Fujitsu MB91401 manual USB interface, Prelminary, 2004.11.12, Parameter, Symbol, Unit, Remarks

MB91401								Prelminary
								2004.11.12
	(9) USB interface
	Parameter	Symbol	Pin		Value		Unit	Remarks
				Min	Typ	Max
	Input clock	tucyc	UCLK48		48*1		MHz	2500ppm accuracy*1
	RISE Time	tutfr	UDP, UDM	4		20	ns	*2
	Fall Time	tutff	UDP, UDM	4		20	ns	*2
	Differential Rise and Fall	tutfrfm	UDP, UDM	90		111.11	%	*2
	Timing Matching
	Driver Output Resistance	tzdrv	UDP, UDM	28		44	Ω	*3
				tucyc
	UCLK48

UDP

90% 90%

10%

UDM

tutfr

10%

tutff

*1 : The AC characteristics of the USB interface conform to USB Specification Revision 1.1.

*2 : <Driver Characteristics TFR, TFF, TFRFM>

These items specify the differential data signal rise (trise) and fall (tfall) times. These are defined as the times between 10% to 90% of the output signal voltage.

For the full-speed buffer, trise and tfall are specified such that the tr/tf ratio falls within ± 10% to minimize RFI radiation.

*3 : <Driver Characteristics ZDRV>

USB full-speed connection is performed via a shielded twisted-pair cable at a characteristic impedance of 90 Ω ± 15%. The USB Standard stipulates that the USB driver’s output impedance must be within the range of 28 Ω to 44Ω. The USB Standard also stipulates that a discrete serial resistor (RS) must be added to have balance while satisfying the above standard.

The output impedance of the USB I/O buffer on this LSI is about 3 Ω to 19 Ω. Serial resistor RS to be added must be 25 Ω to 30 Ω (27 Ω recommended) .

Capacitor CL of 50 pF must be added as well.

64