Datasheet

LPC11U3X All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 2.2 — 11 March 2014 55 of 77
NXP Semiconductors
LPC11U3x
32-bit ARM Cortex-M0 microcontroller
For a bus-powered device, the VBUS signal does not need to be connected to the
USB_VBUS pin (see Figure 28
). The USB_CONNECT function can additionally be
connected as shown in Figure 27
to prevent the USB from timing out when there is a
significant delay between power-up and handling USB traffic.
Remark: When a bus-powered circuit as shown in Figure 28 is used, configure the
PIO0_3/USB_VBUS pin for GPIO (PIO0_3) in the IOCON block to ensure that the
USB_CONNECT
signal can still be controlled by software. For details on the soft-connect
feature, see the LPC11U3x user manual (Ref. 1
).
Remark: When a self-powered circuit is used without connecting VBUS, configure the
PIO0_3/USB_VBUS pin for GPIO (PIO0_3) and provide software that can detect the host
presence through some other mechanism before enabling USB_CONNECT
and the
soft-connect feature. Enabling the soft-connect without host presence will lead to USB
compliance failure.
Fig 28. USB interface on a bus-powered device
LPC1xxx
V
DD
R1
1.5 kΩ
aaa-010179
USB-B
connector
USB_DP
USB_DM
V
SS
R
S
= 33 Ω
R
S
= 33 Ω
REGULATOR
VBUS