SMD RGB LED LTSA-E35BCEGBW Datasheet - 12mm Package - 5V Supply - ISELED Protocol - English Technical Documentation

1. Product Overview

This document details the specifications for a high-performance, surface-mount RGB LED module designed for demanding automotive accessory applications. The device integrates red, green, and blue LED chips with a dedicated driver IC that supports the ISELED digital communication protocol. This integration enables precise color control, daisy-chaining of multiple units, and advanced features like temperature compensation directly within the LED package.

1.1 Core Features and Advantages

The primary advantage of this product is its combination of high-brightness LED performance with intelligent digital control in a compact SMD package. Key features include:

• Digital Serial Interface: Utilizes a bidirectional, half-duplex ISELED-compliant serial communication bus operating at 2 Mbit/s. This allows for precise 8-bit brightness control for each color channel and enables the connection of up to 4079 devices in a single chain, simplifying wiring in complex lighting systems.
• Integrated Intelligence: The onboard driver IC handles PWM generation for color mixing and features an integrated ADC for temperature sensing. It automatically applies compensation to the red LED's drive current to maintain consistent luminous output across the operating temperature range.
• Automotive Robustness: The component is qualified according to AEC-Q102 for the LED dice and AEC-Q100 for the driver IC. It is preconditioned to JEDEC Level 2 moisture sensitivity and is compatible with lead-free infrared reflow soldering processes.
• Design for Manufacturing: Supplied in 12mm tape on 7-inch reels, the package is compatible with standard automated pick-and-place and soldering equipment, facilitating high-volume production.

1.2 Target Market and Applications

The primary target market is the automotive industry, specifically for interior and exterior accessory lighting applications where reliable performance, precise color control, and networkability are required. Potential use cases include ambient lighting, status indicators, and decorative lighting elements.

2. Technical Parameters: In-Depth Objective Analysis

2.1 Absolute Maximum Ratings and Operating Conditions

Understanding the limits of operation is critical for reliable design. The device operates from a 4.5V to 5.5V supply, with a nominal voltage of 5.0V. The ambient operating temperature range is specified from -40°C to +110°C, with a maximum junction temperature of 125°C. The device is rated for ESD withstand voltage of 2 kV (HBM, Class H1C per AEC-Q101-001). Storage should be within -40°C to +125°C.

2.2 Photometric and Optical Characteristics

Optical performance is measured at a junction temperature of 25°C under full-brightness commands. Key metrics include:

• Luminous Intensity: The typical luminous intensity for individual colors is 530 mcd for Red (622 nm dominant wavelength), 1180 mcd for Green (527 nm), and 90 mcd for Blue (461 nm). When all three colors are driven at maximum (white light), the combined typical luminous intensity is 1800 mcd.
• Color Characteristics: The typical chromaticity coordinates for white light are x=0.3127, y=0.3290, which corresponds to the D65 white point. The viewing angle (2θ1/2) is 120 degrees, providing a wide, diffuse light pattern suitable for area illumination.
• Tolerances: Luminous intensity has a ±10% tolerance, dominant wavelength ±1nm, and chromaticity coordinate ±0.01. These are standard tolerances for mid-to-high-performance LEDs.

2.3 Electrical and Thermal Characteristics

The electrical characteristics reveal the device's power consumption and thermal management requirements.

• Current Consumption: The average current draw varies by color. Typical values are 26.7 mA for Red, 20.5 mA for Green, and 10.0 mA for Blue when each is driven individually at maximum brightness. The driver IC itself consumes a typical quiescent current (I_drv) of 1.2 mA.
• Thermal Resistance: The thermal resistance from the LED junction to the solder point (Rth_JS) is a critical parameter for heat dissipation. Typical values are 70.3 °C/W for the Red chip, 71 °C/W for Green, and 61.7 °C/W for Blue. These values are measured on an FR4 substrate with a 16mm² copper pad. Proper PCB thermal design is essential to keep the junction temperature below the 125°C maximum, especially when driving multiple colors simultaneously or at high ambient temperatures.

2.4 Power-On Reset and Communication Interface

The device features a power-on reset circuit with a typical threshold of 4.2V (min 4.0V, max 4.4V). The serial communication interface uses differential signaling on SIO_P and SIO_N pins, with voltage levels matching the Vcc supply range (4.5V to 5.5V).

3. Performance Curve Analysis

3.1 Temperature Dependence of Luminous Intensity

The provided graphs illustrate the relative luminous intensity (normalized to the value at 25°C) as a function of junction temperature for each primary color and for white. A key observation is the significant drop in red LED intensity as temperature increases, which is a known characteristic of AlInGaP materials. This underscores the importance of the integrated temperature compensation feature, which adjusts the red PWM duty cycle to counteract this decline and maintain color stability.

3.2 Temperature Dependence of Chromaticity

Additional graphs show the shift in chromaticity coordinates (ΔCx, ΔCy) with junction temperature. These shifts are most pronounced for the red and blue channels. The data provides a basis for understanding color drift in uncompensated operation and highlights the value of the onboard compensation and potential for system-level color calibration using the digital interface.

4. Mechanical and Package Information

4.1 Package Dimensions and Outline

The device uses a surface-mount package. The dimensional drawing indicates the physical footprint and height. All critical dimensions are provided in millimeters with a general tolerance of ±0.2 mm unless otherwise specified. The lens is diffused to achieve the wide 120-degree viewing angle.

4.2 Pin Configuration and Function

The device has an 8-pin configuration:

1. PRG5: Ground (for LED manufacturing/test).
2. SIO1_N: Serial Communication Master Side, Negative differential line.
3. SIO1_P: Serial Communication Master Side, Positive differential line.
4. GND: Ground (Pin 4).
5. GND: Ground (Pin 5).
6. SIO2_P: Serial Communication Slave Side, Positive differential line (for daisy-chaining).
7. SIO2_N: Serial Communication Slave Side, Negative differential line.
8. Vcc_5V: IC Power Supply (5V).

The dual ground pins (4 & 5) and separate communication ports facilitate robust power distribution and easy daisy-chaining of multiple devices.

5. Soldering and Assembly Guidelines

5.1 IR Reflow Soldering Profile

A recommended reflow profile for lead-free (Pb-free) soldering is provided, conforming to J-STD-020B. The profile specifies key parameters including preheat, soak, reflow peak temperature (260°C maximum for 10 seconds), and cooling rates. Adhering to this profile is crucial to prevent thermal damage to the LED chips, the driver IC, and the internal wire bonds, ensuring long-term reliability.

5.2 Handling and Storage Notes

The device is preconditioned to JEDEC Level 2. This means the moisture-sensitive components are baked and packaged with a desiccant. Once the sealed dry bag is opened, the components must be assembled within a specified timeframe (typically 1 year at <10% RH, or shorter times at higher humidity) or be rebaked according to the manufacturer's instructions to prevent \"popcorning\" during reflow.

6. Functional Description and System Architecture

6.1 Internal Block Diagram Overview

The functional block diagram reveals an integrated system. The core is a \"Main Unit\" microcontroller that manages communication, PWM generation, and system functions. It receives commands via the ISELED serial interface. Three independent, configurable constant-current sinks drive the Red, Green, and Blue LED anodes (low-side drive). An integrated Analog-to-Digital Converter (ADC) periodically measures the device temperature via an internal sensor. This data is used by the Main Unit to dynamically adjust the PWM duty cycle for the red LED, compensating for its thermal droop. The ADC can also be commanded to measure other analog values. A One-Time Programmable (OTP) non-volatile memory stores individual device calibration data (e.g., for LED forward voltage variations), which is loaded into registers at power-up.

6.2 PWM and Communication Protocol

Brightness for each color is controlled via Pulse-Width Modulation (PWM) with 8-bit resolution (256 levels). The ISELED protocol handles the transmission of these brightness values, device addressing, and read-back of status information (like temperature). The bidirectional nature allows for diagnostic communication, verifying device presence and health in a chain.

7. Application Suggestions and Design Considerations

7.1 Typical Application Circuits

In a typical application, a host microcontroller with an ISELED transceiver would connect to the SIO1_P/N pins of the first LED in a chain. The SIO2_P/N pins of that LED connect to the SIO1_P/N pins of the next LED, and so on. A single 5V power supply rail, adequately decoupled with local capacitors, powers all LEDs in the chain. The PCB layout must ensure low-impedance ground connections and proper thermal management by using adequate copper pour areas connected to the device's ground pins and thermal pad (if present in the footprint) to dissipate heat.

7.2 Design Considerations

• Thermal Management: Calculate the expected power dissipation (P = Vcc * I_total) and use the thermal resistance (Rth_JS) to estimate the temperature rise above the PCB solder point. Ensure the PCB design can conduct this heat away effectively to keep Tj < 125°C.
• Power Supply: The 5V supply must be stable and capable of supplying the peak current for the entire chain of LEDs. Consider inrush current during power-up.
• Signal Integrity: For long chains or in electrically noisy environments (like automotive), follow best practices for differential pair routing (length matching, controlled impedance if possible) for the SIO lines.

8. Technical Comparison and Differentiation

Compared to traditional analog RGB LEDs, this device offers significant advantages: Precision: Digital control eliminates color variations caused by forward voltage differences and analog driver tolerances. Simplicity: Reduces the number of control lines from multiple PWM lines per LED to a single differential pair for a whole chain. Intelligence: Built-in temperature compensation and calibration stored in OTP ensure consistent performance without complex external circuitry. Diagnostics: The bidirectional bus allows for system-level health monitoring. The main trade-off is the increased complexity of the digital communication protocol software compared to simple PWM generation.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: How many of these LEDs can I connect in series?
A: Up to 4079 devices can be connected in a single daisy chain via the ISELED interface.

Q: Does the temperature compensation work automatically?
A: Yes, the internal driver IC automatically measures temperature and adjusts the red LED's PWM duty cycle to maintain constant luminous intensity. This is a hardware feature independent of the host controller.

Q: What is the purpose of the OTP memory?
A: The OTP stores individual calibration data for each device, such as trim values for the current sinks or color calibration coefficients. This allows for very uniform performance across all units in a production batch.

Q: Can I use a 3.3V microcontroller to communicate with the 5V LED?
A: The SIO pins operate at the Vcc level (4.5-5.5V). Direct connection to a 3.3V logic device may not be reliable. A level shifter or an ISELED transceiver IC designed for lower voltage operation would be required.

10. Practical Use Case Example

Scenario: Automotive Door Panel Ambient Lighting. A designer wants to implement multi-zone, color-changing ambient lighting along the door panel and armrest. Using this LED, they can create a long chain of LEDs (e.g., 50 pieces) controlled by a single ISELED master located in the door module. Each LED can be individually addressed or grouped. The host can send commands to set any color or dynamic lighting pattern. The integrated temperature compensation ensures the red color intensity remains stable even when the door panel heats up from sunlight, preventing an unwanted color shift towards blue/green. The daisy-chain wiring drastically reduces the number of wires needed compared to a parallel RGB+driver solution, simplifying harness design and lowering cost and weight.

11. Operating Principle Introduction

The device operates on a mixed-signal principle. The digital core receives serial data, decodes commands, and sets registers that define the PWM duty cycles for three independent hardware PWM generators. These PWM signals drive low-side MOSFETs acting as constant-current sinks for the LEDs. The current level for each channel is fixed internally (likely set by the OTP calibration). The analog front-end includes the temperature sensor whose voltage output is digitized by the ADC. The digital logic uses this temperature reading to apply a predefined compensation curve, modifying the red PWM register value in real-time. This closed-loop control (sensing temperature, adjusting drive) happens autonomously within the device.

12. Technology Trends and Context

This product is part of a clear trend in LED lighting: the move from analog to digital, intelligent nodes. The ISELED protocol is a specific ecosystem developed for automotive lighting, competing with other standards like SPI-based addressable LEDs (e.g., WS2812B) or Automotive Ethernet. The integration of sensing (temperature) and processing directly into the LED package enables \"smart lighting\" where each point of light can be individually calibrated, monitored, and controlled. This facilitates advanced features like predictive maintenance (detecting LED degradation), complex adaptive lighting patterns, and seamless color matching across different materials and production batches. The focus on AEC-Q qualification and robust communication makes it suitable for the harsh electrical and environmental conditions of automotive applications, a key growth area for advanced LED technology.