UM11158
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User manual
Rev. 1.6 — 17 March 2022
14 of 24
NXP Semiconductors
UM11158
LPCXpresso55S69/55S28 Development Boards
5. Board
Power
The LPCXpresso55S69 board re5V input to power the on-board voltage low
dropout linear regulators, of which there are 3, all available from Torex Semiconductor.
The Link2 Debug probe has a 2.5V regulator (U10) which draws power from USB
connector P6 (“Debug Link”) only. The Debug Probe is unpowered if P6 is unconnected.
There are two other regulators, providing the option of 1.8V (U8) or 3.3V (U9) to the other
devices on the board; these regulators can be powered by any of the following (+5V)
sources:
•
USB +5V Power only connector (P5)
•
USB Full Speed connector for LPC55Sxx (P10)
•
USB High Speed connector for LPC55Sxx (P9)
•
USB Debug Link connector (P6)
The +5V sources above are connected via protection diodes to prevent reverse powering
of any of them by another source. The +5V output of these combined sources is also
connected to the Arduino and Mikroe expansion sites. Note that if P9 or P10 is configured
as a USB host port then those connectors will not supply power to the board and another
source must be provided.
5.1 1.8V operation
LPCXpresso55S69 Revision A1 boards (with LPC55S69 revision 0A silicon) require a
minimum supply voltage of 1.85V, so jumper P4 must be set in the 3.3V position, or an
external supply provided to the center pin of P4.
For Revision A2 boards, P4 may be set in the 1.8V position, however note that this is the
minimum voltage supply for the LPC55Sxx devices, so variations in the 1.8V regulator
tolerance and/or loading on the regulator may cause the brown-out detect (BOD) to
trigger, especially when using the device at higher operating frequencies (when current
draw is higher). The default BOD settings may be changed to avoid this problem, before
higher clock speeds and/or higher current draw I/Os are enabled (e.g. at the start of
main()) with a function call to the power library, as shown below:
POWER_SetBodVbatLevel(
kPOWER_BodVbatLevel1650mv
,
kPOWER_BodHystLevel50mv
, false);
It should be noted that this workaround may not work in all cases due to the regulator
used on Revision A2 boards having a tolerance that does not guarantee the minimum
required voltage output; see
Note that the MMA8652 Accelerometer and use of most SD cards require the board to be
configured for 3.3V operation. The power connection to the Accelerometer may be
disconnected by removing R20; installing header P25 provides a convenient way to
connect/disconnect this.
Note that the forward drop voltage of the green and blue user LEDs (which are driven
directly from GPIOs of the LED device) is too high for these to operate when the board is
configured for 1.8V operation
For further details, refer to the board schematics.
