AnsweredAssumed Answered

Re: QN9080 DK board: Confirm QN9080 USB I/F work well when Vcc=1.8V for on-board QN9080

Question asked by Estephania Martinez Employee on Feb 6, 2019
Latest reply on Jun 13, 2019 by Estephania Martinez
Branched from an earlier discussion

Hello, 

 

 

The USB module can work at 1.8V, but the problem is that the data lines at this voltage level are out of the USB electrical specification, so the USB host may not be able to communicate properly.

 

The electrical specification of USB is described in Table 7-7. DC Electrical Characteristics of the USB 2.0 specification and it can be downloaded from USB.org . The important parameters impacting this are: 

 

Output Levels for Full-speed

High (driven) – VOH - 2.8V-3.6V

Input levels for Full-speed

High (driven) – VIH – 2.0V

 

This means that the USB receiver could operate at 2V minimum but the output high level should be between 2.8-3.6V to meet the specification.

 

Unfortunately, there is no way to separate the USB I/O voltages from the rest of the I/O pins without the use of an external level translator.

 

Regards, 

Estephania 

Outcomes