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MB91401
64
(9) USB interface
*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 (R
S) 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 R
S to be added
must be 25 Ω to 30 Ω (27 Ω recommended) .
Capacitor CL of 50 pF must be added as well.
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
Timing Matching
tutfrfm UDP, UDM 90 111.11 % *2
Driver Output Resistance tzdrv UDP, UDM 28 44 Ω *3
UCLK48
tucyc
10% 10%
90% 90%
tutfftutfr
UDP
UDM
Prelminary
2004.11.12