A stand-alone USB driver with internal and external series resistors for impedance matching

摘要

A USB driver (figure 3) using two parallel MOS transistors 38 and 42 for impedance and curvature control may be adapted for standalone USB1.1 operation by connecting the gates of the transistors to Vdd, bypassing most of the on-chip resistor 22 by a metal strap, and adding a precision off-chip resistor 206. The remaining portion of the on-chip resistor gives ESD protection.