The **78250MC-R** is a high-performance, surface-mount (SMD) interface transformer specifically designed for use with the MAX250 and MAX251 isolated RS-232 transceiver chipsets from Maxim Integrated. It is manufactured by Murata Power Solutions. --- ### 1. Key Technical Specifications | Parameter | Value | | :--- | :--- | | **Manufacturer** | Murata Power Solutions | | **Turns Ratio** | 1:1:1 (Primary to Secondary) | | **Input Voltage** | 5.0V (Optimized for 5V logic) | | **Isolation Voltage** | 4000 Vrms | | **Mounting Type** | Surface Mount (SMD/SMT) | | **Package / Case** | 6-SMD (Gull Wing) | | **Operating Temperature** | -40°C to +85°C | --- ### 2. Core Functional Role The primary purpose of the 78250MC-R is to provide **galvanic isolation** for power and data lines. * **Power Transfer:** It works in a "push-pull" configuration to transfer power from the logic side (non-isolated) to the line side (isolated). * **Voltage Conversion:** In conjunction with the MAX250/251, it helps generate the ±10V required for RS-232 communication from a single +5V supply. * **Safety & Noise:** It protects sensitive microcontrollers from high-voltage surges on the RS-232 cable and eliminates ground loops. --- ### 3. Pin Configuration (Typical) The device usually features a 6-pin layout to accommodate the primary and secondary windings: | Pin Number | Function | Description | | :--- | :--- | :--- | | **1 - 3** | Primary Winding | Connected to the driver (e.g., MAX250) | | **4 - 6** | Secondary Winding | Provides isolated output to the transceiver side | --- ### 4. Critical Design Considerations When integrating this part into a PCB layout, consider the following: * **Creepage and Clearance:** Ensure the PCB layout maintains the distance between the primary and secondary pads to preserve the 4kV isolation rating. * **Toroidal Core:** This part uses a toroidal core which offers high efficiency and low electromagnetic interference (EMI). * **Reflow Soldering:** The "MC-R" suffix indicates it is compatible with standard lead-free reflow soldering processes and is typically supplied on Tape & Reel. ---