LTC-5689TBZ Blue 7-Segment LED Display Datasheet - 0.56-inch Digit Height - 3.6V Forward Voltage - InGaN Blue Chip - English Technical Document

1. Product Overview

The LTC-5689TBZ is a high-performance, triple-digit, seven-segment alphanumeric display module. It is designed for applications requiring clear, bright numeric readouts with excellent visibility. The core component of this display is an InGaN (Indium Gallium Nitride) blue LED chip epitaxially grown on a sapphire substrate, which provides stable and efficient light emission. A key integrated feature is a Zener diode for each segment, offering protection against reverse voltage spikes, a critical factor for enhancing the long-term reliability of the display in electrically noisy environments.

The display features a black face with white segments, creating a high-contrast appearance that significantly improves readability under various lighting conditions. It is categorized as a Common Anode type display, which is a standard configuration for multiplexed driving circuits commonly used in microcontroller-based systems. The device is compliant with RoHS (Restriction of Hazardous Substances) directives, ensuring it is manufactured with lead-free materials.

1.1 Core Advantages and Target Market

The primary advantages of the LTC-5689TBZ stem from its optoelectronic design and robust construction. The use of InGaN technology delivers high brightness and a consistent blue color with a dominant wavelength typically around 470-475 nm. The continuous, uniform segments ensure a professional and seamless character appearance, which is crucial for user interfaces in consumer electronics, industrial control panels, instrumentation, and test equipment.

Its low power requirement makes it suitable for battery-powered or energy-conscious devices. The wide viewing angle ensures the display remains legible even when viewed from the side, expanding its usability in panel-mounted applications. The solid-state reliability of LEDs, combined with the added Zener diode protection, makes this display a durable choice for applications demanding long operational life and stability.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

Understanding the absolute maximum ratings is essential for preventing device failure during circuit design and operation. The ratings define the limits beyond which permanent damage may occur.

• Power Dissipation per Segment: 70 mW. This is the maximum power that can be safely dissipated as heat by a single illuminated segment under continuous operation.
• Peak Forward Current per Segment: 100 mA. This current is permissible only under pulsed conditions with a 1/10 duty cycle and a 0.1 ms pulse width. It should not be used for calculating normal operating conditions.
• Continuous Forward Current per Segment: 20 mA at 25°C. This is the recommended maximum current for standard operation. A linear derating factor of 0.21 mA/°C applies as the ambient temperature (Ta) increases above 25°C. For example, at 50°C, the maximum continuous current would be approximately 20 mA - (0.21 mA/°C * 25°C) = 14.75 mA.
• Operating & Storage Temperature Range: -35°C to +85°C. The device is rated for industrial temperature ranges.
• Solder Conditions: The device can withstand wave soldering or reflow processes where the solder temperature at 1/16 inch (approx. 1.6 mm) below the seating plane is 260°C for a maximum of 3 seconds.

2.2 Electrical & Optical Characteristics (Ta=25°C)

These parameters are measured under specific test conditions and represent the typical performance of the device.

• Average Luminous Intensity (Iv): 5400 - 9000 µcd (microcandelas) at a forward current (IF) of 10 mA. This wide range indicates the device is binned or categorized for intensity. Designers must account for this variation when aiming for consistent brightness across multiple units or displays.
• Forward Voltage per Segment (VF): 3.3V (Min), 3.6V (Typ) at IF=20 mA. This parameter is crucial for designing the current-limiting resistor value. Using a standard 5V supply, the resistor value would be R = (Vcc - VF) / IF = (5V - 3.6V) / 0.020A = 70 Ohms. A slightly higher value (e.g., 75-100 Ohms) is often used for reliability and to account for VF variation.
• Peak Emission Wavelength (λp): 468 nm (Typ). This is the wavelength at which the emitted light intensity is highest.
• Dominant Wavelength (λd): 470 - 475 nm (Typ). This is the wavelength perceived by the human eye and defines the color of the LED.
• Spectral Line Half-Width (Δλ): 25 nm (Typ). This indicates the spectral purity; a smaller value means a more monochromatic light.
• Reverse Current per Segment (IR): 100 µA (Max) at a Reverse Voltage (VR) of 5V. Critical Note: This test condition is for quality assurance (IR test) only. The device is NOT designed to operate continuously under reverse bias. The integrated Zener diode is intended for transient protection, not for steady-state reverse voltage operation.
• Luminous Intensity Matching Ratio: 2:1 (Max). This specifies the maximum allowable ratio between the brightest and dimmest segments within a single digit or across similar lit areas, ensuring visual uniformity.

3. Binning and Categorization System

The datasheet explicitly states the device is \"Categorized for Luminous Intensity.\" This is a common practice in LED manufacturing to group products based on measured performance parameters.

• Luminous Intensity Binning: The Iv range of 5400-9000 µcd suggests multiple intensity bins. For applications requiring consistent brightness (e.g., multi-digit displays or panels with several units), specifying a tighter bin or sourcing from the same production lot is advisable.
• Wavelength/Color Binning: While not explicitly detailed with codes, the typical λd range of 470-475 nm implies potential color sorting. Consistent dominant wavelength is key for uniform color appearance.
• Forward Voltage Sorting: The VF range (3.3V to 3.6V) may also be subject to categorization, which can affect power supply design and thermal management in large arrays.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical/Optical Characteristic Curves.\" While the specific graphs are not provided in the excerpt, standard LED curves can be inferred and are critical for design.

• Forward Current vs. Forward Voltage (I-V Curve): An LED exhibits an exponential I-V relationship. The specified VF at 20 mA gives one point on this curve. The curve shows the turn-on voltage and how current increases rapidly with voltage above this point, highlighting the necessity of current-limiting mechanisms.
• Luminous Intensity vs. Forward Current (L-I Curve): Light output is generally proportional to forward current, but it can saturate at high currents due to thermal effects. Operating at or below the recommended 20 mA ensures linearity and longevity.
• Luminous Intensity vs. Ambient Temperature: LED light output decreases as junction temperature increases. The derating of continuous current (0.21 mA/°C) is directly related to managing this thermal effect to maintain brightness and reliability.
• Spectral Distribution: The graph would show the relative intensity of emitted light across wavelengths, centered around 470-475 nm with a typical half-width of 25 nm.

5. Mechanical, Package & Pinout Information

5.1 Package Dimensions

The display has a digit height of 0.56 inches (14.2 mm). All mechanical dimensions are provided in millimeters with a standard tolerance of ±0.25 mm unless otherwise specified. A specific note mentions a pin tip shift tolerance of +0.4 mm, which is important for PCB footprint design to ensure proper alignment and solderability.

5.2 Internal Circuit Diagram and Pin Connection

The internal circuit diagram reveals the architecture: each segment (A-G, DP1-5) is an individual InGaN blue LED chip in series with a Zener diode. All these LED-Zener pairs share a common anode connection per digit. The pinout is as follows:

• Pins 1-7: Cathodes for segments A, B, C, D, E, F, G respectively.
• Pin 8: Common cathode for the three right-hand decimal points (DP1, DP2, DP3).
• Pins 9, 10, 11: Common anodes for Digit 3, Digit 2, and Digit 1 respectively. This is the power supply point for each digit.
• Pin 12: Common anode for the two left-hand decimal points (DP4, DP5).
• Pins 13, 14: Cathodes for DP5 and DP4 respectively.

This configuration is ideal for multiplexing. By sequentially driving the common anodes (pins 9,10,11,12) HIGH and sinking current through the appropriate segment cathode pins, all three digits and five decimal points can be controlled with a relatively low pin count from a microcontroller.

6. Soldering, Assembly & Handling Guidelines

Adherence to soldering specifications is critical. The device can withstand a maximum solder temperature of 260°C for 3 seconds, measured 1.6 mm below the package body. Standard lead-free reflow profiles (IPC/JEDEC J-STD-020) are generally applicable. Care must be taken to avoid mechanical stress on the pins during insertion and to prevent excessive heating during hand soldering. For storage, the recommended range is -35°C to +85°C in a dry, non-condensing environment.

7. Application Notes and Design Considerations

7.1 Typical Application Circuits

The most common drive method is multiplexing. A microcontroller will use output pins to control transistor switches (e.g., PNP or P-channel MOSFETs) on the common anode lines and use sink-capable I/O ports or driver ICs (like 74HC595 shift registers with ULN2003 darlington arrays) on the cathode lines. A current-limiting resistor is required for each cathode line (or built into the driver). The multiplexing frequency should be high enough to avoid flicker (typically >60 Hz).

7.2 Design Considerations

• Current Limiting: Always use series resistors. Calculate based on the worst-case (minimum) VF to avoid overcurrent.
• Multiplexing Duty Cycle: Since each digit is only powered for a fraction of the time, the instantaneous current per segment can be higher than the average to achieve the desired brightness. For example, in a 3-digit multiplex, the duty cycle per digit is ~1/3. To achieve an average current of 10 mA, the instantaneous current during its active time could be set to 30 mA, provided it does not exceed the peak current rating and the average power dissipation is within limits.
• Zener Diode Function: The integrated Zener diode clamps any negative voltage transients on the segment, protecting the delicate LED chip. It does not regulate voltage during normal forward operation.
• Viewing Angle and Mounting: Ensure the display is mounted squarely on the PCB and that the panel cutout aligns correctly to maximize the wide viewing angle benefit.

8. Technical Comparison and Differentiation

Compared to standard seven-segment displays without protection diodes, the LTC-5689TBZ offers significantly improved resilience against electrical overstress from back-EMF, inductive switching, or wiring errors. Compared to displays using older GaP or GaAsP technology, the InGaN blue chip provides higher brightness and a more vibrant, saturated blue color. The 0.56-inch digit height places it in a category suitable for medium-range viewing, larger than miniature SMD displays but smaller than large panel meters.

9. Frequently Asked Questions (FAQ)

Q: Can I drive this display with a 3.3V microcontroller system?
A: Possibly, but with caution. The typical VF is 3.6V, which is higher than 3.3V. You may get very dim or no illumination. A boost circuit or a driver IC powered from a higher voltage (like 5V) would be required for the LED supply, while the control signals can remain at 3.3V logic levels.

Q: Why is there a reverse current (IR) specification if I shouldn't apply reverse voltage?
A: The IR test is a manufacturing quality check to ensure the Zener diode and LED junction are intact. It is not an operational guideline. Continuous reverse bias can degrade the device.

Q: How do I control the decimal points independently?
A: The five decimal points are split into two groups: DP1/DP2/DP3 (common cathode on Pin 8) and DP4/DP5 (individual cathodes on Pins 14 & 13, common anode on Pin 12). They must be driven accordingly in the multiplexing sequence.

10. Practical Application Example

Case: Designing a Simple 3-Digit Voltmeter Readout. A microcontroller with an ADC measures a voltage. The firmware converts the reading to three digits. Using a multiplexing routine, it activates Digit 1's anode (Pin 11), then sets the cathode pins (1-7, 8 for DP) to ground pattern for the first digit's value, waits a short interval, then deactivates Digit 1 and activates Digit 2 (Pin 10), and so on. The decimal point (e.g., DP2) is illuminated by activating its common anode group (Pin 12 for DP4/DP5, or included in the digit cycle for DP1/2/3) and pulling its specific cathode low during the correct digit's active period. Current-limiting resistors of 100 Ohms on each cathode line would provide a safe operating point from a 5V supply.

11. Operational Principle

The device operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's turn-on threshold (approximately 3.3-3.6V for this InGaN LED) is applied, electrons and holes recombine in the active region, releasing energy in the form of photons. The specific material composition (InGaN) determines the bandgap energy, which corresponds to the blue wavelength of the emitted light. The integrated Zener diode conducts heavily when a reverse voltage exceeds its breakdown voltage, thereby shunting harmful reverse current away from the LED junction and protecting it from damage.

12. Technology Trends

InGaN-based LEDs represent a mature and highly efficient technology for blue and green emission. Trends in display technology include a move towards higher pixel density (smaller segments or dot-matrix), integrated drivers and controllers within the display package, and the adoption of surface-mount device (SMD) packages for automated assembly. While discrete seven-segment displays remain vital for specific applications, their role is increasingly complemented by OLED and TFT LCD modules that offer greater flexibility for graphics and multi-color output. The integration of protection components like Zener diodes, as seen in the LTC-5689TBZ, reflects an industry focus on improving robustness and reliability in cost-sensitive applications.