LTS-3403JF 0.8-Inch Yellow-Orange LED Display Datasheet - Digit Height 20.32mm - Forward Voltage 2.6V - Power 70mW - English Technical Document

1. Product Overview

The LTS-3403JF is a single-digit, seven-segment alphanumeric display module designed for applications requiring clear, bright numeric readouts. Its primary function is to visually represent numbers (0-9) and some letters using individually addressable LED segments. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material, specifically engineered to emit light in the yellow-orange spectrum. This material choice offers a balance of efficiency, brightness, and color purity. The device is categorized as a common cathode type, meaning all the cathodes (negative terminals) of the LED segments are connected internally, simplifying circuit design for microcontroller-based systems where segments are typically driven by sourcing current.

2. In-Depth Technical Parameter Analysis

2.1 Optical Characteristics

The optical performance is central to the display's functionality. The Average Luminous Intensity (Iv) is specified between 320 and 700 microcandelas (μcd) at a forward current (I_F) of 1mA. This range indicates a production binning process, where devices are sorted based on measured output. The Peak Emission Wavelength (λ_p) is 611 nanometers (nm), and the Dominant Wavelength (λ_d) is 605 nm, both measured at I_F=20mA. The dominant wavelength is the color perceived by the human eye. The Spectral Line Half-Width (Δλ) of 17 nm describes the purity of the emitted color; a narrower width indicates a more monochromatic, pure color. The Luminous Intensity Matching Ratio of 2:1 (max) ensures visual uniformity by limiting the brightness variation between different segments of the same digit.

2.2 Electrical Characteristics

The electrical parameters define the operating boundaries and power requirements. The Forward Voltage per Segment (V_F) is typically 2.6V with a maximum of 2.6V at I_F=20mA. This value is crucial for designing current-limiting resistors in the drive circuit. The Reverse Current per Segment (I_R) is a maximum of 100 μA at a Reverse Voltage (V_R) of 5V, indicating the device's leakage characteristics when reverse-biased, which is generally negligible in normal operation.

2.3 Absolute Maximum Ratings and Thermal Considerations

These ratings define the stress limits beyond which permanent damage may occur. The Continuous Forward Current per Segment is 25 mA at 25°C, with a derating factor of 0.33 mA/°C. This means the maximum safe current decreases as ambient temperature (T_a) increases above 25°C. For example, at 85°C, the maximum current would be approximately 25 mA - (0.33 mA/°C * 60°C) = 5.2 mA. The Power Dissipation per Segment is 70 mW, calculated as V_F * I_F. The Peak Forward Current for pulsed operation (1/10 duty cycle, 0.1ms pulse width) is 90 mA, allowing for brief over-driving to achieve higher peak brightness. The operating and storage temperature range is -35°C to +85°C.

3. Binning System Explanation

The datasheet explicitly states the device is "Categorized for Luminous Intensity." This refers to a post-production sorting (binning) process based on measured light output. Units are tested at the standard condition (I_F=1mA), and grouped into bins according to their Iv value (e.g., 320-450 μcd, 450-580 μcd, 580-700 μcd). This ensures consistency within a production batch. While not explicitly detailed for voltage or wavelength in this document, such categorization is common in LED manufacturing to provide predictable performance for designers.

4. Performance Curve Analysis

While the specific curves are not detailed in the provided text, typical performance curves for such a device would include:

• I-V (Current-Voltage) Curve: Shows the exponential relationship between forward voltage and current. The knee voltage (where current begins to rise sharply) is typically around 1.8-2.0V for AlInGaP LEDs.
• Luminous Intensity vs. Forward Current (I_v vs. I_F): This curve is generally linear at lower currents but may saturate at higher currents due to thermal and efficiency droop.
• Luminous Intensity vs. Ambient Temperature (I_v vs. T_a): Shows how light output decreases as junction temperature increases. AlInGaP LEDs typically have better high-temperature performance compared to some other materials.
• Spectral Distribution: A graph plotting relative intensity against wavelength, showing the peak at 611 nm and the 17 nm half-width.

5. Mechanical and Package Information

The device features a standard 0.8-inch (20.32 mm) digit height. The package has a light gray face and white segment color when unlit, which enhances contrast when the yellow-orange segments are illuminated. The dimensional drawing (referenced in the PDF) provides critical measurements for PCB footprint design and panel cutouts. All dimensions are in millimeters with a standard tolerance of ±0.25 mm unless otherwise specified. The 18-pin dual-in-line package is a common footprint for such displays.

6. Pin Connection and Internal Circuit

The pinout is defined for an 18-pin package. Key connections are: Anodes for segments A, F, E, L.D.P. (Left Decimal Point), R.D.P. (Right Decimal Point), and D. Cathodes for segments C, G, and B. There are multiple Common Cathode pins (pins 4, 6, 17) which are internally connected, providing flexibility for PCB layout. Pin 12 is listed as "COMMON ANODE," which appears to be an error or specific to a different variant, as the device is described as a Common Cathode type. The internal circuit diagram shows the standard common cathode configuration for a seven-segment plus two decimal point display.

7. Soldering and Assembly Guidelines

The datasheet specifies a maximum soldering temperature of 260°C for a maximum of 3 seconds, measured at 1.6mm (1/16 inch) below the seating plane. This is a typical reflow or hand-soldering guideline intended to prevent thermal damage to the LED chips, wire bonds, and plastic package. It is critical to adhere to this profile to maintain reliability. Standard ESD (Electrostatic Discharge) precautions should be observed during handling.

8. Application Suggestions

8.1 Typical Application Scenarios

• Test and Measurement Equipment: Digital multimeters, power supplies, frequency counters.
• Consumer Electronics: Audio equipment (amplifiers, receivers), kitchen appliances, clocks.
• Industrial Controls: Panel meters, process indicators, timer displays.
• Automotive Aftermarket: Gauges and readouts (where environmental specs are suitable).

8.2 Design Considerations

• Current Limiting: External resistors are mandatory for each segment anode (or for the common cathode) to set the operating current. Calculate using R = (V_supply - V_F) / I_F.
• Multiplexing: For multi-digit displays, multiplexing is common. The LTS-3403JF's low current requirement (down to 1mA per segment) is advantageous here, as it allows for higher peak currents during the short multiplexed "on" time to achieve desired average brightness without exceeding average power limits.
• Viewing Angle: The wide viewing angle is beneficial for panels where the user may not be directly in front of the display.
• Microcontroller Drive: Most modern microcontrollers can source/sink sufficient current (20mA per pin is common) to drive these LEDs directly, often requiring simple transistor buffers for the common cathode due to higher total current.

9. Technical Comparison and Differentiation

The key differentiators of the LTS-3403JF within its category are:

• Material (AlInGaP): Offers higher efficiency and better temperature stability compared to older GaAsP (Gallium Arsenide Phosphide) red/yellow LEDs, and a distinct color compared to InGaN (Indium Gallium Nitride) blue/green/white LEDs.
• Very Low Current Operation: The specification of operation down to 1mA per segment is a significant feature for battery-powered or ultra-low-power designs, where every milliamp counts.
• High Contrast Package: The light gray face with white segments provides excellent off-state contrast, improving readability in various lighting conditions.
• Categorized Luminous Output: Provides predictability for the designer, ensuring consistent appearance across units in a product.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display with a 3.3V microcontroller power supply?
A: Yes. With a typical V_F of 2.6V, a 3.3V supply provides adequate headroom (0.7V) for a current-limiting resistor. At I_F=10mA, R = (3.3V - 2.6V) / 0.01A = 70 Ohms.

Q: What is the purpose of having multiple common cathode pins?
A> They are internally connected. Providing multiple pins helps distribute the total cathode current (which can be 7x I_F or more when all segments are on), reduces current density per pin, and aids in PCB layout and heat dissipation.

Q: How do I achieve uniform brightness if the luminous intensity has a 2:1 matching ratio?
A> The 2:1 ratio is a maximum limit between the brightest and dimmest segment on a single device. In practice, variation is usually less. For critical applications, use a constant current driver or PWM (Pulse Width Modulation) to digitally calibrate each segment's brightness.

Q: Can I use this outdoors?
A> The operating temperature range (-35°C to +85°C) is wide, but the datasheet does not specify an IP (Ingress Protection) rating for water or dust. For outdoor use, the display would require additional sealing or housing to protect against moisture.

11. Practical Design Case Study

Scenario: Designing a 4-digit voltmeter readout using multiplexing with a 5V supply and a microcontroller.

1. Current Selection: Choose I_F = 5mA per segment for a good balance of brightness and power. Peak current during multiplexing will be higher (e.g., 20mA if using a 25% duty cycle per digit).
2. Resistor Calculation: For static drive: R = (5V - 2.6V) / 0.005A = 480 Ohms (use 470 Ohms standard value).
3. Multiplexing Drive: To achieve an average of 5mA, the peak current during the active time slot needs to be 20mA (5mA / 0.25 duty cycle). Recalculate resistor: R = (5V - 2.6V) / 0.020A = 120 Ohms. Verify this peak current is within the absolute maximum ratings for pulsed operation (90mA).
4. Circuit: Connect segment anodes to microcontroller I/O pins via the 120-ohm resistors. Connect the four common cathode pins (one per digit) to the collector of NPN transistors (e.g., 2N3904). The transistor bases are driven by microcontroller pins via base resistors. The microcontroller sequentially turns on one digit transistor and sets the pattern on the segment lines.
5. Software: Implement a timer interrupt to refresh the display at a rate high enough to avoid flicker (typically >60Hz).

12. Operating Principle

The device operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's turn-on voltage (approximately 1.8-2.0V for AlInGaP) is applied, electrons from the n-type material and holes from the p-type material are injected into the active region (the quantum wells in the AlInGaP layer). 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 in turn dictates the wavelength (color) of the emitted light—in this case, yellow-orange. The non-transparent GaAs substrate helps reflect light upward, improving overall light extraction efficiency from the top of the chip.

13. Technology Trends

While discrete seven-segment LED displays remain relevant for specific applications, broader trends in display technology include:

• Integration: Movement towards displays with integrated driver ICs (I2C, SPI) to reduce microcontroller pin count and simplify software.
• Material Advancements: Ongoing research into more efficient phosphor-converted LEDs and direct-color semiconductors to expand color gamut and efficiency.
• Alternative Technologies: In many consumer applications, seven-segment displays are being replaced by dot-matrix OLED or LCD modules that offer greater flexibility (full alphanumerics, graphics) in a similar footprint, though often at a higher cost and power consumption for the equivalent brightness.
• Application Shift: The primary application for devices like the LTS-3403JF is increasingly in industrial, instrumentation, and legacy equipment where simplicity, robustness, high brightness, and wide viewing angles are prioritized over graphical capability.

The LTS-3403JF represents a mature, optimized solution within its niche, offering reliable performance based on well-understood AlInGaP technology.