S6E2C2 Datasheet, PDF (191/207 Pages) Cypress Semiconductor – 32-bit ARM® Cortex®-M4F FM4 Microcontroller

S6E2C2 Series
*6: USB Full-speed connection is performed via twisted-pair cable shield with 90 Ω ± 15% characteristic impedance
(differential mode).
USB standard defines that the output impedance of the USB driver must be in the range from 28 Ω to 44 Ω.
So, a discrete series resistor (Rs) addition is defined in order to satisfy the above definition and keep balance.
When using this USB I/O, use it with 25 Ω to 30 Ω (recommended value 27 Ω) series resistor Rs.
28Ω to 44Ω Equiv. Imped.
28Ω to 44Ω Equiv. Imped.
Mount it as external resistance.
Rs series resistor 25Ω to 30Ω
Series resistor of 27Ω (recommendation value) must be added.
And, use "resistance with an uncertainty of 5% by E24 sequence.”
*7: They indicate rise time (TRISE) and fall time (TFALL) of the low-speed differential data signal.
They are defined by the time between 10% and 90% of the output signal voltage.
Rise time
Falling time
Note:
− See Low-Speed Load (Compliance Load) for conditions of external load.
Document Number: 002-05030 Rev.*A
Page 191 of 207