### FSUSB73: High-Speed USB 2.0 3:1 Multiplexer The **FSUSB73** is a high-performance, low-power bi-directional 3:1 USB switch designed specifically for switching high-speed USB 2.0 signals. It allows three USB sources to share a single USB port or vice versa. --- ### Key Technical Specifications | Feature | Description | | :--- | :--- | | **Function** | 3:1 High-Speed USB 2.0 Switch (DP/DM) | | **Operating Voltage (VCC)** | 2.4V to 4.5V | | **Bandwidth** | 720 MHz | | **On Resistance (Ron)** | 6.5 $\Omega$ (Typical) | | **Shutdown Current** | < 1 $\mu$A | | **Package Type** | 16-Lead UMLP (Ultra-thin MLP) | --- ### Internal Functional Parts The FSUSB73 consists of several internal architectural components that ensure signal integrity for high-speed data: 1. **Analog Switches (Pass Gates):** The core of the device. These are low-capacitance switches that route the Differential Pair (D+ and D-) signals. High bandwidth (720 MHz) is maintained to minimize edge distortion of the 480 Mbps USB 2.0 signal. 2. **Selection Logic (S0, S1):** Two control pins determine which of the three paths is active. The logic table is typically as follows: * `00`: Port 1 Active * `01`: Port 2 Active * `10`: Port 3 Active * `11`: High Impedance (All disconnected) 3. **Charge Pump / Internal Drivers:** Ensures that the switches remain linear even as the input signal approaches the supply voltage, preventing signal clipping. --- ### Core Applications * **Mobile Handsets:** Switching between a micro-USB connector and internal modules (e.g., Application Processor vs. Modem). * **Tablets & Laptops:** Routing USB data lines to different peripherals or docking stations. * **Media Players:** Handling data transfer and charging synchronization. --- ### Design Considerations 1. **Impedance Matching:** To maintain USB 2.0 compliance, the PCB traces should be designed for 90 $\Omega$ differential impedance. 2. **Power Sequencing:** The device is "Power-Off Isolation" capable, meaning it protects the system if signals are present on the data lines while the VCC of the FSUSB73 is at 0V. 3. **ESD Protection:** While the FSUSB73 has built-in ESD protection, external TVS diodes are often recommended for ports exposed to the outside world.