LTS-4710AJD LED Display Datasheet - 0.4-inch Digit Height - AlInGaP Red - Low Power - English Technical Document

1. Product Overview

The LTS-4710AJD is a single-digit, seven-segment display designed for applications requiring clear numeric readouts with minimal power consumption. Its core technology is based on high-efficiency Aluminum Indium Gallium Phosphide (AlInGaP) LED chips, which are mounted on a non-transparent Gallium Arsenide (GaAs) substrate. The display features a gray face with white segment markings, enhancing contrast and readability. The primary design goal is to deliver excellent visual performance under low driving currents, making it suitable for battery-powered or energy-conscious devices.

1.1 Core Advantages and Target Market

The device offers several key advantages that define its market position. It features a 0.4-inch (10.16 mm) digit height, providing a balance between size and visibility. The segments are continuous and uniform, ensuring a consistent and professional appearance. A major selling point is its low power requirement; it is specifically tested and characterized for operation at currents as low as 1 mA per segment, with segment matching ensured even at these levels. This results in high brightness, high contrast, and a wide viewing angle. Combined with solid-state reliability, these features make the LTS-4710AJD ideal for portable instrumentation, consumer electronics, industrial control panels, and any application where power efficiency and clear numeric display are critical.

2. Technical Parameters Deep Dive

This section provides a detailed, objective analysis of the device's specifications as defined in the datasheet.

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operating conditions must stay within these boundaries.

• Power Dissipation per Segment: 70 mW maximum.
• Peak Forward Current per Segment: 100 mA, applicable under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width).
• Continuous Forward Current per Segment: 25 mA at 25°C. This rating derates linearly at 0.33 mA/°C as ambient temperature (Ta) increases above 25°C.
• Reverse Voltage per Segment: 5 V maximum.
• Operating & Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: The device can withstand 260°C for 3 seconds at a distance of 1/16 inch (approx. 1.59 mm) below the seating plane.

2.2 Electrical & Optical Characteristics

These parameters are measured at an ambient temperature (Ta) of 25°C and define the typical performance of the device.

• Average Luminous Intensity (I_V): Ranges from 200 μcd (min) to 650 μcd (max), with a typical value provided, when driven at a forward current (I_F) of 1 mA. This confirms its low-current capability.
• Peak Emission Wavelength (λ_p): Typically 656 nm, placing the output in the red region of the visible spectrum.
• Spectral Line Half-Width (Δλ): Typically 22 nm, indicating the spectral purity of the AlInGaP material.
• Dominant Wavelength (λ_d): Typically 640 nm.
• Forward Voltage per Segment (V_F): Ranges from 2.1 V (min) to 2.6 V (max) at I_F = 20 mA.
• Reverse Current per Segment (I_R): Maximum 100 μA when a reverse voltage (V_R) of 5 V is applied.
• Luminous Intensity Matching Ratio (I_V-m): Maximum 2:1 between segments when driven at I_F = 10 mA, ensuring uniform brightness across the digit.

Note: Luminous intensity measurement follows a standard approximating the CIE photopic eye-response curve.

3. Binning System Explanation

The datasheet indicates that the device is \"categorized for luminous intensity.\" This implies a binning process where units are sorted based on their measured light output at a specific test current (likely 1 mA or 10 mA). This allows designers to select displays with consistent brightness levels for their application, preventing noticeable variations between digits in a multi-digit display. The specific bin code or intensity ranges are not detailed in this document but would typically be part of the ordering information.

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:

• I-V (Current-Voltage) Curve: Shows the relationship between forward voltage (V_F) and forward current (I_F). For AlInGaP LEDs, this curve has a turn-on voltage around 1.8-2.0V and then a relatively linear region.
• Luminous Intensity vs. Forward Current (I_V vs. I_F): This graph is crucial for low-current design. It shows how light output increases with current. The curve is generally linear at lower currents but may saturate at higher currents due to thermal effects.
• Luminous Intensity vs. Ambient Temperature: Shows how light output decreases as the junction temperature rises. This is critical for understanding performance in elevated temperature environments.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at ~656 nm and the 22 nm half-width.

5. Mechanical & Package Information

5.1 Package Dimensions

The device comes in a standard LED display package. All dimensions are in millimeters (mm) with a general tolerance of ±0.25 mm unless otherwise specified. Key dimensions include the overall height, width, and depth of the package, the digit window size, and the lead (pin) spacing and length. The exact numerical values from the dimension drawing are not provided in the text extract but are essential for PCB footprint design.

5.2 Pin Connection and Polarity Identification

The LTS-4710AJD is a common anode display. It has a 14-pin configuration, though not all pins are used.

• Anode Pins: Pins 3 and 14 are common anodes. They must be connected to the positive supply voltage.
• Cathode Pins: Each segment (A, B, C, D, E, F, G, and Decimal Point DP) has its own cathode pin. These pins are connected to ground (or a current sink) to illuminate the corresponding segment.
• No-Connection (NC) Pins: Pins 4, 5, 6, and 12 are not internally connected. They can be left floating or used for mechanical stability during soldering.

The internal circuit diagram shows the common anode connection to pins 3 and 14, with individual LEDs for each segment connected between this common node and their respective cathode pins.

6. Soldering & Assembly Guidelines

Based on the absolute maximum ratings:

• Reflow Soldering: The device can withstand a peak temperature of 260°C for 3 seconds, measured 1.59 mm (1/16\") below the package body. Standard lead-free reflow profiles with a peak around 245-250°C are typically suitable, but the specific thermal mass of the board must be considered.
• Hand Soldering: If hand soldering is necessary, a temperature-controlled iron should be used with a quick operation time (less than 3 seconds per pin) to avoid excessive heat transfer to the LED chips.
• Storage Conditions: Store in an environment within the storage temperature range of -35°C to +85°C. It is advisable to keep the devices in their original moisture-barrier bags until use to prevent moisture absorption, which can cause \"popcorning\" during reflow.

7. Application Suggestions

7.1 Typical Application Scenarios

• Portable Multimeters & Test Equipment: The low current draw directly extends battery life.
• Consumer Electronics: Clocks, timers, kitchen appliances, and audio equipment where a bright, clear numeric display is needed.
• Industrial Instrumentation: Panel meters, counters, and process control displays where reliability and visibility are key.
• Automotive Aftermarket Displays: For auxiliary gauges and readouts (ensuring operating temperature range compatibility).

7.2 Design Considerations

• Current Limiting: Always use series current-limiting resistors for each segment cathode (or a constant current driver). Calculate the resistor value using R = (V_supply - V_F) / I_F. For low-current operation at 1-2 mA, ensure the driver circuit can provide stable current at these levels.
• Multiplexing: For multi-digit displays, multiplexing is common. The LTS-4710AJD's common anode structure is well-suited for this. The peak current rating (100 mA pulsed) allows for higher instantaneous currents during multiplexing to achieve desired average brightness, but duty cycle and pulse width must be carefully managed.
• Viewing Angle: The wide viewing angle allows for flexible placement in an enclosure, but consider potential glare from external light sources.
• ESD Protection: While not explicitly stated, standard ESD handling precautions for LEDs should be observed during assembly.

8. Technical Comparison & Differentiation

Compared to older technologies like standard GaAsP or GaP red LEDs, the AlInGaP technology in the LTS-4710AJD offers significantly higher luminous efficiency. This means it can achieve higher brightness at the same current, or the same brightness at much lower current. Compared to some very low-current \"super-bright\" LEDs, this device is characterized and guaranteed for segment matching at low currents, which is critical for uniform appearance in a seven-segment format. Its characterization down to 1 mA per segment is a specific design focus not always found in generic seven-segment displays.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display directly from a 3.3V or 5V microcontroller pin?

A: No. You must use a current-limiting resistor or a dedicated driver IC. A microcontroller pin cannot safely source or sink the current required for multiple segments simultaneously and lacks inherent current regulation.

Q: What is the difference between peak wavelength (656 nm) and dominant wavelength (640 nm)?

A> Peak wavelength is the point of maximum spectral power. Dominant wavelength is the single wavelength of monochromatic light that would match the perceived color. For red LEDs, the dominant wavelength is often slightly shorter (more orange) than the peak wavelength, as perceived by the human eye.

Q: The continuous current rating derates above 25°C. What is the maximum safe current at 70°C?

A> Using the derating factor of 0.33 mA/°C: Temperature increase = 70°C - 25°C = 45°C. Current derating = 45°C * 0.33 mA/°C = 14.85 mA. Maximum safe continuous current ≈ 25 mA - 14.85 mA = 10.15 mA per segment.

10. Practical Design Case

Scenario: Designing a battery-powered digital thermometer with a 4-digit display using the LTS-4710AJD, powered by a 3.3V system.

Implementation: The four digits would be multiplexed. A microcontroller would control the common anode pins (via transistor switches) and the segment cathode lines (via its GPIO pins, each with a series resistor). To conserve power, the segments are driven at 2 mA average current. Using multiplexing with a 1/4 duty cycle, the instantaneous current per segment during its active time slot would be 8 mA (2 mA / 0.25 duty cycle), which is well within the peak and continuous ratings. The forward voltage at ~8 mA is approximately 2.2V (from the typical I-V curve). The current-limiting resistor value would be R = (3.3V - 2.2V) / 0.008A = 137.5 Ω. A standard 150 Ω resistor would be used, resulting in a slightly lower instantaneous current of ~7.3 mA. This design achieves good brightness while maximizing battery life.

11. Technology Principle Introduction

The LTS-4710AJD utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material grown on a GaAs (Gallium Arsenide) substrate. AlInGaP is a direct bandgap material well-suited for emitting light in the red to yellow-orange spectrum. The specific composition of aluminum, indium, and gallium determines the bandgap energy and thus the emitted wavelength (~656 nm for this device). The \"high-efficiency\" designation refers to advanced epitaxial growth techniques that minimize crystal defects and improve the internal quantum efficiency—the percentage of electron-hole recombinations that produce photons. The non-transparent GaAs substrate absorbs emitted light, so the chip design uses techniques to maximize light extraction from the top surface, contributing to the high brightness.

12. Technology Trends

The trend in display LEDs continues toward higher efficiency and lower operating voltages. While AlInGaP is mature for red/orange/yellow, newer materials like InGaN (Indium Gallium Nitride) now dominate the blue, green, and white LED markets and are also being developed for high-performance red emitters. For seven-segment displays, the trend is towards integration—embedding the driver IC and even a microcontroller within the display package to create \"intelligent\" modules that simplify system design. Furthermore, there is a push for even lower minimum operating currents for ultra-low-power IoT and wearable devices, as well as improvements in high-temperature performance for automotive and industrial applications.