UM11158
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2022. All rights reserved.
User manual
Rev. 1.6 — 17 March 2022
15 of 24
NXP Semiconductors
UM11158
LPCXpresso55S69/55S28 Development Boards
5.2 Measuring LPC55Sxx device supply current
For further details, refer to the board schematics.Current supply to the LPC55Sxx Core
can be measured via P29 (supply into VDDA and the on-board DC-DC converter) by
removing R85. Supply current into the entire device (VDDA, DC-DC and I/O) can be
measured via P13 (removing R92), or by measuring the voltage drop across the 2.43 ohm
resistor (R91) which is accessible at P12.
6. Board serial connections
This section describes connections between LPC55Sxx on-board serial peripherals and
connectors for use with off-board devices.
6.1 LPC55Sxx USB Ports
The Board incorporates micro AB connectors for both of USB0 (Full Speed, connector
P10) and USB1 (High Speed, connector P9) ports of the LPCXpresso55S69. Both of
these ports are capable of operating as a device or a host, and this is why micro AB
connectors are used.
The Board can only be configured to support one of these ports as a host at a time (this is
a limitation of the board, not the LPC55Sxx). When either port is used as a host, power
must be supplied to the board via the +5V power only micro B USB port. Jumper J6 is
used to connect power from a load switch to the VBUS signal of the port selected; J6
should be placed in position 1-2 for USB1 or position 2-3 for USB0. If neither USB port is
being used as a USB host this jumper is not required.
Note that USB_VBUS1 pin is a 5V tolerant pin, so a resistor divider on the USB1_VBUS
pin is not required, but is installed on Revision A1 and A2 boards. These resistors may be
removed if VBUS detection issue is observed.
6.2 USART header
Header P8 is provided as a convenient way to use an LPC55Sxx USART with a serial to
USB cable. Flexcom 0 ports (P0_29 and P0_30) are used for this feature, since these
ports are assigned for USART ISP mode. Note that these ports are shared with the Link2
debug probe (LPC4322) and PMod connector; when using this header ensure that there
is no conflicting device connected to the PMod connector and that jumper P1 is installed
to disable the connection to the Link2. Always ensure the serial cable is only connected
when the board is powered to prevent the LPC55S69 being powered through this
TXD/RXD pins. Note that there is no level shifter between the LPC55Sxx target and this
header, so a UART to serial cable with voltage levels matching the setting of the P4 power
supply voltage selection jumper must be used.
NOTE: the silkscreen on the board is labeled from the perspective of a serial cable
connected to the board, so P8 pin 3 (labeled “RXD” on the board silkscreen) is connected
to PIO0_30 (Flexcomm0 TXD), and P8 pin 2 (labeled “TXD” on the board silkscreen) is
connected to PIO0_29 (Flexcomm0 RXD).
