LTS-4812CKS-PM LED Display Datasheet - 0.39-inch Digit Height - Yellow - 2.05V Typ - English Technical Document

1. Product Overview

The LTS-4812CKS-PM is a surface-mount device (SMD) designed as a single-digit numeric display. It utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology grown on a GaAs substrate to produce yellow light emission. The display features a gray face with white segments, providing high contrast for clear character visibility. Its primary application is in electronic devices requiring compact, reliable, and bright numeric readouts, such as instrumentation panels, consumer electronics, and industrial controls.

1.1 Key Features and Advantages

• Compact Size: Features a standard digit height of 0.39 inches (10.0 mm), making it suitable for space-constrained applications.
• Optical Quality: Offers continuous uniform segments, excellent character appearance, high brightness, and a wide viewing angle for optimal readability from various positions.
• Energy Efficiency: Designed with a low power requirement, contributing to overall system energy savings.
• High Reliability: Benefits from solid-state construction, ensuring long operational life and resistance to shock and vibration.
• Standardized Output: Devices are categorized (binned) for luminous intensity and dominant wavelength, allowing for consistent performance in batch production.
• Environmental Compliance: The package is lead-free and conforms to RoHS (Restriction of Hazardous Substances) directives.

2. Technical Specifications Deep Dive

2.1 Absolute Maximum Ratings

The following limits must not be exceeded under any conditions to prevent permanent damage to the device. All values are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation per Segment: 70 mW maximum.
• Peak Forward Current per Segment: 90 mA (under pulsed conditions: 1/10 duty cycle, 0.1 ms pulse width).
• Continuous Forward Current per Segment: 25 mA. This rating derates linearly at 0.28 mA/°C for temperatures above 25°C.
• Operating & Storage Temperature Range: -35°C to +105°C.
• Soldering Temperature: Withstands iron soldering at 260°C for 3 seconds, measured 1/16 inch below the seating plane.

2.2 Electrical & Optical Characteristics

Typical performance parameters are measured at Ta=25°C. These define the standard operating behavior of the display.

• Average Luminous Intensity (Iv): Ranges from 1301 to 5400 µcd at a forward current (IF) of 1 mA. At IF=10 mA, a typical intensity of 30250 µcd is achieved.
• Forward Voltage per Chip (VF): Typically 2.05V, with a range from 1.6V (MIN) to 2.6V (MAX) at IF=20 mA.
• Peak Emission Wavelength (λp): 588 nm at IF=20 mA.
• Dominant Wavelength (λd): Ranges from 582.1 nm to 590 nm at IF=20 mA.
• Spectral Line Half-Width (Δλ): 15 nm at IF=20 mA.
• Reverse Current per Segment (IR): Maximum of 100 µA at a reverse voltage (VR) of 5V. Note: This is a test condition; the device is not intended for continuous reverse bias operation.
• Luminous Intensity Matching Ratio: The ratio between the brightest and dimmest segments in a similar light area is 2:1 maximum at IF=1 mA, ensuring uniform appearance.
• Cross Talk: Specified to be ≤ 2.5%, minimizing unwanted illumination of adjacent segments.

3. Binning System Explanation

To ensure color and brightness consistency in production, devices are sorted into bins based on measured parameters.

3.1 Luminous Intensity Bin Range

Devices are categorized into three bins (J, K, L) based on their luminous intensity measured at 1 mA. The tolerance for bin assignment is ±15%.

• Bin J: 1301 – 2100 µcd
• Bin K: 2101 – 3400 µcd
• Bin L: 3401 – 5400 µcd

3.2 Hue (Dominant Wavelength) Range

Devices are also binned into four hue groups (0, 1, 2, 3) based on their dominant wavelength, with a tolerance of ±1 nm.

• Hue 0: 582.1 – 584.0 nm
• Hue 1: 584.1 – 586.0 nm
• Hue 2: 586.1 – 588.0 nm
• Hue 3: 588.1 – 590.0 nm

Specifying bins allows designers to select parts with tightly controlled optical properties for applications requiring color or brightness uniformity across multiple displays.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet, they typically illustrate the following relationships critical for design:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the non-linear relationship, essential for calculating current-limiting resistor values and power dissipation.
• Luminous Intensity vs. Forward Current: Demonstrates how light output increases with current, aiding in brightness optimization and efficiency calculations.
• Luminous Intensity vs. Ambient Temperature: Illustrates the decrease in light output as temperature rises, which is vital for designing systems that operate in elevated temperature environments.
• Spectral Distribution: Depicts the relative power emitted across wavelengths, centered around the peak wavelength of 588 nm for this yellow LED.

5. Mechanical & Package Information

5.1 Package Dimensions

The device conforms to a standard SMD outline. Key dimensional notes include:

• All dimensions are in millimeters (mm).
• Standard tolerance is ±0.25 mm unless otherwise specified.
• Specific quality criteria are defined for foreign material, ink contamination, bubbles within segments, bending of the reflector, and plastic pin burrs to ensure consistent manufacturability and appearance.

5.2 Pin Configuration and Circuit Diagram

The display has a 10-pin configuration and uses a common anode circuit topology. The internal diagram shows the anode connections shared for segments, while each segment (A-G and DP) has its own cathode pin. This configuration is common for multiplexing multiple digits. The pinout is as follows: Pin 3 and Pin 8 are Common Anodes. Pins 1, 2, 4, 5, 6, 7, 9, 10 are cathodes for segments E, D, C, DP, B, A, F, G respectively.

5.3 Recommended Soldering Pad Pattern

A land pattern design is provided to ensure reliable solder joint formation during reflow processes. Adhering to this pattern helps prevent tombstoning, misalignment, and insufficient solder joints.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Instructions

The device is suitable for reflow soldering with the following critical constraints:

• Maximum Reflow Cycles: The component shall undergo reflow soldering no more than two times.
• Cooling Requirement: The device must be allowed to cool to normal ambient temperature between the first and second soldering process.
• Profile: A recommended thermal profile includes a pre-heat stage at 120–150°C for a maximum of 120 seconds, with a peak temperature not exceeding 260°C.

6.2 Hand Soldering

If hand soldering is necessary, it should be limited to one-time only with an iron temperature not exceeding 300°C and a soldering time of 3 seconds maximum per joint.

7. Packaging and Handling

7.1 Tape and Reel Specifications

The components are supplied in embossed carrier tape on reels for automated assembly. Key specifications include:

• Carrier tape material is black conductive polystyrene alloy.
• Dimensions comply with EIA-481-D standards.
• Packing length is 44.5 meters per 22-inch reel.
• Component quantity is 800 pieces per 13-inch reel.
• A minimum packing quantity of 200 pieces is defined for remainder lots.
• The reel includes leader and trailer parts for machine feeding.

7.2 Moisture Sensitivity and Storage

As a surface-mount device, it is sensitive to moisture absorption.

• Shipping: Devices are shipped in moisture-proof packaging.
• Storage: Unopened bags should be stored at ≤30°C and ≤60% Relative Humidity.
• Baking: If the bag is opened or parts are exposed to humid environments (>60% RH) for an extended period, baking is required before reflow to prevent popcorning or delamination. Recommended baking conditions are: 60°C for ≥48 hours for parts in reel, or 100°C for ≥4 hours / 125°C for ≥2 hours for parts in bulk.

8. Application Notes and Design Considerations

8.1 Typical Application Circuits

When designing a drive circuit for this common-anode display, a current-limiting resistor must be connected in series with each cathode pin (segment). The resistor value is calculated using the formula R = (Vcc - VF) / IF, where Vcc is the supply voltage, VF is the forward voltage of the LED (typically 2.05V), and IF is the desired forward current. For multiplexed applications driving multiple digits, appropriate switching transistors or driver ICs are needed on the anode side.

8.2 Brightness and Current Selection

The luminous intensity is highly dependent on forward current. Designers can refer to the characteristic curve of Iv vs. IF to select an operating current that meets the required brightness while staying within the absolute maximum ratings for continuous current and power dissipation. Derating the current at high ambient temperatures is crucial for reliability.

8.3 Thermal Management

Although power dissipation is low per segment, the total power for the digit and the density on the PCB should be considered. Ensuring adequate PCB copper area for the LED pads can help dissipate heat, especially when operating at higher currents or in high-temperature environments.

9. Frequently Asked Questions (FAQ)

9.1 What is the difference between Peak Wavelength and Dominant Wavelength?

Peak wavelength (λp) is the wavelength at which the emitted optical power is maximum (588 nm for this device). Dominant wavelength (λd) is the single wavelength of monochromatic light that matches the perceived color of the LED light, and it is the parameter used for hue binning (582.1-590 nm).

9.2 Can I drive this display without current-limiting resistors?

No. LEDs are current-driven devices. Operating them directly from a voltage source without a current limit will cause excessive current to flow, potentially exceeding the absolute maximum rating and destroying the LED segments. Always use series resistors or a constant-current driver.

9.3 Why is the number of reflow cycles limited to two?

The limitation is due to the thermal stress on the package materials, internal wire bonds, and the LED die itself. Multiple high-temperature cycles can degrade materials, increase the risk of delamination, or weaken solder joints, affecting long-term reliability.

9.4 How do I interpret the bin codes (e.g., J, K, L) when ordering?

The bin code specifies the guaranteed range of luminous intensity. For consistent brightness across all digits in your product, you should specify the required bin (e.g., Bin L for highest brightness) in your purchase order. The manufacturer will supply parts from that specific bin.

10. Technology and Principle Introduction

The LTS-4812CKS-PM is based on AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material grown on a GaAs (Gallium Arsenide) substrate. This material system is highly efficient for producing light in the yellow, orange, and red regions of the spectrum. When a forward voltage is applied across the p-n junction, electrons and holes recombine, releasing energy in the form of photons. The specific composition of the AlInGaP layers determines the bandgap energy and thus the wavelength (color) of the emitted light. The SMD package houses the LED chip, wire bonds, and a molded epoxy lens that shapes the light output and provides environmental protection.