In the Data Manual, we suggest "Connected to VUSB3P1 if not used" for USB ID pin.
What does it mean of "if not used"? Does it mean "USB" not used or "OTG" not used?
Why does it need to connect to VUSB3P1 in this case? Can't we keep it floating?
Thanks,
Antony
Hi Antony,
There is some detection on the ID pin :
- The default state is “ID high”. ID ground will be detected as a wake-up event (USB cable plug)
- ID being an high impedant node, keeping it unconnected may cause erroneous detections by noise coupling. Keeping ID high will avoid erroneous detections.
- ID detection is referenced to the VUSB3P1 regulator. The detection mechanism involves an internal pull-up to VUSB3P1. Hence the best choice for keeping it high is tying it to this supply
- Since ID is used for the OTG standard, it should be tied to VUSB3P1 if OTG is not used and hence also if USB is not used at all.
Keeping it floating is a risk. We have seen in the past erroneous detections triggered by noise coupling to this pin.
RegardsAnkit
Won't you risk false assertions (due to noise) in the case of OTG with no cable plugged as well, in case you say you will get them sometimes when OTG isn't used, and therefore recommends to pull the pin explicitly high? In my world this would mean that the internal pull-up isn't strong enough and requires an external pull-up in parallel as well to avoid any noise issues?
Thanks for clarifying Søren
Søren Steen Christensen - SSC Solutions ApS - Web: www.ssc-solutions.dk
Now the situation is, TPS65950 only acts as a device-B and no need to do any detection on ID pin.
In addition, sometimes we need to turn off VUSB3V1. If ID is externally pull-up to VUSB3V1, it would trigger an interrupt at the moment VUSB3V1 is turned off. (Because ID voltage drops.)
How can we overcome this?
Hi Soren
ID to be pulled to 3V1 supply only when USB and OTG are not used.
When ID is required (OTG is used) we have an internal pull-up to 3V1 and does not require any external pull-ups, so there will not be any false detection.
I hope it clarifies your doubt.
Regards
Ankit
Masking the ID_GND interrupt will prevent hte interrupt when ID voltage drops down.
Writing 1 to the following register bits, will mask the ID interrupt.
USB_INT_EN_FALL_CLR[4]
USB_INT_EN_RISE_CLR[4]
In addition to ID_GND interrupt, grounding ID would also trigger USB_PRES interrupt. But, we can't mask USB_PRES interrupt, since we still need it when VBUS becomes available.
So, it may still cause erroreous detection if ID internal pull-up is disabled and no external pull-up on ID?
Ankit Somani: ID to be pulled to 3V1 supply only when USB and OTG are not used. When ID is required (OTG is used) we have an internal pull-up to 3V1 and does not require any external pull-ups, so there will not be any false detection.
Hi Ankit,
Thanks for your answer. Just for my complete understanding. What you are saying is basically that "the internal pull-up is only active while operating in OTG mode". Correct? If this is the case, I agree that you would want to tie the pin externally somehow then not operating in OTG mode. But my assumption was, that you could have the internal pull-up active in non-OTG mode as well - Can't you do this?
Best regards and thanks again Søren
ALL CONTENT AND MATERIALS ON THIS SITE ARE PROVIDED "AS IS". TI AND ITS RESPECTIVE SUPPLIERS MAKE NO REPRESENTATIONS ABOUT THE SUITABILITY OF THESE MATERIALS FOR ANY PURPOSE AND DISCLAIM ALL WARRANTIES AND CONDITIONS WITH REGARD TO THESE MATERIALS, INCLUDING BUT NOT LIMITED TO, ALL IMPLIED WARRANTIES AND CONDITIONS OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT OF ANY THIRD PARTY INTELLECTUAL PROPERTY RIGHT. NO LICENSE, EITHER EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, IS GRANTED BY TI. USE OF THE INFORMATION ON THIS SITE MAY REQUIRE A LICENSE FROM A THIRD PARTY, OR A LICENSE FROM TI.
Content on this site may contain or be subject to specific guidelines or limitations on use. All postings and use of the content on this site are subject to the Terms of Use of the site; third parties using this content agree to abide by any limitations or guidelines and to comply with the Terms of Use of this site. TI and its suppliers reserve the right to make corrections, deletions, modifications, enhancements, improvements and other changes to the content and materials, its products, programs and services at any time or to move or discontinue any content, products, programs, or services without notice.