Datasheet

LPC1759_58_56_54_52_51 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 8.5 — 24 June 2014 64 of 80
NXP Semiconductors
LPC1759/58/56/54/52/51
32-bit ARM Cortex-M3 microcontroller
15. Application information
15.1 Suggested USB interface solutions
If the LPC1759/58/56/54/52/51 V
DD
is always greater than 0 V while V
BUS
= 5 V, the V
BUS
pin can be connected directly to the V
BUS
pin on the USB connector.
This applies to bus powered devices where the USB cable supplies the system power. For
systems where V
DD
can be 0 V and V
BUS
is directly applied to the V
BUS
pin, precautions
must be taken to reduce the voltage to below 3.6 V.
The maximum allowable voltage on the V
BUS
pin is 3.6 V. One method is to use a voltage
divider to connect the V
BUS
pin to the V
BUS
on the USB connector.
The voltage divider ratio should be such that the V
BUS
pin will be greater than 0.7V
DD
to
indicate a logic HIGH while below the 3.6 V allowable maximum voltage.
Use the following operating conditions:
VBUS
max
= 5.25 V
V
DD
= 3.6 V
The voltage divider would need to provide a reduction of 3.6 V/5.25 V or ~0.686 V.
Fig 28. LPC1759/58/56/54/52/51 USB interface on a bus-powered device
LPC17xx
V
DD(3V3)
R1
1.5 kΩ
R2
USB_UP_LED
002aad940
USB-B
connector
USB_D+
USB_D−
V
BUS
V
SS
R
S
= 33 Ω
R
S
= 33 Ω