LTS-4301SW LED Display Datasheet - 0.4-inch Digit Height - White Segments - Black Face - Common Cathode - English Technical Document

1. Product Overview

The LTS-4301SW is a single-digit, seven-segment alphanumeric display module designed for applications requiring clear, bright numeric readouts. Its primary function is to visually represent the digits 0-9 and some letters by selectively illuminating its seven individual LED segments (labeled A through G) and an optional decimal point (D.P.). The device is constructed using InGaN (Indium Gallium Nitride) white LED chips, which are mounted behind a segmented mask to form the character elements. The display features a black face, which provides a high-contrast background for the illuminated white segments, significantly enhancing readability under various lighting conditions. This combination is particularly effective in applications where legibility from a distance or in ambient light is critical.

The core advantages of this display include its excellent character appearance, achieved through continuous uniform segments that create a cohesive digit shape. It offers high brightness output, with typical luminous intensities reaching up to 28,000 mcd per chip under standard test conditions, ensuring visibility even in brightly lit environments. The wide viewing angle of 130 degrees (2\u03c6_1/2) allows for clear readability from off-axis positions, making it suitable for panel meters, instrumentation, consumer appliances, and industrial control panels where the viewing angle may not be directly head-on. Furthermore, its low power requirement per segment contributes to energy-efficient designs.

1.1 Technical Parameters Deep Objective Interpretation

1.1.1 Photometric and Optical Characteristics

The key photometric parameter is the Average Luminous Intensity (I_V). For the white InGaN chips used, the typical value is 28,000 millicandelas (mcd) when driven at a forward current (I_F) of 10 mA. The minimum specified value is 13,700 mcd. This parameter is measured using a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring the reported brightness correlates with human visual perception. The wide 130-degree viewing angle is defined as the full angle at which the luminous intensity drops to half of its peak value (on-axis). This specification is crucial for determining the effective viewing cone for the end-user.

The chromaticity coordinates are given as x=0.294 and y=0.286 (measured at I_F=5mA). These coordinates on the CIE 1931 chromaticity diagram define the white point of the emitted light. The provided values suggest a cool white color temperature. Luminous Intensity Matching Ratio for similar light areas is specified as 2:1 maximum. This means the brightness difference between the dimmest and brightest segment/chip under identical drive conditions should not exceed a factor of two, ensuring uniform appearance of the illuminated digit.

1.1.2 Electrical Parameters

The Forward Voltage (V_F) per LED chip typically measures 3.15V, with a range from 2.70V to 3.15V at a test current of 5 mA. Designers must account for this voltage drop when designing the driving circuitry. The Reverse Current (I_R) is specified at a maximum of 10 \u00b5A when a reverse bias of 5V is applied, indicating the leakage characteristic of the LED junction.

The Absolute Maximum Ratings define the operational limits. The Continuous Forward Current per segment is 20 mA at 25\u00b0C, with a derating factor of 0.25 mA/\u00b0C. This means the permissible continuous current decreases linearly as the ambient temperature (T_a) rises above 25\u00b0C to prevent thermal damage. For example, at 85\u00b0C, the maximum continuous current would be 20 mA - ((85-25) * 0.25 mA) = 5 mA. The Peak Forward Current, applicable for pulsed operation (1 kHz, 10% duty cycle), is 60 mA. The maximum Power Dissipation per segment is 115 mW.

1.1.3 Thermal and Environmental Specifications

The device is rated for an Operating Temperature Range of -35\u00b0C to +105\u00b0C. The Storage Temperature Range is identical. These wide ranges indicate robustness for use in environments subject to significant temperature variations. The soldering condition is specified as 260\u00b0C for 3 seconds, measured 1/16 inch (approximately 1.6 mm) below the seating plane of the component. Adherence to this profile is critical during PCB assembly to prevent damage to the LED chips or the plastic package from excessive heat.

1.2 Mechanical and Packaging Information

The display has a digit height of 0.4 inches (10.0 mm). The package dimensions are provided in millimeters. Key mechanical notes include: all dimensional tolerances are \u00b10.25 mm unless otherwise specified, and the pin tip shift tolerance is +0.4 mm, which refers to the allowable misalignment of the pin ends. The device uses a common cathode configuration. This means all the cathodes (negative terminals) of the individual segment LEDs are connected internally to one or two common pins (pins 3 and 8), while each segment anode (positive terminal) has its own dedicated pin. This configuration typically simplifies multiplexing in multi-digit displays and can influence driver IC selection.

1.2.1 Pin Connection and Internal Circuit

The pinout is as follows: Pin 1: Anode G, Pin 2: Anode F, Pin 3: Common Cathode, Pin 4: Anode E, Pin 5: Anode D, Pin 6: Anode D.P. (Decimal Point), Pin 7: Anode C, Pin 8: Common Cathode, Pin 9: Anode B, Pin 10: Anode A. Note that there are two common cathode pins (3 and 8), which are internally connected. This dual-pin design helps in distributing current and can improve reliability. The internal circuit diagram shows each of the eight LEDs (seven segments plus the decimal point) with its anode connected to the respective pin and all cathodes tied together to the common cathode pins.

1.3 Soldering and Assembly Guidelines

The primary assembly method is reflow soldering. The datasheet provides a recommended reflow profile, specifying a peak temperature of 260\u00b0C. The critical parameter is that the temperature at the component body should not exceed the maximum temperature rating during assembly. The condition explicitly states soldering at 260\u00b0C for 3 seconds when measured at a point 1/16 inch below the seating plane. This guideline is essential for process engineers to set up the reflow oven conveyor speed and zone temperatures correctly to avoid thermal shock or degradation of the materials while ensuring a reliable solder joint.

1.4 Application Suggestions

1.4.1 Typical Application Scenarios

This display is ideal for any device requiring a clear, single-digit numeric readout. Common applications include: panel meters for voltage, current, or temperature; timers and counters; household appliances like ovens, microwaves, or washing machines; test and measurement equipment; industrial control panels; and medical devices. The high contrast and brightness make it suitable for applications where the display may be viewed from a distance or in high-ambient-light conditions.

1.4.2 Design Considerations

When integrating the LTS-4301SW, designers must consider current limiting. A series resistor is mandatory for each segment anode (or a current-regulated driver) to set the forward current to the desired level, typically between 5-20 mA, depending on the required brightness and thermal environment. The derating curve for forward current must be respected if the operating ambient temperature is expected to be high. The common cathode configuration requires the driver circuit to sink current. When multiplexing multiple digits (though this is a single-digit unit, the principle applies to systems using several of them), a suitable driver IC capable of sourcing current to the anodes and sinking the aggregated cathode current is needed. PCB layout should ensure clean power traces to minimize noise.

1.5 Technical Comparison and Differentiation

Compared to similar single-digit displays, the LTS-4301SW's use of InGaN white LED technology offers advantages over older technologies like red GaAsP LEDs or filtered white light. InGaN LEDs generally provide higher efficiency and brightness. The black face with white segments is a key differentiator from displays with a gray or light-colored face, offering superior contrast ratio, which is a critical factor for readability. The specified luminous intensity matching ratio (2:1) ensures segment uniformity, which is not always guaranteed in lower-cost displays. The wide operating temperature range (-35\u00b0C to +105\u00b0C) also makes it more robust for industrial or outdoor applications compared to displays with a narrower range.

1.6 Frequently Asked Questions Based on Technical Parameters

Q: What is the purpose of the two common cathode pins (3 and 8)?
A: They are internally connected. Having two pins helps distribute the total cathode current (which is the sum of currents from all illuminated segments) across two solder joints and PCB traces, improving current handling capacity, thermal performance, and mechanical connection reliability.

Q: How do I calculate the series resistor value for a segment?
A: Use Ohm's Law: R = (V_supply - V_F) / I_F. For example, with a 5V supply, a typical V_F of 3.15V, and a desired I_F of 10 mA: R = (5 - 3.15) / 0.01 = 185 ohms. Use the nearest standard value (e.g., 180 or 200 ohms). Always consider power rating: P = I_F² * R.

Q: Can I drive this display directly from a microcontroller pin?
A: It depends on the MCU's pin current sourcing capability. A typical MCU pin might source 20-25 mA, which is enough for one segment at full current. However, driving multiple segments or the common cathode (which sinks the sum of all segment currents) usually exceeds a single pin's capability. Dedicated driver ICs (e.g., 74HC595 shift register with current-limiting resistors, or a constant current LED driver) are strongly recommended for reliable and safe operation.

Q: What does \"categorized for luminous intensity\" mean?
A: It implies that during manufacturing, the LED chips or finished displays may be tested and sorted (binned) based on their measured luminous intensity. This allows customers to select parts with a specific brightness range for consistency in their product, especially when using multiple displays.

1.7 Practical Design and Usage Case

Consider designing a simple digital thermometer with a 0-9\u00b0C readout. One LTS-4301SW would display the units digit. A temperature sensor's digital output would be processed by a microcontroller. The MCU would decode the digit value (0-9) into the corresponding segment pattern (e.g., for '5', segments A, F, G, C, D are ON). The MCU would use a port expander or shift register to source current to the segment anodes (pins 1,2,4,5,6,7,9,10) through current-limiting resistors. The common cathode (pins 3 & 8) would be connected to a ground pin capable of sinking the total current (e.g., 8 segments * 10 mA = 80 mA), likely requiring a transistor. The black face ensures the '5' is easily readable on the device's panel.

1.8 Operating Principle Introduction

A seven-segment display works on a simple principle: it is a collection of seven independently controlled LED bars (segments) arranged in a figure-eight pattern. By turning on specific combinations of these segments, all ten decimal digits (0-9) can be formed. For instance, to display the number '7', segments A, B, and C are illuminated. The decimal point is an additional separate LED. Electrically, each segment is a standard LED with an anode and cathode. In a common cathode type like the LTS-4301SW, all cathodes are connected together to a common terminal. To light a segment, a positive voltage (through a current-limiting resistor) is applied to its specific anode pin, while the common cathode is connected to ground, completing the circuit.

1.9 Technology Trends and Developments

The trend in seven-segment displays has been towards higher efficiency, brightness, and miniaturization. The move from traditional colored LEDs (red, green) to phosphor-converted white LEDs (like the InGaN-based chip in this display) allows for a neutral, high-contrast appearance suitable for more applications. There is also a trend towards surface-mount device (SMD) packages for automated assembly, though through-hole types like this one remain popular for prototyping, repair, and applications requiring robust mechanical connections. Integration is another trend, with driver electronics and sometimes microcontrollers being combined with the display module itself, reducing external component count. Furthermore, advancements in materials are leading to wider viewing angles and improved performance over extended temperature ranges.