LTC-46454JF LED Display Datasheet - 0.4-inch Digit Height - Yellow-Orange Color - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTC-46454JF is a quadruple-digit, seven-segment alphanumeric display module designed for applications requiring clear, bright numeric readouts. Its primary function is to visually represent numerical data, commonly used in instrumentation, industrial control panels, consumer electronics, and test equipment. The core advantage of this device lies in its utilization of advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for the LED chips, which provides superior performance compared to older technologies like standard GaAsP LEDs.

The target market includes designers and engineers developing products where power efficiency, readability, and reliability are critical. This includes portable battery-operated devices, panel meters, medical equipment displays, and any system requiring a consistent, low-maintenance visual output. The device's low current requirement makes it particularly suitable for energy-sensitive applications.

2. Technical Parameter Deep Dive

2.1 Photometric and Optical Characteristics

The optical performance is defined under standard test conditions at an ambient temperature (Ta) of 25\u00b0C. The key parameter, Average Luminous Intensity (Iv), has a typical value of 650 \u00b5cd when driven at a forward current (IF) of 1mA per segment. This measurement is taken using a sensor and filter that approximates the CIE photopic eye-response curve, ensuring the value correlates with human visual perception. The wide range from a minimum of 200 \u00b5cd to the typical 650 \u00b5cd indicates a potential binning process for brightness.

The color characteristics are defined by wavelength. The Peak Emission Wavelength (\u03bbp) is typically 611 nm, while the Dominant Wavelength (\u03bbd) is typically 605 nm, both measured at IF=20mA. The difference between peak and dominant wavelength is normal for LEDs and relates to the shape of the emission spectrum. The Spectral Line Half-Width (\u0394\u03bb) is 17 nm, which describes the width of the emitted light spectrum at half its maximum intensity. A narrower half-width indicates a more pure, saturated color. The combination of these parameters defines the display's distinctive yellow-orange hue.

2.2 Electrical Characteristics

The electrical parameters define the operating limits and conditions for the display. The Absolute Maximum Ratings set the boundaries for safe operation. The Continuous Forward Current per segment is rated at 25 mA at 25\u00b0C, with a derating factor of 0.33 mA/\u00b0C. This means the maximum allowable continuous current decreases as the ambient temperature rises above 25\u00b0C to prevent overheating and damage. For pulsed operation, a Peak Forward Current of 90 mA is allowed under specific conditions: a 1/10 duty cycle and a 0.1ms pulse width. The maximum Reverse Voltage per segment is 5V; exceeding this can damage the LED junction.

The key operating parameter is the Forward Voltage (VF), which is typically 2.6V with a maximum of 2.6V at a test current of 20mA per segment. The minimum is listed as 2.05V. This Vf range is crucial for designing the current-limiting circuitry. The Reverse Current (IR) is specified at a maximum of 100 \u00b5A when a reverse voltage (VR) of 5V is applied, indicating the leakage current in the off-state.

2.3 Thermal and Environmental Specifications

The device is rated for an Operating Temperature Range of -35\u00b0C to +85\u00b0C. This wide range ensures functionality in various environmental conditions, from industrial cold storage to hot enclosures. The Storage Temperature Range is identical (-35\u00b0C to +85\u00b0C). A critical assembly specification is the maximum Solder Temperature: 260\u00b0C for a maximum duration of 3 seconds, measured at 1.6mm below the seating plane. This guideline is essential for wave soldering or reflow processes to prevent thermal damage to the LED chips or the epoxy package.

3. Binning System Explanation

While the datasheet does not explicitly detail a formal binning code, the specified ranges for key parameters imply that selection or binning occurs. The Luminous Intensity has a minimum of 200 \u00b5cd and a typical value of 650 \u00b5cd, suggesting devices may be sorted based on output brightness. The Luminous Intensity Matching Ratio is specified as 2:1 maximum. This ratio defines the maximum allowable variation in brightness between different segments within the same digit or between digits, ensuring visual uniformity. Devices would be tested to meet this criterion.

Similarly, the Forward Voltage (VF) has a range (2.05V to 2.6V at 20mA). Products might be grouped based on Vf to ensure consistent driving voltage requirements in a batch. The dominant and peak wavelength specifications also indicate a tight color control, which is a form of chromaticity binning.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristic Curves" on the final page. While the specific graphs are not provided in the text, standard curves for such devices typically include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph would show how light output increases with driving current. It is typically non-linear, with efficiency often dropping at very high currents due to thermal effects.
• Forward Voltage vs. Forward Current: This shows the diode characteristic of the LED. The voltage increases logarithmically with current.
• Relative Luminous Intensity vs. Ambient Temperature: This curve is critical for understanding thermal derating. The light output of AlInGaP LEDs generally decreases as the junction temperature increases.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the bell-shaped curve centered around 611 nm with a half-width of 17 nm.

These curves allow designers to predict performance under non-standard conditions, such as driving at a current between 1mA and 20mA, or operating at temperatures other than 25\u00b0C.

5. Mechanical and Package Information

The device is a standard 0.4-inch (10.0 mm) digit height display. The package dimensions are provided in a drawing (referenced but not detailed in text), with all dimensions in millimeters and standard tolerances of \u00b10.25 mm unless otherwise noted. The physical design features a gray face with white segments, which enhances contrast when the LEDs are off and diffuses the emitted light evenly when on, contributing to the "excellent character appearance" and "high contrast" mentioned in the features.

The pin connection diagram and internal circuit diagram are crucial for PCB layout. The device has a 13-pin configuration. It uses a multiplexed Common Anode architecture. Pins 6, 8, 9, and 12 are the common anodes for digits 4, 3, 2, and 1, respectively. Pin 13 is the common anode for the Upper Colon (UC) and Lower Colon (LC) indicators. The individual segment cathodes (A, B, C, D, E, F, G, DP) are brought out to separate pins. This configuration allows for multiplexed driving, where digits are illuminated one at a time in rapid succession, reducing the total number of required driver pins.

6. Soldering and Assembly Guidelines

The primary guideline provided is the solder temperature limit: a maximum of 260\u00b0C for a maximum of 3 seconds, measured at 1.6mm below the seating plane. This is a standard specification for through-hole components using wave soldering. Designers must ensure their soldering profile does not exceed this thermal shock. For manual soldering, a temperature-controlled iron should be used, and contact time with the pin should be minimized.

General handling precautions for LEDs apply: avoid mechanical stress on the epoxy lens, protect from electrostatic discharge (ESD) during handling, and store in appropriate anti-static, moisture-controlled environments if not used immediately.

7. Packaging and Ordering Information

The part number is LTC-46454JF. The "JF" suffix likely indicates a specific package type, pin configuration, or color variant (Yellow-Orange). The device is described as an "AlInGaP Yellow Orange Multiplex Common Anode" display with a "Right Hand Decimal" point. Standard packaging for such displays is typically in anti-static tubes or trays to protect the pins and lens during shipping and handling. Specific reel or tube quantities are not listed in the provided excerpt.

8. Application Suggestions

8.1 Typical Application Circuits

The common anode, multiplexed design is ideal for microcontroller-driven applications. A typical circuit involves using a microcontroller's I/O ports or a dedicated LED driver IC. The common anode pins would be connected to PNP transistors or P-channel MOSFETs (or directly to microcontroller pins if current sourcing capability is sufficient), which are switched to supply power to each digit sequentially. The segment cathode pins are connected to current-limiting resistors and then to NPN transistors, N-channel MOSFETs, or the sink-capable outputs of a driver IC/microcontroller. The current-limiting resistor value is calculated using the formula: R = (Vcc - Vf_led) / I_desired. With a Vcc of 5V, a typical Vf of 2.6V, and a desired segment current of 10mA, the resistor would be approximately (5 - 2.6) / 0.01 = 240 ohms.

8.2 Design Considerations

• Multiplexing Frequency: The refresh rate must be high enough to avoid visible flicker, typically above 60-100 Hz per digit. With 4 digits, the scanning frequency needs to be 4 times that.
• Peak Current: In a multiplexed design, the instantaneous current per segment is higher than the average current. If the average current per segment is targeted at 5mA with a 1/4 duty cycle (4 digits), the instantaneous current during its ON time would need to be 20mA. This must be checked against the maximum ratings.
• Heat Dissipation: At higher currents or in high ambient temperatures, ensure the power dissipation per segment (max 70mW) is not exceeded, considering the derating factor.
• Viewing Angle: The wide viewing angle is beneficial for panels that may be viewed from off-axis positions.

9. Technical Comparison

Compared to older red GaAsP LED displays, the AlInGaP technology in the LTC-46454JF offers significantly higher luminous efficiency. This means it can achieve the same or greater brightness at a lower drive current, directly enabling the "low power requirement" feature. It also typically offers better temperature stability and longer operational lifetime. Compared to contemporary high-brightness red LEDs, the yellow-orange color (605-611nm) provides excellent visibility and is often subjectively perceived as very bright. Compared to vacuum fluorescent displays (VFDs) or liquid crystal displays (LCDs), this LED display offers superior ruggedness, wider temperature range, faster response time, and does not require a backlight or high voltage supply, but at the cost of higher power consumption for multi-digit displays than LCDs.

10. Frequently Asked Questions (Based on Parameters)

Q: Can I drive this display with a 3.3V microcontroller power supply?
A: Yes. The typical forward voltage is 2.6V, leaving 0.7V to be dropped across the current-limiting resistor at 3.3V. This is sufficient for operation, though the available voltage headroom for setting the current precisely is reduced compared to a 5V system.

Q: What is the minimum current needed to see a visible glow?
A: The datasheet specifies test conditions down to 1mA, where the typical luminous intensity is 650 \u00b5cd. It will likely be visible at even lower currents, though brightness will be very dim. The "low current characteristics" are a key feature.

Q: How do I control the decimal point and colons?
A: The decimal point (DP) has its own cathode pin (Pin 3). The upper and lower colons (UC, LC) share a common anode (Pin 13) and have their cathodes connected to the segment B cathode (Pin 7). To light a colon, you must activate digit common anode Pin 13 and pull the segment B cathode (Pin 7) low.

Q: Why is the reverse voltage rating only 5V?
A: LEDs are not designed to block reverse voltage. The PN junction can be easily damaged by small reverse biases. The 5V rating is a safety limit; circuit design should ensure reverse voltage is never applied, often using protection diodes in parallel with the LED in bidirectional signal applications.

11. Practical Use Case

Case: Designing a 4-Digit Voltmeter Readout. A designer is creating a benchtop power supply unit requiring a clear voltage readout. They select the LTC-46454JF for its brightness and readability. The system uses a microcontroller with an ADC to measure the output voltage. The microcontroller's firmware implements a multiplexing routine, cycling through the four digits. The segment patterns for numbers 0-9 are stored in a look-up table. The designer calculates current-limiting resistors for an average segment current of 8mA, considering the 1/4 duty cycle multiplexing (so instantaneous current is ~32mA, which is within the pulsed rating but they may reduce it to stay within continuous ratings). They use a 5V rail for the display. The gray face of the display blends well with the instrument's front panel, and the yellow-orange digits are easily visible under various lighting conditions in a lab.

12. Technology Principle Introduction

The core technology is the AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material system grown on a non-transparent GaAs (Gallium Arsenide) substrate. When a forward voltage is applied across the PN junction of this semiconductor, electrons and holes recombine, releasing energy in the form of photons (light). The specific wavelength of this light--in this case, yellow-orange around 611 nm--is determined by the bandgap energy of the AlInGaP alloy, which is engineered during the crystal growth process. The non-transparent GaAs substrate absorbs any light emitted downward, improving contrast by reducing internal reflection and scattering that could cause a "halo" effect around the segments. The seven-segment layout is a standardized pattern where different combinations of the segments (labeled A through G) are illuminated to form the numerals 0-9 and some letters.

13. Technology Trends

While discrete seven-segment LED displays like the LTC-46454JF remain relevant for specific applications requiring high brightness, simplicity, and robustness, the general trend in display technology has shifted towards integrated solutions. Dot-matrix LED displays and OLEDs offer greater flexibility for showing alphanumeric characters and graphics. For simple numeric readouts, LCDs dominate in ultra-low-power applications. However, the inherent advantages of LEDs--high brightness, self-emission, wide temperature range, and long lifetime--ensure their continued use in industrial, automotive, and outdoor equipment where these factors are paramount. Advances in LED materials, like more efficient AlInGaP and the rise of GaN-based blue/green/white LEDs, have expanded color options and efficiency for newer display products.