### FSUSB74MPX: High-Speed USB 2.0 4-Port Switch The **FSUSB74MPX** is a high-performance, low-power, 4-port high-speed USB 2.0 (480 Mbps) switch manufactured by ON Semiconductor (formerly Fairchild). It is primarily used to multiplex a single USB port between four different USB peripherals. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Function** | 4:1 USB 2.0 Mux/Demux | | **Supply Voltage ($V_{CC}$)** | 2.4V to 4.4V | | **Data Rate** | Up to 480 Mbps (High Speed) | | **On Resistance ($R_{ON}$)** | 6.5 $\Omega$ (Typical) | | **Bandwidth (-3dB)** | 720 MHz | | **Operating Current** | < 1 $\mu$A (Ultra-low power) | | **Package** | MLP-16 (3.0 x 3.0 mm) | --- ### 2. Functional Description The FSUSB74MPX acts as a digital traffic controller for USB signals ($D+$ and $D-$). It ensures that the differential impedance is maintained so that signal integrity is not compromised during high-speed transfers. #### Pin Configuration Highlights: * **D+/D-**: The common USB signal lines connected to the host/connector. * **$1Dn+, 1Dn-$ to $4Dn+, 4Dn-$**: The four sets of differential output ports. * **S0, S1**: Selection pins used to determine which port is active. * **/OE (Output Enable)**: A control pin that enables the switch when pulled low. --- ### 3. Logic Selection Table The device uses two select pins ($S0$, $S1$) to route the signals: | /OE | S1 | S0 | Function | | :--- | :--- | :--- | :--- | | High | X | X | Disconnect (Hi-Z) | | Low | Low | Low | Port 1 Active | | Low | Low | High | Port 2 Active | | Low | High | Low | Port 3 Active | | Low | High | High | Port 4 Active | --- ### 4. Circuit Implementation Example When integrating this into a PCB design, the differential pairs must be routed with **90 $\Omega$ differential impedance**. ```c // Example Control Logic for Microcontroller void select_usb_port(int port) { digitalWrite(OE_PIN, LOW); // Enable Switch switch(port) { case 1: digitalWrite(S1, LOW); digitalWrite(S0, LOW); break; case 2: digitalWrite(S1, LOW); digitalWrite(S0, HIGH); break; case 3: digitalWrite(S1, HIGH); digitalWrite(S0, LOW); break; case 4: digitalWrite(S1, HIGH); digitalWrite(S0, HIGH); break; } } ``` --- ### 5. Applications * **Mobile Handsets:** Sharing a single micro-USB/USB-C port between data, charging, and factory programming. * **Tablets/Laptops:** Switching internal USB modules (e.g., Bluetooth, Camera, Fingerprint sensor). * **Automotive Infotainment:** Routing a user-facing USB port to different internal processors.