LPC5411x All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2018. All rights reserved.
Product data sheet Rev. 2.1 — 9 May 2018 92 of 105
NXP Semiconductors
LPC5411x
32-bit ARM Cortex-M4/M0+ microcontroller
The internal pull-up (1.5 k) can be enabled by setting the DCON bit in the
DEVCMDSTAT register to prevent the USB from timing out when there is a significant
delay between power-up and handling USB traffic. External circuitry is not required.
Fig 34. USB interface on a self-powered device where USB_VBUS = 5 V
LPCxxxx
V
DD
R1
1.5 kΩ
aaa-023996
USB-B
connector
USB_DP
USB_DM
USB_VBUS
V
SS
R
S
= 33 Ω
R
S
= 33 Ω
USB
R2
R3
D+
D-
Two options exist for connecting VBUS to the USB_VBUS pin:
(1) Connect the regulator output to USB_VBUS. In this case, the USB_VBUS signal is HIGH whenever the part is powered.
(2) Connect the VBUS signal directly from the connector to the USB_VBUS pin. In this case, 5 V are applied to the USB_VBUS pin
while the regulator is ramping up to supply V
DD
. Since the USB_VBUS pin is only 5 V tolerant when V
DD
is at operating level,
this connection can degrade the performance of the part over its lifetime. Simulation shows that lifetime is reduced to 15 years
at T
amb
= 45 °C and 8 years at T
amb
= 55 °C assuming that USB_VBUS = 5 V is applied continuously while V
DD
= 0 V.
Fig 35. USB interface on a bus-powered device
REGULATOR
VBUS
LPCxxxx
V
DD
R1
1.5 kΩ
aaa-023997
USB-B
connector
USB_DP
USB_DM
V
SS
USB_VBUS
(2)
USB_VBUS
(1)
USB
D-
R
S
= 33 Ω
R
S
= 33 Ω
D+
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