LTS-3403JS LED Display Datasheet - 0.8-inch Digit Height - AlInGaP Yellow - 2.6V Forward Voltage - 40mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-3403JS is a monochromatic, seven-segment alphanumeric display module designed for applications requiring clear, bright numeric readouts. Its primary function is to visually represent digits (0-9) and some limited characters through the selective illumination of its individual LED segments. The core technology is based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material, which is engineered to emit light in the yellow wavelength region. This specific material choice offers a balance of efficiency, brightness, and color purity. The device is categorized as a common cathode type, meaning the cathodes (negative terminals) of the LED segments are connected together internally, simplifying the driving circuitry when using sink-current drivers. The physical design features a light gray faceplate with white segment outlines, enhancing contrast and readability when the segments are illuminated.

2. In-Depth Technical Parameter Analysis

This section provides a detailed breakdown of the device's operational limits and performance characteristics under specified conditions.

2.1 Absolute Maximum Ratings

These parameters define the stress limits beyond which permanent damage to the device may occur. Operation at or near these limits is not recommended for reliable performance.

• Power Dissipation per Segment: 40 mW. This is the maximum amount of electrical power that can be converted into heat and light by a single segment without risk of damage.
• Peak Forward Current per Segment: 60 mA. This current is permissible only under pulsed conditions with a 1/10 duty cycle and a 0.1 ms pulse width. It is used for brief, high-intensity flashes.
• Continuous Forward Current per Segment: 25 mA at 25°C. This rating decreases linearly at a rate of 0.33 mA/°C as the ambient temperature (Ta) rises above 25°C, a process known as derating.
• Reverse Voltage per Segment: 5 V. Exceeding this voltage in the reverse bias direction can cause junction breakdown.
• Operating & Storage Temperature Range: -35°C to +85°C. The device is rated to function and be stored within this environmental temperature range.
• Solder Temperature: Maximum of 260°C for a maximum of 3 seconds, measured 1.6mm (1/16 inch) below the seating plane of the component during wave or reflow soldering.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at an ambient temperature (Ta) of 25°C under the specified test conditions.

• Average Luminous Intensity (I_V): Ranges from 320 μcd (min) to 700 μcd (max), with a typical value implied, when driven at a forward current (I_F) of 1 mA per segment. This is a measure of the perceived brightness of the light output.
• Peak Emission Wavelength (λ_p): 588 nm (typical). This is the wavelength at which the optical output power is greatest, defining the yellow color.
• Spectral Line Half-Width (Δλ): 15 nm (typical). This indicates the spectral purity; a smaller value means a more monochromatic (pure) yellow color.
• Dominant Wavelength (λ_d): 587 nm (typical). This is the wavelength perceived by the human eye, closely matching the peak wavelength.
• Forward Voltage per Segment (V_F): Ranges from 2.05 V (min) to 2.6 V (max) at I_F = 20 mA. This is the voltage drop across the LED when it is conducting.
• Reverse Current per Segment (I_R): 100 μA (max) when a reverse voltage (V_R) of 5 V is applied.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (max). This specifies the maximum allowable brightness variation between different segments of the same digit or between digits, ensuring uniform appearance.

Note on Measurement: Luminous intensity is measured using a sensor and filter combination that approximates the photopic (daylight-adapted) spectral sensitivity of the human eye, as defined by the CIE (International Commission on Illumination).

3. Binning System Explanation

The datasheet indicates the device is "Categorized for Luminous Intensity." This refers to a post-production sorting process known as "binning." During manufacturing, slight variations in the epitaxial growth and processing of the AlInGaP material can lead to differences in key parameters like forward voltage (V_F) and luminous intensity (I_V). To ensure consistency for the end-user, manufactured units are tested and sorted into specific "bins" or groups based on these measured values. For the LTS-3403JS, the primary binning criterion is luminous intensity at 1 mA, as evidenced by the specified min (320 μcd) and max (700 μcd) values. This allows designers to select parts from a specific intensity bin if their application requires tightly matched brightness levels across multiple displays.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristic Curves." While the specific graphs are not detailed in the provided text, standard curves for such devices typically include:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the exponential relationship. The curve will indicate the typical V_F at common drive currents like 1 mA and 20 mA.
• Luminous Intensity vs. Forward Current: Demonstrates how light output increases with current, usually in a near-linear relationship within the operating range, before potentially saturating at very high currents.
• Luminous Intensity vs. Ambient Temperature: Illustrates the decrease in light output as the junction temperature rises, a critical factor for thermal management in high-brightness or high-temperature applications.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at ~588 nm and the half-width, confirming the yellow color emission.

These curves are essential for designers to model the display's behavior under different operating conditions not explicitly covered in the table.

5. Mechanical & Package Information

5.1 Package Dimensions

The device has a defined physical outline. All dimensions are provided in millimeters (mm) with a standard tolerance of ±0.25 mm (0.01 inches) unless otherwise noted on the dimensional drawing. The key feature is the 0.8-inch digit height, which corresponds to 20.32 mm, defining the character size.

5.2 Pin Configuration and Internal Circuit

The LTS-3403JS is housed in an 18-pin package. The pinout is as follows: Pins 4, 6, 12, and 17 are Common Anodes. Segment cathodes are assigned to specific pins: A(2), B(15), C(13), D(11), E(5), F(3), G(14). Additionally, it features both Left (L.D.P, pin 7) and Right (R.D.P, pin 10) Decimal Points. Pins 1, 8, 9, 16, and 18 are noted as "No Pin" (likely unused or mechanically present only). The internal circuit diagram shows a common cathode configuration for the main digit segments, meaning all segment cathodes are separate, and the anodes are common. The decimal points are individually accessible.

6. Soldering & Assembly Guidelines

The absolute maximum ratings provide the key soldering parameter: the device can withstand a maximum temperature of 260°C for up to 3 seconds during the soldering process. This is typical for wave soldering or infrared reflow profiles. It is crucial that this thermal limit is not exceeded to prevent damage to the internal wire bonds, the LED chip, or the plastic package. Designers should follow standard JEDEC or IPC guidelines for PCB footprint design, ensuring proper pad size and spacing to facilitate good solder joint formation and avoid bridging. The device should be stored in its original moisture-barrier bag until use to prevent moisture absorption, which can cause "popcorning" (package cracking) during reflow.

7. Application Recommendations

7.1 Typical Application Scenarios

The LTS-3403JS is suited for a wide range of applications requiring clear, reliable numeric displays, including:

• Test and Measurement Equipment: Multimeters, frequency counters, power supplies.
• Industrial Controls: Panel meters, process indicators, timer displays.
• Consumer Electronics: Audio equipment (amplifiers, receivers), kitchen appliances.
• Automotive Aftermarket: Gauges and readouts (where environmental specs are met).
• Low-Power Portable Devices: Where its excellent low-current performance (down to 1mA/segment) is a significant advantage for battery life.

7.2 Design Considerations

• Current Limiting: LEDs are current-driven devices. A series current-limiting resistor is mandatory for each common anode or a constant-current driver must be used to prevent exceeding the maximum continuous current, especially since V_F can vary.
• Multiplexing: For multi-digit displays, multiplexing (rapidly cycling power between digits) is common to reduce pin count and power. The LTS-3403JS's common cathode design is well-suited for this. The peak current rating (60mA) allows for higher pulsed currents during multiplexing to achieve perceived brightness.
• Viewing Angle: The "wide viewing angle" feature is beneficial for applications where the display may be viewed from off-axis positions.
• Thermal Management: While low power, in high-ambient-temperature environments or when driven at higher currents, attention should be paid to the derating curve for continuous current.

8. Technical Comparison & Differentiation

The key differentiating advantages of the LTS-3403JS based on its datasheet are:

• Material (AlInGaP): Compared to older technologies like GaAsP, AlInGaP offers significantly higher luminous efficiency and better temperature stability, resulting in brighter and more consistent output.
• Low Current Operation: Its characterization and testing for excellent performance at currents as low as 1 mA per segment make it stand out for ultra-low-power applications where other displays might be dim or unstable.
• Segment Matching: The device is tested for segment matching, ensuring uniform brightness across all segments of a digit, which is critical for professional-grade appearance.
• High Contrast Package: The light gray face with white segments provides high contrast even when unpowered, improving overall readability.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display directly from a 5V microcontroller pin?
A: No. The typical forward voltage is 2.05-2.6V. Connecting it directly to 5V without a current-limiting resistor would cause excessive current flow, destroying the LED. A series resistor must be calculated based on the supply voltage (e.g., 5V), the LED V_F, and the desired I_F.

Q: What is the difference between "Peak Wavelength" and "Dominant Wavelength"?
A: Peak wavelength is the physical peak of the emitted light spectrum. Dominant wavelength is the single wavelength perceived by the human eye that matches the color of the light. For a monochromatic source like this yellow LED, they are very close (587nm vs 588nm).

Q: The maximum continuous current is 25mA, but the test condition for V_F is 20mA. Which should I use for design?
A: 20mA is a standard test condition and a common operating point for good brightness. You can design for 20mA. The 25mA rating is the absolute maximum; designing near this limit without thermal consideration is not advised for long-term reliability.

Q: How do I use the left and right decimal points?
A: They are independent LEDs. Pin 7 (L.D.P) is the cathode for the left decimal point, and Pin 10 (R.D.P) is for the right. To illuminate one, you must connect its cathode pin to ground (through a resistor) and supply voltage to one of the common anodes (pins 4, 6, 12, 17).

10. Practical Design Example

Scenario: Designing a single-digit voltmeter readout powered by a 5V supply, targeting a segment current of 10 mA for adequate brightness.

1. Circuit Configuration: Use a common cathode configuration. Connect all segment cathodes (A-G, DP) to individual I/O pins of a microcontroller via current-limiting resistors. Connect all four common anodes (pins 4, 6, 12, 17) together to the 5V supply rail.
2. Resistor Calculation: Assuming a worst-case V_F of 2.6V at 10mA. Resistor Value R = (V_supply - V_F) / I_F = (5V - 2.6V) / 0.01A = 240 Ohms. A standard 220 or 270 Ohm resistor would be suitable. Power dissipation in the resistor P = I²R = (0.01)² * 240 = 0.024W, so a standard 1/4W resistor is fine.
3. Microcontroller Interface: To display a number (e.g., '7'), the microcontroller would set its pins connected to segments A, B, and C to a logic LOW (sinking current), while keeping the others HIGH. This completes the circuit from 5V (anode) through the LED and resistor to the microcontroller's ground, lighting segments A, B, and C.
4. Multiplexing Extension: For a 4-digit display, you would have four LTS-3403JS units. Connect all corresponding segment cathodes together (all 'A' pins together, etc.). Each display's common anodes would be controlled separately by a transistor switch. The microcontroller rapidly cycles through enabling one digit's anode at a time while outputting the segment pattern for that digit. The persistence of vision makes all digits appear lit simultaneously.

11. Operating Principle

The LTS-3403JS operates on the principle of electroluminescence in a semiconductor p-n junction. The active material is AlInGaP. When a forward voltage exceeding the junction's threshold (approximately 2V) is applied, 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 the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly dictates the wavelength (color) of the emitted photons—in this case, yellow light around 587-588 nm. Each segment of the digit is a separate LED with its own p-n junction. The common cathode configuration means the n-side (cathode) of all these junctions for the main digit are connected internally, while the p-sides (anodes) are separate for individual segment control.

12. Technology Trends

While discrete seven-segment LED displays like the LTS-3403JS remain relevant for specific applications due to their simplicity, high brightness, and robustness, broader display technology trends have shifted. For complex alphanumeric or graphical information, dot-matrix LED displays, OLEDs, and LCDs are now predominant due to their flexibility. However, in the niche of high-brightness, low-power, simple numeric indicators, AlInGaP and especially newer AllnGaP-on-GaP (transparent substrate) technologies continue to offer superior efficiency and brightness compared to older materials. The trend in such discrete displays is towards higher efficiency (more light per mA), lower operating voltages, and potentially multi-color or RGB-capable single packages, although monochromatic displays like this one will persist for cost-sensitive and reliability-critical applications where their specific advantages are paramount.