MB9B320TA Datasheet, PDF (124/141 Pages) SPANSION – This document states the current technical specifications regarding

DataSheet
*6 : USB Full-speed connection is performed via twist pair cable shield with 90Ω ± 15% characteristic
impedance (Differential Mode).
USB standard defines that output impedance of USB driver must be in range from 28Ω to 44Ω. So, 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 25Ω to 30Ω (recommendation value 27Ω) Series resistor Rs.
28Ω to 44Ω Equiv. Imped.
28Ω to 44Ω Equiv. Imped.
Mount it as external resistor.
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 rising time (Trise) and falling time (Tfall) of the low-speed differential data signal.
They are defined by the time between 10% and 90% of the output signal voltage.
Rising time
Falling time
See "・Low-Speed Load (Compliance Load)" for conditions of the external load.
January 30, 2015, MB9B320TA_DS706-00062-2v0-E
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