LTD-322JG LED Display Datasheet - 0.3-inch Digit Height - Green (571nm) - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTD-322JG is a high-performance, solid-state numeric display component designed for applications requiring clear, bright, and reliable numerical readouts. Its primary function is to visually represent numeric data, typically digits 0 through 9, using a seven-segment configuration. The core technology is based on Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material, which is specifically engineered for high-efficiency light emission in the green-yellow spectrum. This device is categorized as a common cathode, duplex display, meaning it contains two independent digit elements within a single package, each sharing a common cathode connection point, which simplifies circuit design for multiplexing applications.

The display features a black face with white segments, a design choice that significantly enhances contrast and readability under various lighting conditions, even in brightly lit environments. The 0.3-inch (7.62 mm) digit height strikes a balance between being easily legible from a reasonable distance and maintaining a compact form factor suitable for integration into space-constrained electronic assemblies such as test equipment, industrial control panels, instrumentation, consumer appliances, and point-of-sale terminals.

2. Technical Parameters Deep Objective Interpretation

2.1 Optical Characteristics

The optical performance is defined by several key parameters measured under standardized test conditions. The Average Luminous Intensity (Iv) is specified with a typical value of 800 µcd at a forward current (IF) of 1 mA. This parameter indicates the perceived brightness of the lit segments by the human eye. The wide range (Min: 320 µcd, Typ: 800 µcd) suggests a binning system for intensity, which is common in LED manufacturing to group devices with similar output.

The Peak Emission Wavelength (λp) is 571 nanometers (nm), and the Dominant Wavelength (λd) is 572 nm, both measured at IF=20mA. These values place the emitted light firmly in the green color region. The Spectral Line Half-Width (Δλ) is 15 nm, which describes the spectral purity or the spread of wavelengths emitted; a narrower half-width indicates a more monochromatic, pure green color. The Luminous Intensity Matching Ratio is specified as 2:1 maximum. This is a critical parameter for multi-digit or multi-segment displays, ensuring that the brightness variation between different segments or digits does not exceed a 2-to-1 ratio, guaranteeing a uniform visual appearance.

2.2 Electrical Parameters

The electrical characteristics define the operating limits and conditions for the device. The Absolute Maximum Ratings set the boundaries for safe operation. The Continuous Forward Current per Segment is rated at 25 mA at 25°C, with a derating factor of 0.33 mA/°C. This means the maximum allowable continuous current decreases as the ambient temperature (Ta) increases above 25°C to prevent thermal damage. For pulsed operation, a Peak Forward Current of 60 mA is allowed under a 1/10 duty cycle with a 0.1 ms pulse width, useful for multiplexing schemes to achieve higher peak brightness.

The Forward Voltage per Segment (VF) has a typical value of 2.6V at IF=20mA (Max: 2.6V, Min: 2.05V). This is the voltage drop across the LED when it is conducting current and is essential for designing the current-limiting circuitry. The Reverse Voltage (VR) rating is 5V, indicating the maximum voltage that can be applied in the reverse-biased direction without causing breakdown. The Reverse Current (IR) is a leakage parameter, specified at a maximum of 100 µA at VR=5V.

2.3 Thermal Characteristics

The device is rated for an Operating Temperature Range of -35°C to +85°C and an identical Storage Temperature Range. This wide range ensures reliable operation in harsh environmental conditions, from industrial freezers to hot engine compartments. The Power Dissipation per Segment is 70 mW, which, combined with the forward voltage and current, dictates the thermal load. The specified Solder Temperature is a maximum of 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This is a critical parameter for wave soldering or reflow soldering processes to prevent damage to the LED chips or the epoxy package.

3. Binning System Explanation

While the datasheet does not explicitly detail a complex binning matrix, the specification ranges for key parameters imply a categorization process. The primary binning is likely for Luminous Intensity, as noted in the features (\"CATEGORIZED FOR LUMINOUS INTENSITY\"). Devices are tested and sorted into bins based on their measured Iv at 1 mA, ensuring customers receive displays with consistent brightness levels. There may also be implicit voltage binning, as the forward voltage has a specified range (2.05V to 2.6V). For color-critical applications, the tight specification on peak/dominant wavelength (571-572 nm) acts as a de facto single-bin system for color, ensuring a consistent green hue across all units.

4. Performance Curve Analysis

The datasheet references Typical Electrical / Optical Characteristic Curves. Although the specific curves are not provided in the text, standard LED curves can be inferred and are crucial for design. The Current vs. Voltage (I-V) Curve would show the exponential relationship, highlighting the turn-on voltage (~2V) and the operating region. The Luminous Intensity vs. Forward Current (Iv-IF) Curve is typically linear over a range, showing how brightness increases with current. Understanding this relationship is key for driving the LED at the desired brightness level while staying within power limits. The Luminous Intensity vs. Ambient Temperature (Iv-Ta) Curve would show a decrease in output as temperature rises, which is vital for designing systems that operate consistently across the specified temperature range. The Spectral Distribution Curve would visually represent the peak wavelength and spectral half-width.

5. Mechanical and Packaging Information

The device comes in a standard LED display package. The Package Dimensions drawing is referenced, with all dimensions provided in millimeters and standard tolerances of ±0.25 mm unless otherwise noted. This drawing is essential for PCB footprint design, ensuring proper hole placement, pad size, and component spacing. The Pin Connection table provides the critical interface definition. It is a 10-pin configuration: Pin 5 is the common cathode for Digit 2, Pin 10 is the common cathode for Digit 1, and Pins 1, 3, 4, 6, 7, 8, and 9 are the anodes for segments G, A, F, D, E, C, and B, respectively. Pin 2 is noted as \"No Pin,\" indicating it is a mechanical placeholder or non-connected pin. The Internal Circuit Diagram visually confirms the common cathode, duplex architecture, showing how the two digits' corresponding segments (e.g., segment \"A\" of digit 1 and digit 2) are internally connected to a single anode pin, which is standard for multiplexed displays.

6. Soldering and Assembly Guidelines

Adherence to the specified Solder Temperature limit (260°C max for 3 seconds) is paramount. This typically applies to wave soldering processes. For reflow soldering, a standard lead-free profile with a peak temperature not exceeding 260°C should be used, ensuring the time above liquidus is controlled. Prolonged exposure to high temperature can cause internal wire bond failure, epoxy cracking, or degradation of the LED chip's optical properties. It is recommended to avoid mechanical stress on the pins during insertion. The device should be stored in its original moisture-barrier bag until use to prevent moisture absorption, which can cause \"popcorning\" during soldering.

7. Application Suggestions

7.1 Typical Application Scenarios

This display is ideal for any application requiring a compact, bright, and reliable numeric readout. Common uses include: digital multimeters and test equipment, industrial process controllers and timers, medical device displays, automotive dashboard indicators (for non-critical information), household appliances (ovens, microwaves, washing machines), and commercial equipment like cash registers or weighing scales.

7.2 Design Considerations

Current Limiting: LEDs are current-driven devices. A series current-limiting resistor must be used for each anode or a constant current driver circuit must be implemented. The resistor value is calculated using Ohm's Law: R = (Vcc - VF) / IF, where Vcc is the supply voltage, VF is the forward voltage (use max value for worst-case current calculation), and IF is the desired forward current.

Multiplexing: The common cathode, duplex design is intended for multiplexed operation. By sequentially enabling one cathode (digit) at a time and presenting the segment data for that digit on the anode lines, multiple digits can be controlled with a reduced number of I/O pins from a microcontroller. The peak current rating allows for higher pulsed currents to compensate for the reduced duty cycle, maintaining perceived brightness.

Viewing Angle: The wide viewing angle feature ensures the display remains readable from various positions, which is important for panel-mounted devices.

8. Technical Comparison

The primary differentiator of the LTD-322JG is its use of AlInGaP technology for green emission. Compared to older technologies like Gallium Phosphide (GaP), AlInGaP offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current. The black face/white segment design provides superior contrast compared to displays with diffused or gray faces. The 0.3-inch digit height is a standard size, but its specific combination of high brightness, contrast, and AlInGaP efficiency may offer an advantage over similar-sized displays using less advanced semiconductor materials.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the \"No Pin\" connection?
A: Pin 2 is physically present but electrically disconnected. It likely serves as a mechanical key to ensure proper orientation during automated insertion or to provide structural symmetry.

Q: How do I achieve different brightness levels?
A: Brightness is primarily controlled by the forward current (IF). You can adjust the current-limiting resistor value or use a PWM (Pulse Width Modulation) signal on the anode or cathode. PWM is highly effective as it maintains the optimal forward voltage/current relationship while modulating the duty cycle.

Q: Can I connect the two common cathodes together?
A: No, they must be controlled separately for proper multiplexing. Connecting them together would cause both digits to display the same segment pattern simultaneously, defeating the purpose of a duplex display.

Q: What does the 2:1 Luminous Intensity Matching Ratio mean for my design?
A: It guarantees that all segments within a device will have reasonably uniform brightness. You do not need to design individual current adjustments for each segment to compensate for large intrinsic variations.

10. Practical Design and Usage Case

Consider designing a simple two-digit counter using a microcontroller. The microcontroller would have 7 I/O pins connected to the segment anodes (A-G) and 2 I/O pins connected to the digit cathodes (via NPN transistors or MOSFETs for current sinking). The firmware would implement a multiplexing routine: turn on the transistor for Digit 1, output the segment pattern for the first digit on the anode pins, wait a short interval (e.g., 5ms), then turn off Digit 1, turn on Digit 2, output the pattern for the second digit, and repeat. The current for each segment would be set by a single current-limiting resistor on the common anode line (if using a common positive supply) or individual resistors on each microcontroller pin, calculated based on the desired average current and accounting for the 1/2 duty cycle in this two-digit example.

11. Principle Introduction

The device operates on the principle of electroluminescence in a semiconductor p-n junction. The AlInGaP material is a direct bandgap semiconductor. When a forward voltage exceeding the junction's built-in potential is applied, electrons from the n-region and holes from the p-region are injected across the junction. These charge carriers recombine in the active region, releasing energy in the form of photons. The specific composition of the Aluminum, Indium, Gallium, and Phosphide atoms determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light. In this case, the composition is tuned to emit photons with a wavelength of approximately 571-572 nm, which is perceived as green light. The non-transparent GaAs substrate helps direct more of the generated light out through the top of the device, improving external efficiency.

12. Development Trends

In the field of indicator and display LEDs, ongoing trends include: Increased Efficiency: Continued material science improvements (e.g., more advanced epitaxial structures) to extract more light per unit of electrical input power. Miniaturization: Development of displays with smaller digit heights or higher pixel densities for portable devices. Integration: Combining the LED display with driver ICs and controllers into more complete module solutions to simplify end-user design. Color Expansion: While this is a monochrome green device, there is a broad trend towards full-color, addressable LED matrices and displays. For standard seven-segment displays, the focus remains on reliability, cost reduction, and achieving even higher brightness and contrast ratios for sunlight-readable applications.