HX3 improves USB 2.0 signal quality similar to the SuperSpeed PHY to USB 2.0 PHY in the HX3 which is equally adjustable. There are four levels of transmit amplitude adjustment on the USB 2.0 PHY to increase eye height. In addition - the high-speed slope (which is to slew rate on the eye-opening) is also adjustable. The high-speed eye diagram on the left is a HX3 downstream port with the default PHY settings. The 410 mVs eye height meets USB specification with a minimum of 350 mV. However, the low high-speed slope closes the eye-opening, removing the margins for passing USB compliance by adjusting both transmit amplitude and high-speed slope. The resulting eye height is increased to 550 mv with a steeper high-speed slope making the passing of USB compliance less challenging.