66AK2G12: USB VBUS input

Naoki Kawada

Guru 19890 points

Part Number: 66AK2G12

Hi,

My customer has a question about USB VBUS input. This is analog power input pin to sense and validate the VBUS line but is this mandatory input for USB nominal operation even if USB is in any operating mode? My understanding is it is mandatory (I`m not exactly sure but i believe the internal phy must monitor the input to handle VBUS error). Just in case, please let me know if it is correct or not.

Best Regards,
NK

over 6 years ago

0 Stanislav Stilyanov over 6 years ago

TI__Genius 17770 points

Hi Naoki Kawada,

Not sure I fully understand your question. Sorry for that.

VBUS sense pin does need to be connected to VBUS in all, host, device, and DRD modes. I can see from the datasheet that it is 5-V tolerant, but max voltage is 5.25V. Because of this, you will need a voltage clamping for example for 5.1 Volts.

Regards,

Stan

0 Yordan Kovachev over 6 years ago

TI__Guru**** 161600 points

Hi,

USB VBUS should be connected as described in the 66AK2Gx Schematic Checklist:
www.ti.com/.../sprac54a.pdf

See section 2.15USB. To answer your question, you should connect the VBUS pin.

Best Regards,
Yordan

0 Naoki Kawada over 6 years ago in reply to Yordan Kovachev

Guru 19890 points

Hi Yodan, Stan,

Thanks for your quick reply. Sorry, it seems my question was not clear but your replies answered to our question.

Can i ask one more thing ?
They have DVDD33_USB powered properly in their custom board. My customer is wondering why USB DP/DM (and other USB signals) have "DVDD18 / DVDD33_USB" at POWER column in Table 4-1. Pin Attributes (continued) of datasheet. Not sure why DVDD18 has been shown here. Do you have any comment on this ?

Best Regards,
NK

0 Stanislav Stilyanov over 6 years ago in reply to Naoki Kawada

TI__Genius 17770 points

I got feedback from datasheet team. This is correct, both supplies must be present for USB.
I think it is because some part of USB PHY is powered by 3.3V and other by 1.8V.

Regards,
Stan

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66AK2G12: USB VBUS input