The article delves into the intricacies of USB 2.0, a widely used communication standard that differs significantly from USB 3.0. USB 2.0, characterized by its full-duplex pseudo-differential bus and lack of AC coupling, presents challenges in terms of galvanic isolation compared to its successor, USB 3.0. However, incorporating USB 2.0 into projects is relatively straightforward, with the use of USB hubs being a popular method.
USB 2.0 hubs, which are now ubiquitous, offer a cost-effective solution with a plethora of options available. The standard 4-port hubs, featuring one uplink port to the host and four downlink ports to devices, are commonly used. While there are 7-port hub options available, it is important to scrutinize the datasheet as some may consist of two 4-port chips in a single package, potentially causing bottlenecks.
When it comes to recommendations for hub ICs, SL2.1 chips are favored for their ease of use and hand-soldering capabilities. Additionally, Western-origin chips from companies like Texas Instruments are renowned for their quality. To ensure a steady supply of hub ICs, leaving zero-ohm footprints under the hub’s package can be a preemptive measure.
Powering USB 2.0 hub ICs is relatively simple, as most include a 5V to 3.3V linear regulator. It is also possible to power hub ICs directly from a 3.3V source with the appropriate configuration. Adding capacitors to the power pins of hub ICs is advisable to enhance stability.
In terms of protection, ESD diodes are essential in safeguarding USB ports from potential harm caused by static electricity. The article elaborates on a personal experience involving the implementation of ESD diodes to resolve a reboot issue with a Pi Zero device connected to a USB soundcard.
Furthermore, over-current control switches, such as the SY6820, are recommended to prevent system reboots in the event of a short-circuit. These switches also enable the convenient on and off switching of port power.
In conclusion, the article provides valuable insights and recommendations regarding the usage of USB 2.0 hubs and connectors, aiming to assist individuals in optimizing their projects. By addressing key considerations such as power supply, protection measures, and component selection, users can enhance the reliability and functionality of their USB 2.0 setups.