CY7C65640B/30/20 as a bus powered hub

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    Question: Can the CY7C65640B/30/20 be configured as a bus powered hub?



    Yes, with limitations. The CY7C65620 is a two port hub and without limitations can be used as a bus powered hub.  For the CY7C65640B and CY7C65630 limitations have to be imposed in a bus powered design because of the power available on any host port. A host port supplies only 500 mA. That means the amount of power the hub consumes restricts the number of down stream ports that can be used. With the CY7C65640B, the number of high-speed ports has to be restricted to two. This means that there is 300 mA for the hub and any ports that are not exposed. i.e. you can use one of the internal ports as a keyboard and create a keyboard hub with two exposed high speed ports. Depending on the power that keyboard uses there may be enough power for a second internal full/low speed device on the fourth port. Due to power consumption of the high speed ports, designs will not be able to use high speed on either of the two internal ports, just the two external ports.