LTS-4817SW-P LED Display Datasheet - 0.39-inch Digit Height - White Segments - 3.2V Forward Voltage - English Technical Document

1. Product Overview

The LTS-4817SW-P is a surface-mount, single-digit alphanumeric LED display module. It is designed with a 0.39-inch (10.0 mm) digit height, making it suitable for applications requiring compact, highly legible numeric or limited alphanumeric indication. The device utilizes InGaN (Indium Gallium Nitride) semiconductor technology to produce white light, offering a modern alternative to traditional filtered or phosphor-converted white LEDs. Its gray face with white segments provides excellent contrast for optimal readability.

1.1 Key Features and Positioning

This display is engineered for reliability and performance in consumer electronics, industrial instrumentation, automotive dashboards, and appliance control panels. Its core advantages include a continuous, uniform segment design that eliminates gaps for a clean appearance, and a wide viewing angle ensuring visibility from various positions. The device is categorized for luminous intensity and forward voltage, allowing for tighter brightness and color consistency in batch production. Being a lead-free package compliant with RoHS directives makes it suitable for global markets with strict environmental regulations.

2. Technical Specifications Deep Dive

The performance of the LTS-4817SW-P is defined by a comprehensive set of electrical and optical parameters critical for design-in.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage may occur. The maximum power dissipation per segment is 35 mW. The peak forward current is 50 mA, but only under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width). The continuous forward current per segment is derated from 10 mA at 25°C at a rate of 0.11 mA/°C, meaning the allowable current decreases as ambient temperature increases. The operating and storage temperature range is specified from -35°C to +105°C, indicating robustness for harsh environments. The soldering condition is specified as 260°C for 3 seconds at 1/16 inch (approximately 1.6 mm) below the seating plane.

2.2 Electrical & Optical Characteristics

Under typical test conditions (Ta=25°C, IF=5mA), the key parameters are: The average luminous intensity per chip ranges from a minimum of 71 mcd to a maximum of 165 mcd. The forward voltage per chip (VF) ranges from 2.7V to 3.2V. The reverse current (IR) is a maximum of 100 µA at VR=5V, but this is a test condition only; the device is not intended for continuous reverse bias operation. The luminous intensity matching ratio between segments is 2:1 or better, ensuring uniform brightness. Chromaticity coordinates (x, y) are provided per the 1931 CIE standard, with typical values around x=0.294, y=0.286, defining the white point. A crosstalk specification of ≤ 2.5% is noted, which refers to undesired light leakage between adjacent segments.

3. Binning System Explanation

To ensure consistency, the LEDs used in this display are sorted into bins based on key parameters.

3.1 Forward Voltage (VF) Binning

LEDs are grouped into bins (3, 4, 5, 6, 7) based on their forward voltage at 5mA. Each bin has a 0.1V range (e.g., Bin 3: 2.70-2.80V, Bin 4: 2.80-2.90V). A tolerance of ±0.1V is allowed within each bin. This allows designers to select parts for applications sensitive to voltage drop or power supply design.

3.2 Luminous Intensity (IV) Binning

Brightness is categorized into bins labeled Q11, Q12, Q21, Q22, R11, R12, R21. Each bin covers a specific mcd range at 5mA (e.g., Q11: 71.0-81.0 mcd, R21: 146.0-165.0 mcd). A tolerance of ±15% applies to each bin. This system enables matching display brightness across multiple units or digits.

3.3 Hue (Chromaticity) Binning

The color of the white light is controlled through hue bins (S1-2, S2-2, S3-1, S3-2, S4-1, S4-2, S5-1, S6-1). Each bin is defined by a quadrilateral area on the CIE 1931 chromaticity diagram, specifying the allowable range of x and y coordinates. A tolerance of ±0.01 is maintained. This minimizes visible color differences between segments or displays.

4. Performance Curve Analysis

While specific graphical data is referenced in the document, typical curves for such devices include the relationship between forward current (IF) and forward voltage (VF), which is exponential. The relationship between forward current (IF) and luminous intensity (IV) is generally linear within the operating range. The effect of ambient temperature (Ta) on luminous intensity shows a negative coefficient; brightness decreases as temperature increases. Understanding these curves is vital for driving circuit design and thermal management to maintain consistent optical output over the product's lifetime.

5. Mechanical & Package Information

5.1 Package Dimensions

The device conforms to a specific SMD footprint. Critical dimensions include the overall length, width, and height, as well as the lead (pin) spacing and size. Tolerances are typically ±0.25 mm unless otherwise specified. Additional quality notes address limits for foreign material, ink contamination, bubbles in the segment, bending of the reflector, and pin burrs, which are crucial for assembly yield and final appearance.

5.2 Pinout and Circuit Diagram

The display has a common anode configuration. The internal circuit diagram shows ten pins: two are common anode pins (pins 3 and 8), and the remaining eight are cathodes for segments A, B, C, D, E, F, G, and the decimal point (DP). Pin 1 is listed as \"No Connection.\" This configuration requires a current-sinking driver; the anodes are connected to a positive supply (through current-limiting resistors), and individual segments are illuminated by pulling their corresponding cathode pins to ground.

5.3 Recommended Soldering Pattern

A land pattern (footprint) for PCB design is provided. This pattern ensures proper solder joint formation during reflow, provides adequate mechanical strength, and prevents solder bridging. Adherence to this pattern is critical for reliable surface-mount assembly.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Parameters

The device can withstand a maximum of two reflow cycles, with a cooling period to room temperature required between cycles. The recommended reflow profile has a pre-heat zone of 120-150°C for a maximum of 120 seconds, and a peak temperature not exceeding 260°C. For manual repair, soldering iron temperature should not exceed 300°C, with contact time limited to 3 seconds maximum. Exceeding these conditions may damage the plastic package or the LED chips.

6.2 Electrostatic Discharge (ESD) Precautions

The InGaN chip is sensitive to electrostatic discharge. Mandatory precautions include the use of grounded wrist straps or anti-static gloves by personnel. All workstations, equipment, and storage facilities must be properly grounded. The use of ionizers is recommended to neutralize static charge that may accumulate on the plastic package during handling. Failure to observe ESD controls can lead to latent or catastrophic device failure.

7. Packaging & Ordering Information

7.1 Tape and Reel Packaging

The components are supplied in embossed carrier tape wound onto reels, suitable for automated pick-and-place machines. Detailed reel dimensions (reel diameter, hub width, etc.) and carrier tape dimensions (pocket size, pitch, sprocket hole details) are specified. Key tolerances include a ±0.20 mm cumulative tolerance over 10 sprocket holes and a camber (warp) limit of 1 mm over 250 mm of carrier tape.

8. Application Notes & Design Considerations

8.1 Typical Application Circuits

A typical drive circuit involves connecting the common anode pins to a positive voltage source (e.g., 5V) via a current-limiting resistor. The value of this resistor is calculated based on the supply voltage, the forward voltage of the LED segment (VF), and the desired forward current (IF). For multiplexing multiple digits, a transistor or dedicated driver IC can be used to switch the common anodes, while the segment cathodes are driven by a shift register or port expander.

8.2 Brightness and Current Control

Since luminous intensity is approximately proportional to forward current, brightness can be controlled via PWM (Pulse Width Modulation) of the drive current. This is more effective and efficient than analog dimming via variable voltage. The derating curve for continuous current must be respected in high-temperature applications to prevent overheating and accelerated lumen depreciation.

8.3 Thermal Management

Although power dissipation is low per segment, the combined heat from multiple illuminated segments in a small package must be considered. Adequate PCB copper area around the pads can act as a heat sink. Ensuring good airflow in the end-product enclosure helps maintain the junction temperature within safe limits, preserving longevity and color stability.

9. Technical Comparison & Differentiation

Compared to older technologies like filtered GaP or GaAsP LEDs, the InGaN white LED offers higher brightness, better efficiency, and a more modern white color point. The common anode configuration is common and supported by many standard driver ICs. The 0.39-inch size fills a niche between smaller indicators and larger multi-digit displays. The detailed binning for intensity, voltage, and hue provides a level of consistency that is essential for professional-grade products where visual uniformity is critical.

10. Frequently Asked Questions (FAQ)

10.1 What is the purpose of the two common anode pins?

The two pins (3 and 8) are internally connected. Providing two pins helps distribute the total anode current, reduces current density in the package leads, and can aid in PCB layout for symmetry and reliability.

10.2 Can I drive this display with a 3.3V microcontroller?

Yes, but careful design is needed. The typical VF is 2.7-3.2V. At 3.3V supply, the voltage headroom for the current-limiting resistor is very small (0.1-0.6V). This requires a very small resistor value, making the current sensitive to variations in VF and supply voltage. A 5V supply is generally recommended for more stable operation, or a dedicated constant-current LED driver should be used.

10.3 How do I interpret the hue bin codes (e.g., S3-2)?

The bin code corresponds to a specific region on the CIE chromaticity diagram defined in the datasheet. Designers can specify a required bin or range of bins when ordering to ensure color matching across a production run. For most general applications, any standard white bin is acceptable.

11. Practical Design Case Study

Consider designing a digital timer display using four LTS-4817SW-P digits. The design would involve creating a PCB with four identical footprints according to the recommended soldering pattern. A microcontroller would multiplex the digits, energizing one digit's common anode at a time while outputting the segment pattern for that digit. Current-limiting resistors would be placed on the common anode lines. The refresh rate must be high enough (typically >60 Hz) to avoid visible flicker. The bin codes for intensity and hue should be specified to the supplier to ensure all four digits look identical. ESD protection during assembly and handling is mandatory.

12. Technology Principle

The LTS-4817SW-P uses InGaN-based LED chips. InGaN is a semiconductor material capable of emitting light in the blue to ultraviolet spectrum. To produce white light, the device likely employs a blue-emitting InGaN chip combined with a phosphor coating. The phosphor absorbs a portion of the blue light and re-emits it as yellow light. The mixture of the remaining blue light and the emitted yellow light is perceived by the human eye as white. This is a common and efficient method for creating white LEDs.

13. Industry Trends

The trend in SMD displays and indicators continues towards higher efficiency (more lumens per watt), allowing for lower power consumption or higher brightness. There is also a drive towards miniaturization while maintaining or improving legibility. Color consistency and tighter binning are increasingly important for high-end consumer electronics. Furthermore, the integration of driver circuitry directly with the display package is a growing trend, simplifying system design for end-users.