AM3358: Question for USB2.0 HS disconnection envelope detector threshold

Hi Hong,

I have assigned your query to our expert. Since its a holiday in TII office and the team is excepted to return on Wednesday. Please expect a delay in response.

Apologies for the delay.

Best Regards,

Suren

Hello Hong,

Thank you for the query.

The USB interface is compliant with Universal Serial Bus Revision 2.0 Specification and the data sheet may not include any specifications.

Hong Pei Chen said:

So, we would also like to know if it is the case that it is the higher driving current in device and might have the signal amplitude over the threshold and cause USB disconnection issue.

We do not expect such issues. The USB interface are also tested for compliance. 

Could you provide some additional inputs if this is a general query or you are seeing some issues with the USB interface.

Regards,

Sreenivasa

Hi Screenivasa,

it is the issue we are seeing the USB connection issue in other platform but not AM3358. so we would like to learn if it would have the same concern in AM3358.

what we learn the issue root cause is that the device with higher driving current and connected to our unit would trigger the envelop detector threshold.

Thanks

Hello Hong,

Thank you.

Hong Pei Chen said:

it is the issue we are seeing the USB connection issue in other platform but not AM3358. so we would like to learn if it would have the same concern in AM3358.

Understand.

Hong Pei Chen said:

what we learn the issue root cause is that the device with higher driving current and connected to our unit would trigger the envelop detector threshold.

Not sure i understand. fully.

Regards,

Sreenivasa

Hi Screenivasa,

could we say it should be such the threshold or detect mechanism in AM3358 but would not know the level value precisely?

thanks.

Hello Hong,

Thank you

Hong Pei Chen said:

could we say it should be such the threshold or detect mechanism in AM3358

Sorry again, I am not sure if i understand what you meant here.

Regards,

Sreenivasa

Hi Sreenivasa,

I would like to add information about Hong Pei's question. From USB 2.0 spec, we learned high speed disconnect detection threshold is between 525~625mV and we want to know what's the precise voltage value that would make AM3358 disconnection and does the voltage value could be set by ourselves or it's a fixed default value.

Or AM3358 actually triggers the disconnection by detecting the current value exceeds the threshold.

Thanks,

Alex

Hello Alex,

Thank you. 

Yu-Cheng Chang said:

AM3358 actually triggers the disconnection by detecting the current value exceeds the threshold.

Refer below section in the TRM 

16.2.7 USB Controller Host and Peripheral Modes Operation

Yu-Cheng Chang said:

I would like to add information about Hong Pei's question. From USB 2.0 spec, we learned high speed disconnect detection threshold is between 525~625mV and we want to know what's the precise voltage value that would make AM3358 disconnection and does the voltage value could be set by ourselves or it's a fixed default value.

The range is provided to take care of the variations between devices, temperature or any other parameters.

This is handled by the USB controller.

You might want to read the USB2.0 specs if you are looking for the internal implementation details.

Please let me know if my understanding is correct or you have any other thoughts.

Regards,

Sreenivasa

Hi Sreenivasa,

Sorry for my typo. It's "Does AM3358 actually trigger the disconnection by detecting the current value exceeds the threshold?"

From USB 2.0 spec, "Signals with differential amplitudes > 625 mV must reliably activate the Disconnection Envelope Detector." We think whether the Disconnection will be triggered when the amplitude is between 525mV and 625mV depends on the setting value of AM3358. 

"The range is provided to take care of the variations between devices, temperature or any other parameters."--> So there is no a fixed value that triggers the Disconnection Envelope Detector of AM3358, right?

Thanks,

Alex

Hello Alex,

Thank you. 

Yu-Cheng Chang said:

"The range is provided to take care of the variations between devices, temperature or any other parameters."--> So there is no a fixed value that triggers the Disconnection Envelope Detector of AM3358, right?

The USB controller is designed to ensure that all the devices trip within the range specified in the USB standards.

If you question is there a fixed input value at which all the devices will trip - i guess the answer would be No.

Regards,

Sreenivasa