UM11158
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© NXP B.V. 2018. All rights reserved.
User manual
Rev. 0.2 — 16 October 2018
14 of 20
NXP Semiconductors
UM11158
LPCXpresso55S69 Development Board
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 LPC55S69 (P10)
•
USB High Speed connector for LPC55S69 (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.
The LPC55S69 and most other circuitry on the board can be powered at 1.8V or 3.3V,
selected at jumper P4. Note that the MMA8652 Accelerometer and use of most SD cards
requires 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.
For further details, refer to the board schematics.
5.1 Measuring LPC55S69 supply current
A 2.43 ohm resistor (R91) is connected in series with the 3.3V supply to the LPC55S69
device, and the voltage drop across this can be measured at header P12, providing a
mechanism to measure current draw of the MCU using a voltmeter. The voltmeter positive
probe should be applied to P12 pin 1. Use Ohm's law to calculate the current (LPC55S69
current = measured voltage / 2.43). As an example, if the measured voltage is 10 mV,
then 10e-3 / 2.43 = 4.11 mA.
A current meter may be inserted at P11 to measure the LPC55S69 VDD input current
after first removing R92. Note that a jumper needs to be installed at P13 once R92 has
been removed in order for power reach the LPC55S69 target
6. Board serial connections
This section describes connections between LPC55S69 on-board serial peripherals and
connectors for use with off-board devices.
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