Is the capacitor on VBUS required?

Announcements

Live Webinar: USB-C adoption. Simple & Cost-efficient solutions | April 18th @9am or 5pm CEST. Register now !

Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
NiMc_4245981
Level 3
Level 3
10 replies posted 10 questions asked 5 replies posted

In the DataSheet for the CCG3 it shows a 10 μF capacitor on the VBUS line for DRP and DFP designs.  It is 1 μF for UFP.  I'm designing a DRP device and I find that when I'm sinking power, this 10 μF capacitance causes a 5 second delay if the power source is turned off and turned back on.  Can I reduce the size of this capacitor?

The VBUS_DISCHARGE pin doesn't seem to be able to discharge the capacitor below 1.8 V.  The two power sources I've tested won't provide 5V until the line drops to 0.8 V.

My last resort is to use a 10 kΩ resistor in parallel to the capacitor, but I would rather use a smaller capacitor.

0 Likes
1 Solution
NoriTan
Employee
Employee
25 sign-ins 5 questions asked 10 sign-ins

The USB-PD specification says "Source Bulk Capacitance" must be added to the VBUS.

GS004130.png

And the capacitance value is specified as follows.

GS004129.png

So, 10uF is required for DFP or power source.

I am referring "USB Power Delivery Specification Revision 2.0, Version 1.1"

Regards,

Noriaki

View solution in original post

0 Likes
3 Replies
NoriTan
Employee
Employee
25 sign-ins 5 questions asked 10 sign-ins

The USB-PD specification says "Source Bulk Capacitance" must be added to the VBUS.

GS004130.png

And the capacitance value is specified as follows.

GS004129.png

So, 10uF is required for DFP or power source.

I am referring "USB Power Delivery Specification Revision 2.0, Version 1.1"

Regards,

Noriaki

0 Likes
ShifangZ_26
Moderator
Moderator
Moderator
10 likes given 250 sign-ins 1000 replies posted

Hi,

Kindly refer below explain as per PD3.0 SPEC:

1. 10 μF capacitor on the VBUS line for DRP and DFP designs, USB Power Delivery Specification Revision 3.0, Version 1.2

pastedImage_0.png

2. The two power sources I've tested won't provide 5V until the line drops to 0.8 V.

pastedImage_1.png

Best Regards,

Lisa

0 Likes
NiMc_4245981
Level 3
Level 3
10 replies posted 10 questions asked 5 replies posted

I've decided leave the 10 μF in place and add a 33 kΩ resistor.  This is the largest resistance that can discharge the capacitor from 5 V to 0.8 V in tSafe0V (650 ms).

0 Likes