Register Descriptions
1369
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
M3 Universal Serial Bus (USB) Controller
18.5.55 USB VBUS Droop Control Register (USBVDC), offset 0x430
The USB VBUS droop control 32-bit register (USBVDC) enables a controlled masking of VBUS to
compensate for any in-rush current by a Device that is connected to the Host controller. The in-rush
current can cause VBUS to droop, causing the USB controller's behavior to be unexpected. The USB Host
controller allows VBUS to fall lower than the VBUS Valid level (4.75 V) but not below AValid (2.0 V) for 65
microseconds without signaling a VBUSERR interrupt in the controller. Without this, any glitch on VBUS
would force the USB Host controller to remove power from VBUS and then re-enumerate the Device.
Mode(s):
OTG A or Host
USBVDC is shown in
and described in
Figure 18-66. USB VBUS Droop Control Register (USBVDC)
31
0
Reserved
VBDEN
R-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 18-71. USB VBUS Droop Control Register (USBVDC) Field Descriptions
Bit
Field
Value
Description
31-1
Reserved
0
Reserved. Reset is 0x0000.000.
0
VBDEN
VBUS Droop Enable
0
No effect
1
Any changes from VBUSVALID are masked when VBUS goes below 4.75 V but not lower than 2.0 V for
65 microseconds. During this time, the VBUS state indicates VBUSVALID.