The term **"2248"** in electronics usually refers to one of two common components: the **BISS0001** (often used in the "HC-SR501" PIR motion sensor modules) which is historically linked to the "2248" numbering scheme, or more commonly, the **PT2248** Remote Control Transmitter IC. Below is an overview of the **PT2248**, as it is the most prominent discrete "2248" part. --- ## 1. Overview: PT2248 Infrared Transmitter The PT2248 is a CMOS integrated circuit designed for infrared remote control applications. It is frequently paired with the **PT2249** or **PT2250** receiver ICs. ### Key Specifications | Feature | Description | | :--- | :--- | | **Technology** | CMOS Technology (Low power consumption) | | **Voltage Range** | 2.2V to 5.0V | | **Channels** | Up to 18 functions (multi-channel capability) | | **Oscillator** | Built-in RC oscillator (requires external resistor) | | **Package** | 16-pin DIP or SOP | --- ## 2. Pin Configuration (16-Pin DIP) The PT2248 uses a matrix-style input system to handle multiple buttons with fewer pins. | Pin Number | Name | Function | | :--- | :--- | :--- | | 1 | **Vss** | Ground | | 2, 3 | **K1, K2** | Key input pins for the matrix | | 4-9 | **K3 - K6** | Key input pins (continued) | | 10-12 | **C1 - C3** | Code Bit pins (used to set the system address) | | 13 | **OSC** | Oscillator input (External Resistor/Capacitor) | | 14 | **DOUT** | Data Output (Connects to IR LED driver circuit) | | 15 | **CODE** | Logic switch for code selection | | 16 | **Vcc** | Power Supply (Positive) | --- ## 3. Working Principle 1. **Scanning:** The IC scans the key matrix (K1-K6). When a button is pressed, it completes a circuit between a Key pin and a Code pin. 2. **Encoding:** The internal logic generates a pulse-position modulated (PPM) signal based on the pressed key and the hard-wired address (C1-C3). 3. **Modulation:** The signal is output via the `DOUT` pin. 4. **Transmission:** The `DOUT` signal usually triggers a transistor (like an S8050) to drive an Infrared LED at a carrier frequency (typically 38kHz). --- ## 4. Typical Application Circuit The following is a simplified logic flow of how the PT2248 is integrated: ```text [ Battery ] ---> [ PT2248 IC ] <--- [ Key Matrix / Buttons ] | | (DOUT Pin) v [ Transistor Driver ] | [ Infrared LED ] ---> (IR Light Signal) ``` ### Common Use Cases: * Television remote controls. * Air conditioner remotes. * Toy remote controllers. * Garage door openers (older legacy systems).