LTS-3403LJG LED Display Datasheet - 0.8-inch Digit Height - Green AlInGaP - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTS-3403LJG is a high-performance, single-digit, seven-segment display module designed for clear numeric readouts in various electronic applications. Its primary function is to provide a highly legible digital character output. The core advantage of this device lies in its utilization of Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor technology for the LED chips. This material system is known for producing high-efficiency light emission in the green to red spectrum, offering superior brightness and color purity compared to older technologies. The display features a gray face with white segments, which enhances contrast and readability under various lighting conditions. Its low power consumption and compatibility with standard integrated circuits make it suitable for a wide target market, including consumer electronics, industrial instrumentation, test and measurement equipment, and embedded systems where reliable, low-power numeric indication is required.

2. Technical Parameter Deep Dive

2.1 Photometric and Optical Characteristics

The key performance metrics are defined under standard test conditions at an ambient temperature (Ta) of 25°C. The Average Luminous Intensity (Iv) is specified with a minimum of 320 µcd, a typical value of 900 µcd, and no stated maximum, when driven at a forward current (IF) of 1mA. This parameter indicates the perceived brightness of the lit segments. The light output is categorized, meaning devices are binned according to their measured luminous intensity, ensuring consistency in brightness levels for production batches.

The color characteristics are defined by wavelength. The Peak Emission Wavelength (λp) is typically 571 nanometers (nm) at IF=20mA, which places the emitted light firmly in the green region of the visible spectrum. The Dominant Wavelength (λd) is typically 572 nm, a closely related metric describing the perceived color. The Spectral Line Half-Width (Δλ) is typically 15 nm, indicating a relatively narrow spectral bandwidth, which contributes to a pure, saturated green color. Luminous intensity is measured using a sensor and filter calibrated to the CIE photopic eye-response curve, ensuring the values correspond to human visual perception.

2.2 Electrical Parameters

The electrical specifications define the operating limits and conditions. The Forward Voltage per Segment (VF) has a typical value of 2.6V and a maximum of 2.6V when IF=10mA. This is a critical parameter for designing the current-limiting circuitry. The Reverse Current per Segment (IR) is a maximum of 100 µA when a reverse voltage (VR) of 5V is applied, indicating the leakage current in the off-state.

The Absolute Maximum Ratings set the boundaries for safe operation. The maximum continuous forward current per segment is 25 mA. A derating factor of 0.33 mA/°C applies linearly from 25°C, meaning the allowable continuous current decreases as the ambient temperature rises above 25°C to prevent thermal damage. The maximum reverse voltage per segment is 5V. Exceeding these ratings may cause permanent damage to the device.

2.3 Thermal Characteristics

Thermal management is implied through the derating specification for continuous forward current. The device is rated for an Operating Temperature Range of -35°C to +85°C and an identical Storage Temperature Range. The Solder Temperature rating specifies that the device can withstand 260°C for 3 seconds at a point 1/16 inch (approximately 1.6mm) below the seating plane during wave or reflow soldering processes. Adherence to this guideline is crucial to prevent damage to the internal LED chips and wire bonds.

3. Binning System Explanation

The datasheet explicitly states that the device is categorized for luminous intensity. This means that during manufacturing, the LED displays are tested and sorted into different bins based on their measured light output at a standard test current (typically 1mA, as per the Iv specification). This binning process ensures that end-users receive products with consistent brightness levels, which is vital for applications where multiple digits are used side-by-side to avoid noticeable variations in segment intensity. While the document does not detail the specific bin codes or ranges, the practice guarantees a minimum level of performance (320 µcd) and groups devices with similar output characteristics together.

4. Performance Curve Analysis

The datasheet references Typical Electrical/Optical Characteristic Curves. Although the specific graphs are not provided in the text excerpt, such curves are standard in LED documentation. They typically include:

• Forward Current (IF) vs. Forward Voltage (VF) Curve: This shows the nonlinear relationship between current and voltage, essential for designing the correct driver circuit. The knee voltage is typically around the stated VF of 2.05-2.6V.
• Luminous Intensity (Iv) vs. Forward Current (IF) Curve: This graph illustrates how light output increases with drive current. It is generally linear over a range but will saturate at higher currents due to thermal and efficiency limits.
• Luminous Intensity vs. Ambient Temperature Curve: This demonstrates the thermal quenching effect, where LED light output decreases as the junction temperature increases. This reinforces the importance of the current derating specification.
• Spectral Distribution Curve: A plot of relative intensity versus wavelength, showing the peak at ~571nm and the narrow half-width, confirming the pure green color emission.

These curves provide designers with a deeper understanding of the device's behavior under non-standard conditions, enabling more robust and optimized system design.

5. Mechanical and Package Information

The device is provided with a detailed package dimension drawing. All dimensions are specified in millimeters with a standard tolerance of ±0.25mm unless otherwise noted. This drawing is critical for PCB (Printed Circuit Board) layout, ensuring the footprint and keep-out areas are correctly designed. The display is designed for easy mounting on a P.C. board or socket, suggesting it has pins suitable for through-hole soldering or insertion into a compatible socket. The physical description notes a gray face and white segments, which is a key mechanical feature affecting aesthetics and readability.

6. Pin Connection and Internal Circuit

The LTS-3403LJG is a common cathode type display. This means the cathodes (negative terminals) of all LED segments are connected together internally and brought out to common pins, while each segment's anode (positive terminal) has its own dedicated pin. The pin connection table lists 17 pins, with several marked as \"NO PIN\" (presumably unused or mechanically present only). The active pins control segments A through G, two decimal points (Left and Right Decimal Point, L.D.P and R.D.P), and five common cathode connections (pins 4, 6, 12, 17, and one implied by the common cathode description). The internal circuit diagram would visually represent this common cathode architecture, showing how the multiple cathode pins are internally tied together to distribute current and potentially aid in heat dissipation.

7. Soldering and Assembly Guidelines

The primary guideline provided is the solder temperature specification: 260°C for 3 seconds at 1/16 inch below the seating plane. This is a standard JEDEC profile for wave or reflow soldering of through-hole components. Designers must ensure their assembly process complies with this limit to avoid thermal shock, which can crack the epoxy package or damage the semiconductor die. General handling should follow standard ESD (Electrostatic Discharge) precautions for semiconductor devices. The storage conditions are defined by the storage temperature range of -35°C to +85°C.

8. Application Suggestions

8.1 Typical Application Scenarios

This display is ideal for any application requiring a single, highly visible numeric digit. Common uses include: panel meters for voltage, current, or temperature; digital clocks and timers; scoreboard units; production counters; status indicator codes on appliances or industrial equipment; and as part of larger multi-digit displays in systems where digits are multiplexed.

8.2 Design Considerations

• Current Limiting: Always use series current-limiting resistors for each segment anode. The resistor value is calculated based on the supply voltage (Vcc), the LED forward voltage (VF, use max of 2.6V for reliability), and the desired forward current (IF, staying below 25mA continuous). Formula: R = (Vcc - VF) / IF.
• Driver Circuitry: As a common cathode display, the cathodes are typically connected to ground or switched to ground by a driver IC (like a 7-segment decoder/driver or a microcontroller GPIO pin configured as a sink). The anodes are driven high through the current-limiting resistors.
• Multiplexing: For multi-digit systems using similar displays, multiplexing is a common technique to control many segments with fewer I/O pins. This involves rapidly cycling power to each digit's common cathode while presenting the corresponding segment data on the shared anode lines. The LTS-3403LJG's low power consumption and compatibility make it suitable for multiplexed applications.
• Viewing Angle: The datasheet claims a wide viewing angle, which should be verified in the mechanical drawing or confirmed for the specific application's needs.

9. Technical Comparison and Differentiation

The key differentiators of the LTS-3403LJG are its use of AlInGaP technology and its specific 0.8-inch digit height. Compared to older technologies like standard GaP or GaAsP LEDs, AlInGaP offers significantly higher luminous efficiency, resulting in brighter displays at the same current or similar brightness at lower power. The 0.8-inch (20.32mm) height is a standard size offering a good balance between visibility and board space usage. The gray face/white segment design improves contrast compared to all-black or all-green packages. Its common cathode configuration is the most common and is widely supported by driver ICs and microcontroller libraries.

10. Frequently Asked Questions (FAQ)

Q: What is the purpose of having multiple common cathode pins (e.g., pins 4, 6, 12, 17)?
A: Multiple cathode pins help distribute the total return current from all lit segments, reducing current density in any single pin and PCB trace. This improves reliability and may aid in heat dissipation from the LED chip. They are internally connected, so electrically they are the same node.

Q: Can I drive this display directly from a 5V microcontroller pin?
A: No. You must always use a current-limiting resistor in series with each segment. Connecting a 5V source directly to the anode (with cathode grounded) would attempt to draw a very large current, potentially destroying the LED segment and damaging the microcontroller pin.

Q: What does \"Luminous Intensity Matching Ratio (IV-m) of 2:1\" mean?
A: This specifies the maximum allowable ratio between the brightest and dimmest segment within a single device when measured under the same conditions (IF=1mA). A ratio of 2:1 means the brightest segment will be no more than twice as bright as the dimmest segment, ensuring uniformity across the digit.

Q: How do I calculate the appropriate current-limiting resistor?
A: Use Ohm's Law: R = (Vsupply - VF) / IF. For example, with a 5V supply (Vsupply), a max VF of 2.6V, and a desired IF of 10mA (0.01A): R = (5 - 2.6) / 0.01 = 240 Ohms. A standard 220 or 270 Ohm resistor would be suitable.

11. Design and Usage Case Study

Consider designing a simple digital voltmeter displaying 0-9.9V. The system uses a microcontroller with an analog-to-digital converter (ADC) to measure voltage. The microcontroller's firmware reads the ADC, converts the value to two BCD (Binary-Coded Decimal) digits, and drives two LTS-3403LJG displays in a multiplexed configuration. One display shows the tens place (0-9) and the other shows the ones place and the decimal point. The common cathodes of each display are connected to separate microcontroller pins configured as open-drain/low-output sinks. The seven segment anodes (A-G) and the right decimal point anode are connected to other microcontroller pins through individual 220-ohm current-limiting resistors, shared between both displays. The firmware rapidly switches which display's cathode is grounded while outputting the segment pattern for that specific digit. This approach uses only 8 pins for segments + 2 pins for digit control = 10 I/O pins, instead of the 16+ pins required for static driving. The AlInGaP technology ensures the reading is bright and clear even in well-lit environments.

12. Technical Principle Introduction

The LTS-3403LJG is based on Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor technology. This is a III-V compound semiconductor where the bandgap energy--the energy difference between the valence band and conduction band--can be tuned by adjusting the ratios of Aluminum, Indium, Gallium, and Phosphorus. For green emission, the bandgap is engineered to be approximately 2.2-2.3 electron volts (eV). When a forward voltage exceeding the diode's turn-on voltage is applied, electrons and holes are injected into the active region where they recombine. This recombination releases energy in the form of photons (light). The wavelength (λ) of the emitted photon is inversely proportional to the bandgap energy (Eg), as described by the equation λ = hc/Eg (where h is Planck's constant and c is the speed of light). The specific composition results in photons with a wavelength around 571-572 nm, which the human eye perceives as green light. The non-transparent GaAs substrate absorbs some emitted light, but the design and materials still yield high efficiency and brightness.

13. Technology Trends

The evolution of seven-segment displays mirrors advancements in LED technology. Early displays used GaAsP or GaP, which had limited efficiency and color range. AlInGaP, introduced in the 1990s, represented a major leap, offering high efficiency and excellent color saturation in the red-orange-yellow-green spectrum. For pure green and blue, Indium Gallium Nitride (InGaN) technology later became dominant and is now standard for white LEDs as well. Current trends in numeric displays include: a shift towards surface-mount device (SMD) packages for automated assembly, though through-hole types like this remain popular for prototyping and certain industries; the integration of driver ICs and controllers directly into the display module (intelligent displays); the use of higher density matrices for alphanumeric and dot-matrix displays replacing simple seven-segment units in many applications; and a continued focus on increased efficiency (lumens per watt) and lower operating voltages to meet energy-saving regulations and battery-life demands. While newer technologies exist, AlInGaP-based displays like the LTS-3403LJG remain a cost-effective and highly reliable solution for monochromatic green numeric indication where their specific performance characteristics are optimal.