to hot engine compartments. The Storage Temperature Range is identical (-35\u00b0C to +85\u00b0C), defining safe conditions when the device is not powered. A critical parameter for assembly is the Solder Temperature. The datasheet specifies that the device can withstand a temperature of 260\u00b0C for 3 seconds at a point 1/16 inch (approximately 1.59 mm) below the seating plane. This is a standard reference for wave soldering or reflow soldering processes, and designers must ensure their PCB assembly profile does not exceed these limits to avoid damaging the internal wire bonds or the LED chips themselves.

3. Binning System Explanation

The datasheet indicates that the device is \"Categorized for Luminous Intensity.\" This refers to a binning or sorting process performed during manufacturing. Due to natural variations in the semiconductor epitaxial growth and chip fabrication processes, LEDs from the same production batch can have slight variations in key parameters like luminous intensity and forward voltage. To ensure consistency for the end user, manufacturers test each unit and sort them into different \"bins\" based on measured performance. The LTS-3403LJF is binned specifically for luminous intensity. This means when a designer orders a quantity of these displays, the variation in brightness from one unit to another will be within a pre-defined, controlled range (implied by the 2:1 matching ratio within a unit, and further controlled across units by binning). This is essential for applications where multiple digits are used side-by-side, as it prevents noticeable brightness differences between displays. The datasheet does not specify separate bins for wavelength (color) or forward voltage, suggesting tight process control on these parameters or that binning is primarily focused on intensity for this product.

4. Performance Curve Analysis

While the datasheet lists a page for \"Typical Electrical / Optical Characteristic Curves,\" the provided content does not include the actual graphs. Typically, such curves are invaluable for design. One would expect to see a Forward Current vs. Forward Voltage (I-V) curve, which shows the non-linear relationship between current and voltage across the LED junction. This curve helps designers select the appropriate current-limiting resistor value for a given supply voltage. A Relative Luminous Intensity vs. Forward Current curve would show how brightness increases with current, often in a sub-linear fashion, helping to optimize the trade-off between brightness and power consumption/efficiency. A Relative Luminous Intensity vs. Ambient Temperature curve is critical for understanding how brightness degrades as the operating temperature rises, which is vital for designing systems that operate over the full temperature range. Finally, a Spectral Distribution graph would visually depict the intensity of light emitted across different wavelengths, centered around the 611 nm peak, showing the shape and width of the emission spectrum. Designers should consult the full datasheet from the manufacturer for these graphical representations to make informed decisions about drive current and thermal management.

5. Mechanical and Packaging Information

The mechanical design ensures reliable physical integration. The Package Dimensions diagram (not fully detailed in the text) would provide all critical measurements for PCB footprint design, including overall length, width, and height, the spacing between pins (pitch), the diameter and position of any mounting holes, and the distance from the bottom of the package to the seating plane. The Pin Connection table is the functional map of the 17-pin package. It reveals this is a Common Cathode configuration (pins 4, 6, 12, 17), where the negative side (cathode) of all LED segments is connected together internally. The anodes for each segment (A, B, C, D, E, F, G) and the left and right decimal points (L.D.P, R.D.P) are brought out to separate pins. Several pins (1, 8, 9, 16) are listed as \"NO PIN,\" meaning they are physically present but not electrically connected (likely for mechanical stability in the socket or during soldering). The polarity is clearly indicated by the common cathode designation. The gray face and white segments provide the visual interface.

6. Soldering and Assembly Guidelines

Proper handling during assembly is critical to long-term reliability. The key guideline provided is the Solder Temperature specification: 260\u00b0C for 3 seconds at 1/16 inch below the seating plane. This is a directive for wave soldering. For reflow soldering, a standard lead-free profile peaking at 260\u00b0C would be applicable, but the time above liquidus (e.g., 217\u00b0C) should be controlled to minimize thermal stress. Designers should ensure the PCB pad layout matches the recommended footprint from the dimensional drawing to prevent tombstoning or misalignment. The device should be stored in its original moisture-barrier bag until use, especially if it is not intended for immediate assembly, to prevent moisture absorption that could cause \"popcorning\" during reflow. The operating and storage temperature ranges (-35\u00b0C to +85\u00b0C) should be respected throughout the supply chain and product lifecycle. Avoid applying mechanical stress to the lens or pins during handling.

7. Application Suggestions

7.1 Typical Application Circuits

The LTS-3403LJF, being a common-cathode display, is typically driven by a \"sourcing\" driver. This means the microcontroller or driver IC pins connect to the segment anodes and source current to turn them on, while the common cathode pin(s) are connected to ground, usually through a transistor that can handle the combined segment current. A basic circuit involves connecting each anode pin to a GPIO pin of a microcontroller via a current-limiting resistor. The value of this resistor (R) is calculated using Ohm's Law: R = (Vcc - Vf) / If, where Vcc is the supply voltage (e.g., 5V or 3.3V), Vf is the forward voltage of the LED (typically 2.6V), and If is the desired forward current (e.g., 10-20 mA). For example, with a 5V supply and a target current of 15 mA: R = (5 - 2.6) / 0.015 = 160 ohms. A 150-ohm resistor would be a standard value. The common cathode pin(s) would be connected to an NPN transistor's collector, with the emitter to ground. The microcontroller would turn the transistor on to enable the digit. For multi-digit multiplexing (not applicable for a single digit, but for understanding), the anodes of corresponding segments across digits are tied together, and each digit's common cathode is controlled separately, illuminating one digit at a time in rapid succession.

7.2 Design Considerations and Notes

Several important considerations must be addressed. Current Limiting: Never connect an LED directly to a voltage source without a current-limiting resistor or constant-current driver, as the LED will draw excessive current and fail. Heat Dissipation: While LEDs are efficient, the power dissipated (P = Vf * If) per segment can be up to 65 mW (2.6V * 25mA). In applications where many segments are lit continuously, ensure adequate ventilation or heatsinking if operating near the maximum temperature. Viewing Angle: The wide viewing angle is beneficial, but for optimal readability, consider the primary user sightline when positioning the display in the enclosure. ESD Protection: AlInGaP LEDs can be sensitive to electrostatic discharge. Implement standard ESD handling precautions during assembly. Decoupling and Noise: In electrically noisy environments, consider adding a small decoupling capacitor (e.g., 100 nF) near the display's power connections to stabilize the supply.

8. Technical Comparison and Differentiation

The LTS-3403LJF differentiates itself primarily through its semiconductor material: AlInGaP. Compared to older red LEDs based on Gallium Arsenide Phosphide (GaAsP), AlInGaP offers significantly higher luminous efficacy (more light output per unit of electrical power), better temperature stability of color and brightness, and a more saturated, pure color in the amber/yellow-orange/red part of the spectrum. Compared to white LEDs (typically blue LED + phosphor), it offers a single, narrow-band emission which can be advantageous in applications where specific wavelength filtering is used or where color purity is desired without the broad spectrum of white light. Its 0.8-inch size fills a niche between smaller indicators and larger, power-hungry displays. The common cathode configuration is standard and offers compatibility with a vast array of driver ICs and microcontroller port configurations designed for common-cathode multiplexing.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the difference between Peak Wavelength (611 nm) and Dominant Wavelength (605 nm)?
A: Peak Wavelength is the single wavelength at which the emission spectrum has its maximum intensity. Dominant Wavelength is the single wavelength of monochromatic light that would appear to have the same color as the LED's output to the human eye. They often differ slightly. Dominant wavelength is more relevant for color specification.

Q: Can I drive this display with a 3.3V microcontroller?
A: Yes, but you must check the forward voltage. The typical Vf is 2.6V. With a 3.3V supply, the voltage drop across the current-limiting resistor would only be 0.7V (3.3V - 2.6V). To achieve a 15mA current, you would need a resistor of R = 0.7V / 0.015A = 46.7 ohms. This is feasible, but the current will be more sensitive to variations in Vf. It's generally acceptable, but verify brightness meets your needs.

Q: Why are there four common cathode pins?
A: Having multiple cathode pins helps distribute the total current drawn when all segments are lit. The sum of currents for 7 segments plus decimal points could exceed 200 mA. Spreading this current across multiple pins and PCB traces reduces current density, minimizes voltage drop, and improves reliability.

Q: What does \"I.C. COMPATIBLE\" mean?
A: It means the electrical characteristics of the LED (forward voltage, current requirements) are within ranges that can be directly driven by the output pins of standard digital integrated circuits (like CMOS or TTL logic chips or microcontroller GPIOs) when used with an appropriate current-limiting resistor. It does not mean you can connect it directly without a resistor.

10. Design and Usage Case Study

Consider designing a simple digital thermostat controller. The system uses a microcontroller to read a temperature sensor and display the setpoint or current temperature on a single digit (for simplicity, showing tens of degrees, or a code). The LTS-3403LJF is chosen for its clarity, low power (important for a device that may be battery-backed), and wide viewing angle (mounted on a wall). The microcontroller runs at 5V. The designer calculates resistor values for a segment current of 12 mA to balance brightness and power: R = (5V - 2.6V) / 0.012A = 200 ohms. Seven 200-ohm resistors are used, one for each segment anode (A-G). The common cathode pins are tied together and connected to the collector of a 2N3904 NPN transistor. The transistor's emitter goes to ground, and its base is driven by a microcontroller GPIO pin via a 10k resistor. To display a number, the microcontroller sets the pattern of segment anode pins high (through the resistors) and turns on the transistor to complete the circuit to ground. The yellow-orange color is easily visible in typical indoor lighting conditions. The robust temperature rating ensures the display functions reliably even if the thermostat is placed in a hot attic or a cold garage.

11. Operating Principle Introduction

The LTS-3403LJF operates on the fundamental principle of electroluminescence in a semiconductor p-n junction. The device uses Aluminum Indium Gallium Phosphide (AlInGaP) as the active semiconductor material. This compound is grown epitaxially on a non-transparent Gallium Arsenide (GaAs) substrate. When a forward voltage exceeding the material's bandgap voltage (around 2.0-2.2V for AlInGaP) is applied across the p-n junction, electrons from the n-type region and holes from the p-type region are injected into the active region. When these charge carriers recombine, they release energy. In a direct bandgap semiconductor like AlInGaP, this energy is released primarily in the form of photons (light). The specific wavelength of the emitted light (in this case, yellow-orange, around 611 nm) is determined by the bandgap energy of the AlInGaP alloy composition, which is carefully controlled during manufacturing. The gray face and white segments act as a diffuser and contrast filter, respectively, shaping the light output into recognizable numeric segments.

12. Technology Trends and Context

The LTS-3403LJF represents a mature and optimized technology. AlInGaP LEDs, developed in the 1990s, largely replaced GaAsP for high-efficiency red, orange, and yellow indicators and displays. The trend in display technology has since moved towards higher-density solutions like dot-matrix OLEDs, micro-LEDs, and LCDs for complex graphics. However, for simple, rugged, low-cost, and ultra-reliable single-digit or multi-digit numeric display needs, seven-segment LED displays remain highly relevant. Their advantages include extreme simplicity of control, very high brightness and contrast, wide operating temperature range, instant-on capability, and longevity measured in tens of thousands of hours. Current developments in this niche focus on even higher efficiency, allowing lower drive currents for the same brightness (extending battery life), and the integration of the driver circuitry directly into the display package (so-called \"intelligent displays\"). The core principle of a reliable, solid-state light source for numeric indication, as embodied by the LTS-3403LJF, continues to be a fundamental building block in electronic design across countless industries.