The **M3H28FAD-R** is a high-performance, radiation-hardened (Rad-Hard) isolated DC-DC converter designed primarily for aerospace, defense, and satellite applications. It belongs to the M3H series manufactured by IR HiRel (an Infineon Technologies company). --- ## 1. Technical Specifications Below are the key electrical characteristics of the M3H28FAD-R: | Feature | Specification | | :--- | :--- | | **Input Voltage Range** | 18V to 40V DC (28V Nominal) | | **Output Voltage** | Dual Output: ±12V or ±15V (Configurable) | | **Output Power** | 25 Watts | | **Efficiency** | Up to 82% | | **Isolation** | 100MΩ @ 500VDC | | **Operating Temp** | -55°C to +125°C | | **Package** | Hermetic, Flangeless Mount | --- ## 2. Key Electronic Components & Features The "FAD" suffix indicates specific architectural choices in the circuitry: ### A. Radiation Hardness Assurance (RHA) The internal components are selected and tested to withstand harsh space environments: * **TID (Total Ionizing Dose):** Rated for up to 100 krad(Si). * **SEE (Single Event Effects):** Immune to Single Event Latch-up (SEL) and tolerant to Single Event Burnout (SEB) up to an LET of 82 MeV·cm²/mg. ### B. Magnetic Feedback System Unlike commercial converters that use optoisolators (which degrade under radiation), the M3H28FAD-R uses **magnetic coupling** for the feedback loop. This ensures long-term stability and reliability in high-radiation orbits (LEO, MEO, GEO). ### C. Protection Circuitry The device incorporates several integrated protection layers: * **Overload/Short Circuit Protection:** Uses a "hiccup" mode or current limiting to prevent thermal runaway. * **Under-Voltage Lockout (UVLO):** Ensures the device does not attempt to start up until the input voltage is sufficient for stable operation. * **Soft Start:** Gradually increases output voltage to prevent high inrush currents during startup. --- ## 3. Physical Layout & Pinout Concepts The unit is housed in a hermetically sealed, ceramic-to-metal package to prevent outgassing in a vacuum. ```text Typical Functional Blocks: [Input Filter] -> [PWM Controller] -> [Power MOSFETs] -> [Transformer] -> [Rectifier/Filter] ^ | |-------[Magnetic Feedback]-----| ``` --- ## 4. Part Number Decoder Understanding the "M3H28FAD-R" nomenclature: * **M3H:** Series name (High-efficiency Rad-Hard). * **28:** Nominal Input Voltage (28V). * **F:** Dual Output. * **AD:** Voltage Code (typically representing the ±12V/±15V adjustable range). * **R:** Radiation Rating (R = 100k Rads).