The **M3H28FBD-R** is a high-performance, radiation-hardened (Rad-Hard) isolated DC-DC converter specifically designed for space, satellite, and aerospace applications. It is manufactured by **Infineon (formerly International Rectifier/IR HiRel)**. --- ## 1. Core Specifications The device belongs to the **M3H series**, which is known for its high power density and reliability in harsh environments. | Parameter | Value / Range | | :--- | :--- | | **Input Voltage** | 18V to 50V (28V Nominal) | | **Output Voltage** | 3.3V, 5V, 12V, or 15V (Specific to the suffix) | | **Output Power** | Up to 40 Watts | | **Efficiency** | Typically 80% - 85% | | **Operating Temperature** | -55°C to +125°C | | **Isolation** | 100MΩ @ 500VDC | --- ## 2. Key Electronic Components & Features ### A. Power Stage & Topology The M3H series utilizes a **forward converter topology** with synchronous rectification. This design minimizes switching losses and allows for a high power-to-weight ratio, which is critical for launch costs in space missions. ### B. Radiation Hardening (The "Rad-Hard" Aspect) Unlike commercial DC-DC converters, the internal electronic components of the M3H28FBD-R are hardened against: * **Total Ionizing Dose (TID):** Guaranteed performance up to **100 krad(Si)**. * **Single Event Effects (SEE):** Rated for heavy ion irradiation up to an LET (Linear Energy Transfer) of **82 MeV·cm²/mg**. ### C. Magnetic Components It uses custom-designed, low-profile planar transformers and inductors. These provide better thermal management and mechanical stability under high vibration (launch conditions) compared to traditional wire-wound components. --- ## 3. Protection & Control Circuitry The internal circuitry includes several integrated protection layers: 1. **Under-Voltage Lockout (UVLO):** Prevents the device from operating when the input voltage is too low to ensure stable output. 2. **Soft-Start:** Internal timing circuitry that ramps up the output voltage gradually to prevent current surges. 3. **Overload/Short Circuit Protection:** Employs "hiccup mode" or constant current limiting to protect the internal MOSFETs. 4. **Remote Sense:** Compensates for voltage drops across the output leads to ensure precision at the load. --- ## 4. Physical Construction The "FBD" in the part number often refers to the package style: * **Case:** Hermetically sealed, ceramic-to-metal package. * **Weight:** Approximately 50-60 grams. * **Mounting:** Flanged package for secure bolting to a heat sink (chassis cooling). --- ## 5. Typical Application Diagram ```mermaid graph LR A[28V Bus] --> B[Input Filter] B --> C[PWM Controller] C --> D[Isolation Transformer] D --> E[Rectifier/Filter] E --> F[3.3V/5V/12V Output] F -- Feedback Loop --> C ```