LTS-5703AJS 0.56-inch Yellow LED Display Datasheet - Digit Height 14.22mm - Forward Voltage 2.6V - Power 40mW - English Technical Document

1. Product Overview

The LTS-5703AJS is a high-performance, low-power seven-segment LED display module. Its primary function is to provide clear, bright numeric and limited alphanumeric character output in electronic devices. The core application is in instrumentation, consumer electronics, and industrial control panels where reliable, low-current digital readouts are required.

The device is positioned as a solution offering excellent readability and energy efficiency. Its core advantages stem from the use of advanced AlInGaP semiconductor material, which provides high brightness and good color purity at relatively low drive currents compared to older technologies.

1.1 Core Advantages and Target Market

The key features that define this product's market position include a 0.56-inch (14.22 mm) digit height, which offers a good balance between size and visibility. The segments are continuous and uniform, ensuring a pleasing aesthetic character appearance. The device requires low power, making it suitable for battery-operated or energy-conscious applications. It delivers high brightness and high contrast, coupled with a wide viewing angle, ensuring legibility from various positions. The solid-state construction offers inherent reliability. Finally, the devices are categorized for luminous intensity, allowing for consistent brightness matching in multi-digit displays.

The target market includes designers of portable test equipment, digital multimeters, clock radios, appliance control panels, and any embedded system requiring a simple, direct-drive numeric display.

2. Technical Specifications Deep Dive

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

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's function. The device utilizes AlInGaP (Aluminum Indium Gallium Phosphide) yellow LED chips. These are fabricated on a non-transparent GaAs substrate, which helps in directing light forward and can improve contrast. The package has a light gray face with white segments, a combination designed to enhance contrast when the segments are unlit.

• Average Luminous Intensity (I_V): Ranges from a minimum of 320 \u00b5cd to a typical 700 \u00b5cd at a forward current (I_F) of just 1mA. This exceptionally low drive current for such brightness is a key specification, enabling very low system power consumption.
• Peak Emission Wavelength (\u03bb_p): Typically 588 nm, placing it in the yellow region of the visible spectrum.
• Spectral Line Half-Width (\u0394\u03bb): Typically 15 nm, indicating a relatively narrow spectral bandwidth, which contributes to a pure yellow color.
• Dominant Wavelength (\u03bb_d): Typically 587 nm, closely matching the peak wavelength.
• Luminous Intensity Matching Ratio: Specified as 2:1 maximum under similar light area conditions at I_F=1mA. This means the brightness of different segments in one device, or between devices, will not vary by more than a factor of two, ensuring uniform appearance.

It is important to note that luminous intensity is measured using a sensor and filter that approximate the CIE photopic eye-response curve, ensuring the values correlate with human visual perception.

2.2 Electrical Parameters

The electrical characteristics define the interface between the display and the driving circuitry.

• Forward Voltage per Segment (V_F): Typically 2.6V with a maximum of 2.6V at I_F=20mA. The minimum is 2.05V. Designers must ensure the driving circuit can provide at least 2.6V to achieve the rated brightness at 20mA.
• Reverse Current per Segment (I_R): Maximum 100 \u00b5A at a Reverse Voltage (V_R) of 5V. This parameter is important for circuit protection; exceeding the reverse voltage rating can damage the LED.
• Continuous Forward Current per Segment: The absolute maximum rating is 25 mA. However, a derating factor of 0.33 mA/\u00b0C applies linearly from 25\u00b0C. This means at higher ambient temperatures, the maximum allowable continuous current must be reduced to prevent overheating and premature failure.
• Peak Forward Current: Can be pulsed up to 60 mA under specific conditions (1/10 duty cycle, 0.1ms pulse width). This allows for multiplexing schemes or brief over-driving for increased brightness.
• Power Dissipation per Segment: Absolute maximum is 40 mW. This thermal limit, combined with the current derating, is critical for reliability.

2.3 Thermal and Environmental Ratings

The device's operational limits are defined by temperature ranges.

• Operating Temperature Range: -35\u00b0C to +105\u00b0C. This wide range makes it suitable for use in various environments, from industrial cold storage to hot equipment enclosures.
• Storage Temperature Range: -35\u00b0C to +105\u00b0C.
• Solder Condition: Specifies that during assembly, the device body temperature must not exceed the maximum temperature rating. The guideline is soldering at 260\u00b0C for 3 seconds with the solder point at least 1/16 inch (approx. 1.6mm) below the seating plane of the package.

3. Binning System Explanation

The datasheet indicates the devices are \"categorized for luminous intensity.\" This refers to a binning process. While specific bin codes are not provided in this document, typical categorization for such displays involves sorting manufactured units based on measured luminous intensity at a standard test current (e.g., 1mA or 20mA).

Units are grouped into bins with defined minimum and maximum intensity values. This allows customers to select bins for their application, ensuring consistency in brightness across all digits in a multi-digit display. For example, a designer might specify all displays must come from a bin with I_V between 500 \u00b5cd and 600 \u00b5cd at 1mA. The 2:1 intensity matching ratio specified is the worst-case variation allowed within a single device or potentially within a standard bin.

4. Performance Curve Analysis

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

4.1 Forward Current vs. Forward Voltage (I-V Curve)

This fundamental curve shows the relationship between the current flowing through an LED segment and the voltage across it. It is non-linear. The typical V_F of 2.6V at 20mA is a point on this curve. The curve helps designers size current-limiting resistors correctly and understand the voltage requirements of the driving circuit, especially under multiplexing where average current differs from instantaneous current.

4.2 Luminous Intensity vs. Forward Current

This graph is crucial for brightness control. It shows how light output increases with current. It is typically linear over a range but will saturate at very high currents. The ability to drive segments at as low as 1mA is a key feature, and this curve would show the relative brightness at that point compared to the typical 20mA drive.

4.3 Luminous Intensity vs. Ambient Temperature

LED light output decreases as junction temperature increases. This curve quantifies that derating. It is essential for applications operating at high ambient temperatures to ensure the display remains sufficiently bright over the entire operating range.

4.4 Spectral Distribution

A graph showing the relative light intensity across wavelengths, centered around the 588 nm peak with the 15 nm half-width. This defines the exact shade of yellow.

5. Mechanical and Package Information

5.1 Package Dimensions and Drawing

The device has a standard 10-pin single-digit seven-segment display footprint. The datasheet includes a detailed dimensioned drawing. Key notes specify that all dimensions are in millimeters, with standard tolerances of \u00b10.25 mm unless stated otherwise. A specific note mentions a pin tip shift tolerance of +0.4 mm, which is important for PCB hole placement and wave soldering processes.

5.2 Pin Connection and Polarity Identification

The device uses a common cathode configuration. This means all the cathodes (negative terminals) of the individual LED segments are connected together internally. There are two common cathode pins (pins 3 and 8), which are internally connected. This dual-pin design helps in current distribution and PCB layout. The anodes (positive terminals) for each segment (A, B, C, D, E, F, G, and the Decimal Point) are on separate pins. The specific pinout is: 1:E, 2:D, 3:Common Cathode, 4:C, 5:D.P., 6:B, 7:A, 8:Common Cathode, 9:F, 10:G.

5.3 Internal Circuit Diagram

The provided diagram visually confirms the common cathode architecture, showing all segment LEDs with their anodes on individual pins and their cathodes tied together to pins 3 and 8.

6. Soldering and Assembly Guidelines

The absolute maximum ratings section provides critical assembly data. The specified solder condition is industry-standard for through-hole components: a maximum soldering iron temperature of 260\u00b0C for a duration not exceeding 3 seconds, with the solder joint located at least 1.6mm below the package body to minimize heat transfer to the LED chips and internal bonds. During any assembly process involving heat (like wave soldering or manual repair), the temperature of the display unit itself must not exceed its maximum storage temperature rating. Proper handling to avoid electrostatic discharge (ESD) is also a standard, though not explicitly stated, precaution for LED devices.

7. Application Suggestions

7.1 Typical Application Circuits

For a common cathode display, the driving circuit typically connects the common cathode pins to ground. Each segment anode pin is connected to a positive voltage supply (V_CC) through a current-limiting resistor. The resistor value is calculated using R = (V_CC - V_F) / I_F. For example, with a 5V supply, a V_F of 2.6V, and a desired I_F of 10mA, the resistor would be (5 - 2.6) / 0.01 = 240 Ohms. The display can be driven directly by microcontroller I/O pins if they can source the required current (e.g., 10-20mA per segment), often requiring external driver transistors or dedicated LED driver ICs for multiplexing multiple digits.

7.2 Design Considerations and Notes

• Current Limiting: Always use series resistors. Never connect an LED directly to a voltage source.
• Multiplexing: To drive multiple digits, a multiplexing scheme is used where digits are illuminated one at a time rapidly. The peak current can be higher (up to the 60mA rating) to compensate for the lower duty cycle, maintaining perceived brightness.
• Viewing Angle: The wide viewing angle is beneficial but consider the intended user's position when mounting the display.
• Brightness Matching: For multi-digit displays, use devices from the same luminous intensity bin or implement software brightness calibration using PWM if variation is noticeable.
• Low Power Design: Leverage the 1mA drive capability for battery-sensitive applications. The brightness at 1mA (min 320 \u00b5cd) is often sufficient for indoor use.

8. Technical Comparison and Differentiation

The LTS-5703AJS differentiates itself primarily through its AlInGaP technology and very low current operation. Compared to older red GaAsP or GaP LEDs, AlInGaP offers higher efficiency, leading to greater brightness at the same current or equivalent brightness at much lower current. Compared to contemporary high-brightness red LEDs, the yellow color may offer better visibility or lower eye strain in certain applications. Its low V_F (compared to blue or white LEDs) is also an advantage in low-voltage systems. The categorization for intensity provides an advantage in applications requiring uniformity over simple, unbinned commodity displays.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display with 3.3V logic?
A: Yes. The typical V_F is 2.6V, so a 3.3V supply provides enough headroom. Calculate the series resistor accordingly: e.g., for 10mA, R = (3.3 - 2.6) / 0.01 = 70 Ohms.

Q: What is the purpose of having two common cathode pins?
A: They are internally connected. Having two pins helps distribute the total cathode current (which is the sum of all illuminated segment currents) across two PCB traces and solder joints, improving reliability and potentially reducing voltage drop.

Q: The specs show a max continuous current of 25mA but a test condition of 20mA for V_F. Which should I use for design?
A: The 20mA figure is the standard test condition for reporting typical characteristics like V_F and wavelength. For reliable long-term operation, it is prudent to design for a continuous current at or below 20mA, especially if the ambient temperature is expected to be above 25\u00b0C, respecting the derating curve.

Q: How do I achieve the same brightness if I multiplex 4 digits?
A: With a 1/4 duty cycle, you need to multiply the instantaneous segment current by 4 to achieve the same average current and thus similar perceived brightness. If you want an average of 5mA per segment, you would pulse each segment at 20mA. Ensure this pulsed current (20mA) and the resulting instantaneous power dissipation are within the absolute maximum ratings (60mA peak, 40mW).

10. Practical Use Case Example

Design Case: A 4-Digit Portable Digital Thermometer.
The design goal is long battery life and clear readability. The microcontroller has limited I/O and power budget.
Implementation: Use four LTS-5703AJS displays in a multiplexed configuration. Connect all corresponding segment anodes (A, B, C...) together across the four digits. Each digit's common cathode is controlled by a separate NPN transistor driven by a microcontroller pin. The microcontroller cycles through turning on one digit's cathode at a time while outputting the segment pattern for that digit on the common anode lines. To save power, the drive current is set to 5mA average. Using multiplexing with a 1/4 duty cycle, the instantaneous current per segment is set to 20mA (5mA * 4). This is within the 60mA peak rating. The perceived brightness will be good, and the average power consumption per segment is very low, extending battery life significantly compared to using displays that require 10-20mA continuous current per segment.

11. Technology Principle Introduction

The LTS-5703AJS is based on AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material grown on a GaAs (Gallium Arsenide) substrate. In an LED, when a forward voltage is applied across the p-n junction, 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 defines the wavelength (color) of the emitted light. The yellow emission (~587-588 nm) is achieved with a specific ratio of aluminum, indium, and gallium. The non-transparent GaAs substrate absorbs stray light, improving contrast by preventing internal reflection that could illuminate unlit segments. The common cathode configuration simplifies driving circuitry by allowing a single switch (e.g., a transistor) to control the entire digit's on/off state during multiplexing.

12. Technology Trends and Context

While seven-segment LED displays remain vital for specific applications, the broader trend in display technology has shifted towards dot-matrix formats (for alphanumerics and graphics) and integrated controller-based modules (like OLED or TFT). However, the niche for simple, rugged, low-cost, low-power, high-brightness, and direct-drive numeric displays persists. The evolution within this niche focuses on materials science (like AlInGaP replacing older materials for better efficiency), lower operating voltages and currents, improved packaging for higher reliability and wider temperature ranges, and surface-mount versions for automated assembly. The LTS-5703AJS represents a mature point in this evolution, offering a balance of performance and practicality for its intended uses. Future developments might integrate current-limiting resistors or simple logic internally, but for many straightforward applications, the simplicity of the basic component remains a key advantage.