USB2.0 PHY IC
6.1
Driver Characteristics of Full-Speed Drivers in High-Speed
Capable Transceivers
The USB transceiver uses a differential output driver to drive the USB data signal onto the USB cable.
Figure 6.1 shows the V/I characteristics for a full-speed driver which is part of a high-speed capable
transceiver. The normalized V/I curve for the driver must fall entirely inside the shaded region. The
V/I region is bounded by the minimum driver impedance above (40.5 Ohm) and the maximum driver
impedance below (49.5 Ohm). The output voltage must be within 10mV of ground when no current is
flowing in or out of the pin.
Drive High
Iout
Slope = 1/49.5 Ohm
(mA)
-6.1 * |VOH|
Test Limit
Slope = 1/40.5 Ohm
-10.71 * |VOH|
0
0.566*VOH
0.698*VOH
VOH
0
Vout (Volts)
Figure 6.1 Full-Speed Driver VOH/IOH Characteristics for High-speed Capable Transceiver
Revision 1.3 (10-05-04)
SMSC GT3200, SMSC USB3250
DATA1S3HEET
SMSC [ SMSC CORPORATION ]
