LTS-4730AJD 0.4-inch Hyper Red LED Display Datasheet - Digit Height 10.16mm - Forward Voltage 2.6V - Power 70mW - English Technical Document

1. Product Overview

The LTS-4730AJD is a compact, single-digit, seven-segment display module designed for applications requiring clear numeric readouts. Its core function is to visually represent the digits 0-9 and some letters using individually addressable LED segments. The device is engineered with AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology, specifically in a hyper red color, which offers distinct advantages in visibility and efficiency for certain lighting conditions compared to standard red LEDs.

The primary market for this component includes industrial control panels, instrumentation, test and measurement equipment, consumer appliances, and any embedded system where a simple, reliable, and low-power numeric indicator is needed. Its design prioritizes readability and longevity in various operating environments.

1.1 Core Advantages and Features

The datasheet highlights several key features that define the product's value proposition:

• Digit Height: Features a 0.4-inch (10.16 mm) character height, providing a good balance between size and readability for panel-mounted applications.
• Optical Quality: Offers continuous uniform segments, excellent character appearance, high brightness, high contrast, and a wide viewing angle. These attributes ensure the displayed number is clear and legible from various perspectives.
• Efficiency and Reliability: Designed for low power requirement and offers solid-state reliability, meaning no moving parts and high resistance to shock and vibration.
• Consistency: The luminous intensity is categorized (binned), allowing designers to select components with matched brightness levels for multi-digit displays, ensuring uniform appearance.
• Aesthetics: The device has a gray face with white segments, which enhances contrast when the LEDs are off and provides a neutral, professional appearance.

2. Technical Specifications Deep Dive

This section provides an objective analysis of the critical parameters defined in the datasheet.

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. They are not conditions for normal operation.

• Power Dissipation per Segment: 70 mW. This is the maximum power each individual LED segment can handle continuously.
• Peak Forward Current per Segment: 90 mA, but only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This is useful for multiplexing or brief overdrive for increased brightness.
• Continuous Forward Current per Segment: 25 mA at 25°C. This current derates linearly above 25°C at a rate of 0.33 mA/°C. For example, at 85°C, the maximum allowable continuous current would be approximately: 25 mA - ((85°C - 25°C) * 0.33 mA/°C) = 5.2 mA. This derating is crucial for thermal management.
• 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 temperature ranges.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This is a standard guideline for wave or reflow soldering processes.

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

These are the typical performance parameters under specified test conditions.

• Average Luminous Intensity (I_V): 200-650 µcd (microcandelas) at a forward current (I_F) of 1 mA. The wide range indicates the binning process; designers can specify a minimum intensity.
• Peak Emission Wavelength (λ_p): 650 nm (nanometers). This is the wavelength at which the LED emits the most optical power, defining its hyper red color.
• Spectral Line Half-Width (Δλ): 20 nm. This parameter describes the spectral purity or bandwidth of the emitted light. A value of 20 nm is typical for AlInGaP red LEDs.
• Dominant Wavelength (λ_d): 639 nm. This is the single wavelength perceived by the human eye, which may differ slightly from the peak wavelength.
• Forward Voltage per Segment (V_F): 2.1V (Min), 2.6V (Typ) at I_F=20 mA. This is critical for designing the current-limiting circuitry. The voltage drop across each segment must be accounted for in the power supply design.
• Reverse Current per Segment (I_R): 100 µA (Max) at V_R=5V. This is the small leakage current when the LED is reverse-biased.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (Max). This specifies the maximum allowable ratio between the brightest and dimmest segments within a single device, ensuring visual uniformity.

3. Binning System Explanation

The datasheet explicitly states that the devices are \"categorized for luminous intensity.\" This refers to a binning or sorting process post-manufacturing.

• Luminous Intensity Binning: Due to natural variations in the semiconductor manufacturing process, LEDs are tested and sorted into different bins based on their measured light output at a standard current (e.g., 1mA). The LTS-4730AJD is available with a minimum intensity of 200 µcd and a typical up to 650 µcd. For applications requiring consistent brightness across multiple digits, specifying parts from the same or adjacent intensity bins is essential.
• Wavelength/Color Binning: While not explicitly detailed with multiple codes, the specification of \"Hyper Red\" and the given dominant/peak wavelengths (639nm, 650nm) imply a tightly controlled color point. For this product, the primary binning appears focused on luminous intensity.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical / Optical Characteristic Curves.\" While the specific graphs are not provided in the text, we can infer their standard content and importance.

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph would show how light output increases with forward current. It is typically non-linear, with efficiency dropping at very high currents due to heating. The 20mA test point is a common operating condition.
• Forward Voltage vs. Forward Current: This curve shows the relationship between voltage and current for the LED junction. It is exponential in nature. The specified V_F of 2.6V at 20mA is a point on this curve.
• Relative Luminous Intensity vs. Ambient Temperature: LED light output decreases as junction temperature increases. This curve is vital for understanding performance in elevated temperature environments and aligns with the current derating specification.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at 650nm and the 20nm half-width, confirming the hyper red color characteristics.

5. Mechanical & Package Information

5.1 Package Dimensions and Drawing

The device has a standard through-hole DIP (Dual In-line Package) footprint. The dimensional drawing provides all critical measurements for PCB (Printed Circuit Board) layout, including:

• Overall height, width, and depth.
• Pin spacing (e.g., standard 0.1-inch / 2.54mm row spacing is typical).
• Digit window position and size.
• Seating plane and lead dimensions.
• Tolerances are specified as ±0.25 mm unless otherwise noted, which is standard for this type of component.

5.2 Pin Connection and Internal Circuit Diagram

The display has a common anode configuration. The internal circuit diagram shows that segments are individual LEDs. The pinout table is essential for correct wiring:

• Common Anode Pins: Pins 1 & 3 are connected together as the anode for segments G, H, and J (the right-side vertical segments and the center horizontal segment). Pin 14 is the anode for segments B, C, and the Decimal Point (D.P.).
• Cathode Pins: Pins 7 (H & J), 8 (G), 9 (D.P.), 10 (C), and 11 (B) are the cathodes for individual segments or segment pairs. To illuminate a segment, its corresponding cathode must be connected to a lower voltage (ground) while the relevant common anode is supplied with a positive voltage through a current-limiting resistor.
• No-Connection Pins: Pins 2, 4, 5, 6, 12, and 13 are marked as \"NO PIN\" or \"NO CONNECTION,\" meaning they are physically present for mechanical stability but have no electrical function.

6. Soldering and Assembly Guidelines

The key guideline provided is the soldering temperature specification: a maximum of 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This is critical to prevent thermal damage to the LED chips, the epoxy lens, and the internal wire bonds.

• Process: This parameter is suitable for both wave soldering and reflow soldering processes, though care must be taken to ensure the entire assembly profile stays within limits.
• Hand Soldering: If hand soldering is necessary, a temperature-controlled iron should be used, and contact time with the pins should be minimized.
• Storage: While not specified, standard ESD (Electrostatic Discharge) precautions should be observed. Storing components in anti-static bags in a cool, dry environment is recommended.

7. Application Suggestions

7.1 Typical Application Circuits

Driving a common anode seven-segment display like the LTS-4730AJD typically involves using a microcontroller or a dedicated display driver IC (e.g., 74HC595 shift register with current-limiting resistors, or a MAX7219). The circuit must:

1. Provide a positive voltage to the common anode pins (1/3 and 14).
2. Sink current through the individual cathode pins to ground via current-limiting resistors. The resistor value is calculated using Ohm's Law: R = (V_supply - V_F) / I_F. For a 5V supply and a target I_F of 10mA with V_F=2.6V: R = (5 - 2.6) / 0.01 = 240 Ω.

7.2 Design Considerations

• Current Limiting: Always use external current-limiting resistors for each segment or common cathode line. Relying on the microcontroller's pin current limit is not safe or reliable.
• Multiplexing: For multi-digit displays, a multiplexing technique is used where digits are illuminated one at a time rapidly. The peak current rating (90mA at 1/10 duty) allows for brief higher currents to compensate for the reduced duty cycle, maintaining perceived brightness.
• Viewing Angle: The wide viewing angle is beneficial but consider the final enclosure. The gray face provides good off-state contrast.
• Thermal Management: Adhere to the current derating curve for high-temperature environments. Ensure adequate ventilation if multiple displays are used.

8. Technical Comparison and Differentiation

The LTS-4730AJD's primary differentiators are its use of AlInGaP technology and hyper red color.

• vs. Standard GaAsP/GaP Red LEDs: AlInGaP LEDs generally offer higher efficiency, better brightness, and more stable wavelength over temperature and drive current. The hyper red (650nm) is deeper and more saturated than standard red (~630nm), which can be advantageous for certain indicators or in high-ambient-light conditions.
• vs. Larger/Smaller Displays: The 0.4-inch digit is a common size, offering a good compromise. Smaller digits save space but are harder to read at a distance; larger digits are more visible but consume more panel area and power.
• vs. Low-Efficiency Displays: The \"low power requirement\" and high brightness indicate good luminous efficacy, making it suitable for battery-powered devices or applications where heat generation is a concern.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the difference between peak wavelength (650nm) and dominant wavelength (639nm)?
A: Peak wavelength is the physical peak of the spectral output. Dominant wavelength is the single wavelength that the human eye perceives as the color, calculated from the full spectrum. Both are used to specify color, with dominant wavelength often being more relevant for visual applications.

Q: Can I drive this display directly from a 5V microcontroller pin?
A: No. You must use a current-limiting resistor in series with each segment cathode. A microcontroller pin set as an output low can sink the current, but the resistor is mandatory to set the correct current and protect both the LED and the microcontroller.

Q: The max 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, reliable operating point that provides good brightness while staying well within the 25mA absolute maximum, allowing a safety margin. You can design for 10-20mA depending on your brightness and power requirements.

Q: What does \"categorized for luminous intensity\" mean for my order?
A> It means the LEDs are sorted by brightness after production. When ordering, you may be able to specify a minimum luminous intensity bin (e.g., \"400 µcd min\") to ensure all displays in your project have similar brightness. Consult the distributor or manufacturer for available bin codes.

10. Practical Use Case Example

Scenario: Designing a simple digital voltmeter readout.
A microcontroller with an analog-to-digital converter (ADC) measures a voltage. The firmware converts this value to a decimal number. To display it on the LTS-4730AJD, the microcontroller would:

1. Use a look-up table to determine which segments (a-g, dp) need to be lit for each digit 0-9.
2. Employ a multiplexing routine if multiple digits are used. For a single digit, it would simply set the correct cathode pins low while keeping the common anode pins high via a transistor switch, with appropriate current-limiting resistors on each cathode line.
3. The hyper red color provides clear visibility. The low power consumption is beneficial if the meter is portable. The wide viewing angle allows the reading to be seen from the side.

11. Technology Principle Introduction

The LTS-4730AJD is based on AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material grown on a non-transparent GaAs (Gallium Arsenide) substrate. When a forward voltage is applied across the p-n junction of this material, electrons and holes recombine, releasing energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light. For this device, the composition is tuned to produce light in the \"hyper red\" region of the spectrum (~650nm). The non-transparent substrate helps improve contrast by absorbing stray light. Each segment of the digit is a separate LED chip or a portion of a chip, wired internally to the corresponding pins.

12. Technology Trends

While seven-segment displays remain fundamental, trends in indicator technology include:

• Integration: Movement towards displays with integrated driver ICs (I2C, SPI interface) to simplify microcontroller design and reduce component count.
• Materials: Ongoing development in LED materials like InGaN (for blue/green/white) and improved AlInGaP for higher efficiency and broader color gamuts.
• Form Factors: Increased adoption of surface-mount device (SMD) packages for automated assembly, though through-hole displays like this one remain popular for prototyping, repair, and certain industrial applications.
• Alternatives: For more complex information, OLED or TFT LCD modules are becoming more cost-competitive, but for simple, bright, low-power, and highly reliable numeric readouts, LED seven-segment displays like the LTS-4730AJD continue to be a robust and optimal solution.