Design Considerations for the Microchip USB2513B/M2 3-Port USB 2.0 Hub Controller
The Microchip USB2513B/M2 is a highly integrated 3-port USB 2.0 hub controller designed to provide a robust and flexible solution for expanding USB connectivity in a wide range of applications. Successful implementation of this IC requires careful attention to several key design areas to ensure optimal performance, reliability, and compliance with USB standards.
Power Configuration and Management
A primary design consideration is the power scheme. The hub supports three distinct modes: Bus-Powered, Self-Powered, and Compound modes. The choice profoundly impacts the available power for downstream ports. In Self-Powered mode, an external 5V power supply must be provided to the `VBUS` pins, capable of delivering sufficient current for all connected devices. Decoupling of this supply is critical; a 10µF bulk capacitor paired with 100nF ceramic capacitors placed close to the `VBUS` pins is essential to suppress noise and ensure stable operation. For bus-powered applications, the upstream port's current budget (typically 500mA for USB 2.0) must be allocated carefully between the hub's operation and its downstream ports.
Signal Integrity and PCB Layout
As a high-speed interface, preserving USB signal integrity is paramount. PCB layout must be treated as an RF design. The differential data pairs (DPx/DMx) must be routed with strict 90-ohm impedance control. Trace lengths should be matched to within 150 mils to minimize skew. The upstream port traces should be given priority, kept as short and direct as possible. It is strongly recommended to place the 24MHz crystal oscillator and its load capacitors (typically 22pF) extremely close to the XI and XO pins, with a solid ground plane beneath them to avoid noise injection. Routing other signal traces under or near the crystal should be avoided.
ESD Protection and Robustness
While the USB2513B/M2 incorporates some internal ESD protection, additional external ESD protection diodes on all downstream data and power lines are highly recommended for enhancing product durability. This is crucial for consumer-facing ports that are frequently hot-plugged. Components should be selected to meet IEC 61000-4-2 standards. A ferrite bead in series with the `VBUS` line for each downstream port can help suppress high-frequency noise from connected devices.
Configuration and Customization
The hub's default configuration is suitable for many applications, but its behavior can be customized via strapping options or an external Serial EEPROM (I²C). Pull-up or pull-down resistors on specific configuration pins (e.g., `SPEED`, `CFG[1:0]`) during reset allow hardware customization of parameters like battery charging support and port mapping. For full firmware-level customization, including custom Vendor ID (VID), Product ID (PID), and product strings, an EEPROM can be connected to the I²C bus (`SDA/SCL`). This is a powerful feature for branding and creating tailored functionality.
Thermal and Mechanical Considerations
Although the device is offered in a compact 36-pin QFN package with an exposed thermal pad, ensuring adequate heat dissipation is important. The PCB thermal pad must be properly soldered to a copper pour on the board, which should be connected to ground via multiple thermal vias. This practice efficiently transfers heat away from the IC, preventing thermal overload during sustained high-speed data transfers.
ICGOODFIND: The USB2513B/M2 is a versatile and reliable hub IC whose performance is heavily dependent on thoughtful design. By focusing on a clean power delivery network, a meticulous high-speed PCB layout, robust ESD protection, and correct configuration, designers can fully leverage its capabilities to create stable and compliant USB expansion solutions.
Keywords:
1. Signal Integrity
2. Power Management
3. PCB Layout
4. ESD Protection
5. Configuration
