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i.MX6S USB interface bring up

Question asked by Vinayakam Mani on Feb 10, 2015
Latest reply on Feb 10, 2015 by igorpadykov

Hi, we have a custom board based on i.MX6 Solo processor and working on bringing up USB interface. the  reference firmware we have is sabrelite board i.MX6Q  based and in Custom board, only HSB Host1 controller is used for the USB interface. Difference between the reference design and custom board is external USB hub is not used in custom. And in custom board, there is an additional component ( SRV05-4) used on DP and DM lines. Pin 1 of SRV05-4 chip is connected to DP and pin 6 is connected to DM and Vcc and Gnd to PIN no 5 and 6 respectively.

1)  Does this additional component brings any impact to differential impendence ( 90ohm) and processor pin voltage ( 400 mV) variations?  as per recommendations, the terminating resistor should not be altered? how we can over come this with out affecting the differential impedance and voltages?

2) The external hub has no dependency in firmware configuration as the ref board hub circuitry is self configured?