The **KRTB-4AB-R** is a specific electronic component manufactured by **Rohm Semiconductor**. It is a high-efficiency, multi-color **SMD (Surface Mount Device) LED** designed for high-density mounting and compact display applications. --- ## 1. Core Technical Specifications The KRTB-4AB-R belongs to the **PICOLED™-RGB** series. Its primary feature is the integration of three distinct LED chips (Red, Green, and Blue) within a single, ultra-small package. | Feature | Specification | | :--- | :--- | | **Package Size** | 1.0 mm x 1.0 mm (1010 Metric) | | **Colors** | RGB (Red, Green, Blue) | | **Luminous Intensity** | R: 28mcd, G: 56mcd, B: 14mcd (Typical) | | **Forward Voltage (Vf)** | R: 2.0V, G: 2.9V, B: 2.9V | | **Operating Temp** | -40°C to +85°C | | **Mounting Type** | Surface Mount (SMD) | --- ## 2. Key Components and Materials The part is constructed using high-performance semiconductor materials tailored for each color spectrum: 1. **Red Die:** Typically uses **AlGaInP** (Aluminum Gallium Indium Phosphide) technology to achieve high brightness at lower voltages. 2. **Green & Blue Die:** Utilizes **InGaN** (Indium Gallium Nitride) technology, which is standard for high-efficiency blue and green light emission. 3. **Encapsulation:** The internal chips are covered with a transparent epoxy resin to protect the wire bonds while allowing maximum light transmission. --- ## 3. Circuit Configuration The KRTB-4AB-R utilizes a **Common Anode** or **Common Cathode** configuration (depending on the specific sub-wiring of the PicoLED series, though most are individual terminal types for full control). ### Connection Diagram (Internal Logic) ```text [Red Anode] ----|>|---- [Red Cathode] [Green Anode] --|>|---- [Green Cathode] [Blue Anode] ---|>|---- [Blue Cathode] ``` *Note: Because all six terminals (3 anodes, 3 cathodes) are often accessible in this package style, it allows for independent current control for precise color mixing.* --- ## 4. Typical Applications Due to its incredibly small footprint (1.0 x 1.0 mm), this part is commonly found in: * **Mobile Devices:** Indicator lights for smartphones and tablets. * **Wearables:** Status LEDs for smartwatches and fitness trackers. * **Matrix Displays:** High-resolution indoor LED signage. * **Backlighting:** Small-scale illumination for buttons or switches. --- ## 5. Design Considerations * **Current Limiting:** Like all LEDs, the KRTB-4AB-R requires series resistors to prevent thermal runaway. Because the Forward Voltage ($V_f$) differs between Red and Blue/Green, different resistor values must be calculated for each channel. * **Thermal Management:** Despite its small size, the heat generated by three dies in a 1mm² area can be significant. Proper PCB copper padding is required for heat dissipation.