LPC540xx
NXP Semiconductors
32-bit ARM Cortex-M4 microcontroller
LPCxxxx
V
DD
R2
R3
R1
1.5 kꢁ
USB
USB_VBUS
D+
D-
USB-B
connector
R
R
= 33 ꢁ
= 33 ꢁ
S
S
USB_DP
USB_DM
V
SS
aaa-023996
Fig 49. USB interface on a self-powered device where USB_VBUS = 5 V
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.
LPCxxxx
V
DD
REGULATOR
(1)
(2)
USB_VBUS
USB_VBUS
USB
R1
1.5 kꢁ
VBUS
D+
USB-B
R
= 33 ꢁ
= 33 ꢁ
S
S
USB_DP
D-
connector
R
USB_DM
V
SS
aaa-023997
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 VDD. Since the USB_VBUS pin is only 5 V tolerant when VDD 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 Tamb = 45 °C and 8 years at Tamb = 55 °C assuming that USB_VBUS = 5 V is applied continuously while VDD = 0 V.
Fig 50. USB interface on a bus-powered device
LPC540xx
All information provided in this document is subject to legal disclaimers.
© NXP Semiconductors N.V. 2018. All rights reserved.
Product data sheet
Rev. 1.8 — 22 June 2018
153 of 168
NXP [ NXP ]
