LTD-4608JG 0.4-inch Dual Digit LED Display Datasheet - Digit Height 10.0mm - Green Color - English Technical Documentation

1. Product Overview

The LTD-4608JG is a compact, high-performance dual-digit seven-segment display designed for applications requiring clear numeric readouts with low power consumption. Its primary function is to provide a visual numeric output in electronic devices such as instrumentation panels, test equipment, consumer electronics, and industrial controls. The core advantage of this device lies in its use of advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material for the LED chips, which offers superior efficiency and color purity compared to older technologies. The target market includes designers and engineers working on portable devices, battery-powered equipment, and any application where space, power efficiency, and readability are critical constraints.

1.1 Key Features and Core Advantages

• 0.4-inch (10.0-mm) Digit Height: Provides a character size suitable for medium-range viewing distances, balancing visibility and component footprint.
• Continuous Uniform Segments: Ensures a smooth, professional appearance of the displayed numerals without visible gaps or irregularities in the light emission.
• Low Power Requirement: Engineered for energy efficiency, making it ideal for battery-operated devices. It operates at a typical forward current of 1mA for standard luminous intensity measurement.
• High Brightness & High Contrast: The AlInGaP material and the gray face with white segments create excellent luminosity and a sharp contrast ratio, ensuring readability even in well-lit ambient conditions.
• Wide Viewing Angle: Offers consistent light output and color across a broad viewing angle, enhancing usability from various perspectives.
• Solid-State Reliability: As an LED-based device, it offers long operational life, shock resistance, and fast switching times compared to mechanical or other display technologies.
• Categorized for Luminous Intensity: Units are binned according to their light output, allowing for consistent brightness matching in multi-digit or multi-device applications.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed analysis of the electrical and optical characteristics defined in the datasheet, explaining their significance for design and application.

2.1 Absolute Maximum Ratings

These are stress limits that must not be exceeded under any conditions to prevent permanent damage to the device.

• Power Dissipation per Segment: 70 mW. This is the maximum power that can be safely dissipated by a single LED segment as heat.
• Peak Forward Current per Segment: 60 mA (at 1/10 duty cycle, 0.1ms pulse width). This rating is for brief pulsed operation, useful for multiplexing or achieving higher instantaneous brightness.
• Continuous Forward Current per Segment: 25 mA (at 25°C). This is the maximum DC current for continuous operation. The datasheet specifies a derating factor of 0.33 mA/°C above 25°C, meaning the allowable continuous current decreases as ambient temperature rises to manage thermal load.
• Reverse Voltage per Segment: 5 V. Exceeding this voltage in reverse bias can damage the LED junction.
• Operating & Storage Temperature Range: -35°C to +85°C. The device is rated for industrial-grade temperature environments.
• Solder Temperature: 260°C for 3 seconds at 1/16 inch (approx. 1.6mm) below the seating plane. This defines the reflow soldering profile to avoid thermal damage during assembly.

2.2 Electrical & Optical Characteristics (at Ta=25°C)

These are the typical performance parameters under specified test conditions.

• Average Luminous Intensity (Iv): 320 to 850 µcd (min to max) at a forward current (IF) of 1mA. This wide range indicates the binning process; designers must account for this variation or select binned parts for uniform appearance. The typical value is likely around the middle of this range.
• Peak Emission Wavelength (λp): 571 nm (typical). This is the wavelength at which the emitted light intensity is highest, placing it in the pure green region of the visible spectrum.
• Spectral Line Half-Width (Δλ): 15 nm (typical). This measures the spectral purity. A narrower half-width indicates a more monochromatic, saturated green color.
• Dominant Wavelength (λd): 572 nm (typical). This is the single wavelength perceived by the human eye, closely matching the peak wavelength for this device.
• Forward Voltage per Segment (VF): 2.05V to 2.6V (typical) at IF=20mA. This is the voltage drop across an LED segment when conducting. It is crucial for designing the current-limiting circuitry. The variation is due to normal semiconductor manufacturing tolerances.
• Reverse Current per Segment (IR): 100 µA (max) at VR=5V. This is the small leakage current when the LED is reverse-biased at its maximum rating.
• Luminous Intensity Matching Ratio (Iv-m): 2:1 (max). This specifies the maximum allowable ratio between the brightest and dimmest segment within a single device or between devices from the same bin, ensuring visual uniformity.

3. Binning System Explanation

The datasheet indicates the device is \"Categorized for Luminous Intensity.\" This refers to a post-production sorting (binning) process.

• Luminous Intensity Binning: As shown by the Iv range (320-850 µcd @1mA), LEDs are sorted into groups based on their measured light output. This allows manufacturers to offer parts with guaranteed minimum brightness or to sell parts within tighter intensity ranges for a premium. Designers should specify the required bin or be prepared for brightness variation in their bill of materials.
• Wavelength/Color Binning: While not explicitly detailed with multiple codes, the tight typical specifications for λp (571nm) and λd (572nm) suggest a controlled manufacturing process. For critical color applications, parts may be available in specific wavelength bins.
• Forward Voltage Binning: The VF range (2.05-2.6V) represents the natural spread. For applications where power supply design is extremely sensitive, selecting parts from a specific voltage bin can be beneficial.

4. Performance Curve Analysis

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

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph shows how light output increases with current. It is generally linear at lower currents but may saturate at higher currents due to thermal effects. The 1mA test point for Iv indicates operation in the efficient, linear region.
• Forward Voltage vs. Forward Current: Shows the exponential relationship, critical for designing constant-current drivers.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates how light output decreases as temperature increases. This is a key consideration for high-temperature environments.
• Spectral Distribution: A plot of light intensity versus wavelength, showing the peak at ~571nm and the narrow half-width, confirming the pure green color.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Drawing

The device has a standard 10-pin dual in-line package (DIP). Key dimensional notes from the datasheet: all dimensions are in millimeters, with standard tolerances of ±0.25mm (0.01\") unless otherwise specified. The drawing would detail the overall length, width, height, digit spacing, segment dimensions, and pin spacing (likely a standard 0.1\" / 2.54mm pitch).

5.2 Pin Connection and Polarity Identification

The device uses a common anode configuration for multiplexing. The internal circuit diagram shows two common anodes (one for each digit) and individual cathodes for each segment (A-G and DP).

Pinout:
1: Cathode C
2: Cathode D.P. (Decimal Point)
3: Cathode E
4: Common Anode (Digit 2)
5: Cathode D
6: Cathode F
7: Cathode G
8: Cathode B
9: Common Anode (Digit 1)
10: Cathode A

Polarity is clearly marked by the \"Common Anode\" designation. The physical package likely has a notch or dot near pin 1 for orientation.

6. Soldering and Assembly Guidelines

• Reflow Soldering Parameters: As per the Absolute Maximum Ratings, the recommended soldering profile is 260°C for 3 seconds, measured at a point 1.6mm below the package body. This is a standard lead-free reflow condition.
• Precautions:
  • Avoid mechanical stress on the pins during insertion.
  • Ensure the soldering iron tip temperature is controlled to prevent exceeding the maximum package temperature.
  • Use appropriate flux and cleaning procedures if necessary.
• Storage Conditions: Store in a dry, anti-static environment within the specified temperature range (-35°C to +85°C). Avoid exposure to high humidity or corrosive gases.

7. Packaging and Ordering Information

• Packaging Specification: Typically, such displays are supplied in anti-static tubes or trays to protect the pins and lens from damage and electrostatic discharge (ESD).
• Model Numbering Rule: The part number LTD-4608JG likely follows an internal coding system where \"LTD\" signifies the product family (LED display), \"4608\" indicates the size and type (0.4\" 2-digit), and \"JG\" specifies the color (Green) and possibly other variants like right-hand decimal (as noted in the description).

8. Application Recommendations

8.1 Typical Application Scenarios

• Digital multimeters and clamp meters
• Bench power supplies and electronic loads
• Process control indicators
• Fitness equipment displays
• Automotive aftermarket gauges (for interior use)
• Consumer appliance timers and counters

8.2 Design Considerations

• Drive Circuitry: Use constant current drivers or current-limiting resistors for each cathode line. For multiplexing the two digits, switch the common anodes (pins 4 and 9) sequentially at a frequency high enough to avoid flicker (typically >60Hz).
• Current Calculation: Based on the desired brightness and the VF curve. For example, to achieve typical brightness at 1mA with a 5V supply and a VF of 2.3V, the current-limiting resistor would be R = (V_supply - VF) / I_F = (5 - 2.3) / 0.001 = 2700 Ω.
• Microcontroller Interface: The cathodes can be driven directly by microcontroller GPIO pins (sink current) if the current per segment is within the MCU's sink capability, or through transistor/MOSFET arrays for higher currents.
• Viewing Angle: Leverage the wide viewing angle by mounting the display perpendicular to the primary user sightline.

9. Technical Comparison and Differentiation

Compared to older technologies like standard GaP (Gallium Phosphide) green LEDs or red GaAsP LEDs, the AlInGaP-based LTD-4608JG offers:

• Higher Efficiency and Brightness: More light output per milliamp of current.
• Superior Color Saturation: A narrower spectral half-width results in a purer, more visually distinct green.
• Better Temperature Stability: AlInGaP generally maintains its performance better over temperature ranges than some older materials.
• Compared to modern white LED backlit LCDs, this device offers higher contrast in direct sunlight, lower power consumption for simple numeric readouts, and extreme simplicity of interface (direct drive vs. LCD controller).

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: What is the purpose of the \"Luminous Intensity Matching Ratio\" of 2:1?
A1: This ratio ensures visual consistency. It means that within one display unit, no segment will be more than twice as bright as the dimmest segment. This prevents unevenly lit numbers, which could be mistaken for a different digit (e.g., an \"8\" with a dim segment looking like a \"0\").

Q2: Can I drive this display with a 3.3V microcontroller system?
A2: Yes, but careful design is needed. The typical VF is 2.05-2.6V. At 3.3V supply, the voltage headroom for a current-limiting resistor is very small (3.3 - 2.6 = 0.7V). You must calculate the resistor value precisely (e.g., for 1mA: R = 0.7V / 0.001A = 700Ω). Ensure the MCU pin can sink the required current. A constant current driver IC is often a more reliable solution for low-voltage supplies.

Q3: Why are there two different current ratings (Continuous 25mA and Peak 60mA)?
A3: The 25mA continuous rating is for DC operation, limited by average heat dissipation. The 60mA peak rating allows for higher instantaneous brightness in a multiplexed system. In multiplexing, each digit is only powered for a fraction of the time (duty cycle). The higher peak current during its \"on\" time creates a brighter perceived average brightness, while the lower average current keeps the device within its thermal limits.

11. Practical Design and Usage Case Study

Case: Designing a Simple 2-Digit Voltmeter Readout
A designer is creating a compact voltmeter to display 0.0V to 9.9V. They select the LTD-4608JG for its small size, low power, and clear green display. The system uses a microcontroller with an analog-to-digital converter (ADC) to measure voltage.

• Circuit Design: The microcontroller's port pins are connected to the segment cathodes (A-G, DP) via 220Ω current-limiting resistors (calculated for ~3mA per segment at 5V). Two other GPIO pins drive PNP transistors (or P-channel MOSFETs) that switch the common anodes (Digit 1 and Digit 2) to the 5V supply.
• Software: The firmware reads the ADC, converts the value to two BCD digits, and uses a look-up table to determine which segments to illuminate for each digit (0-9). It then multiplexes: it turns on the transistor for Digit 1, sets the cathode patterns for the first digit, waits 5ms, turns off Digit 1, turns on the transistor for Digit 2, sets the cathode patterns for the second digit, waits 5ms, and repeats. This 100Hz refresh rate eliminates visible flicker.
• Result: A clear, stable two-digit readout consuming minimal microcontroller resources and power.

12. Operating Principle Introduction

The LTD-4608JG operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the junction's built-in potential (approximately 2V for AlInGaP) is applied, electrons from the n-type region and holes from the p-type region recombine in the active region. In AlInGaP LEDs, this recombination releases energy primarily in the form of photons with a wavelength corresponding to the green part of the spectrum (~571nm). The specific alloy composition of Aluminum, Indium, Gallium, and Phosphide determines the bandgap energy and thus the color of the emitted light. The non-transparent GaAs substrate helps reflect light upward, improving overall light extraction efficiency from the top surface. The seven segments are individual LED chips wired in the pattern of a digit, allowing any number from 0 to 9 (and some letters) to be formed by selectively energizing combinations of these segments.

13. Technology Trends and Developments

While seven-segment LED displays remain a robust and cost-effective solution for numeric readouts, the broader display technology field is evolving. Trends relevant to this product's domain include:

• Increased Efficiency: Ongoing research in semiconductor materials, including further refinements to AlInGaP and development of materials like InGaN for other colors, continues to push the lumens-per-watt efficiency higher, enabling brighter displays at lower currents.
• Miniaturization: There is a constant drive for smaller pixel pitches and higher density, though for standard seven-segment displays, the 0.4\" size represents a well-established sweet spot for many applications.
• Integration: Some modern displays integrate the driver IC and even a microcontroller interface (like I2C or SPI) directly into the package, simplifying the external circuit design. The LTD-4608JG represents the traditional, discrete approach which offers maximum flexibility and lower cost for high-volume, cost-sensitive designs.
• Competition from Alternative Technologies: OLED (Organic LED) displays offer excellent contrast and viewing angles and are becoming more affordable for small, custom-shaped displays. However, for simple, high-brightness, low-power numeric indicators, traditional LED segment displays like the LTD-4608JG maintain significant advantages in longevity, ruggedness, and sunlight readability.