The **R2248** is a specialized integrated circuit (IC) primarily designed for **Remote Control Systems**, specifically for infrared (IR) transmission. It is commonly paired with a receiver IC, such as the R2249. --- ### 1. General Overview The R2248 is an IR Remote Control Transmitter. It encodes data (button presses) into a serial stream of pulses that drive an IR LED. It is widely used in legacy consumer electronics like televisions, air conditioners, and toy controllers. ### 2. Technical Specifications | Feature | Description | | :--- | :--- | | **Supply Voltage (Vcc)** | 2.2V to 5.0V (Standard CMOS) | | **Operating Current** | Very low (typ. 1.0 $\mu$A in standby) | | **Transmission Frequency** | Typically 38kHz (carrier) | | **Maximum Functions** | Up to 18 commands (6 continuous + 12 single-shot) | | **Package Type** | DIP-16 or SOP-16 | ### 3. Key Electronic Sub-components (Internal) The IC consists of several functional blocks that manage the signal from the physical button press to the IR light output: 1. **Oscillator Circuit:** Requires an external ceramic resonator (typically 455kHz) to generate the precise clock frequency used for the carrier wave. 2. **Key Scan Logic:** Monitors the "Matrix" of buttons. It remains in sleep mode until a button press is detected to save battery. 3. **Data Encoder:** Converts the specific button input into a unique binary code. 4. **Carrier Generator:** Modulates the binary code onto a high-frequency carrier (usually 38kHz-40kHz) to allow the receiver to distinguish the signal from ambient light. 5. **Output Driver (REM Pin):** Provides the signal to an external transistor, which in turn drives the Infrared LED. --- ### 4. Typical Application Circuit To build a functional remote with the R2248, you need the following peripheral parts: * **Ceramic Resonator:** (455kHz) Connected to the OSC pins. * **Transistor:** (e.g., S8050) To amplify the current from the REM pin to the IR LED. * **IR LED:** To emit the light signal. * **Matrix Keypad:** A grid of switches connected to the "K" pins. * **Capacitors:** Small decoupling capacitors (e.g., 10$\mu$F and 0.1$\mu$F) to stabilize power. --- ### 5. Pin Configuration Summary | Pin Name | Function | | :--- | :--- | | **Vcc / Vss** | Power supply (Positive) and Ground. | | **OSC1 / OSC2** | Connection for the 455kHz resonator. | | **K1 - K6** | Key input lines for scanning the button matrix. | | **CODE** | Used to set a specific address so the remote doesn't interfere with other devices. | | **REM** | The modulated output signal sent to the IR LED driver. |