NXP Semiconductors
UM10855
LPCXpresso board for LPC54100 family of MCUs
UM10855_OM1377.docm
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© NXP B.V. 2014. All rights reserved.
User manual
Rev. 1.0
— 4th November 2014
9 of 19
5. Board power connections & measurement
The LPCXpresso54102 board re5V input to power the on-board voltage
regulators which in turn power the Link2 debug probe and other +3.3V circuits, the
LPC54102 target and other +1.8V circuits, and the A5V and +3.3V power rails.
When the main external power source is from the Link2 side USB micro B-type connector
(J6), both the Link side and LPC54102 Target sections of the board are powered. When
the main external power is from the Target side USB micro B-type connector (J4), header
P3, or FTDI header (J5) only the LPC54102 Target section of the board is powered.
A block diagram of the board power tree is shown in
Figure 3. When the LPC54102
Target is to be debugged from an external debug probe, instead of the on-board Link2
debug probe, the Link USB connector (J6) must be disconnected. The circle with I
indicates a current monitor chip. Note that the LPC54102 does not provide a USB
interface, the Target USB connector J4 is for power only. The LPC54102 Target VDD
selection of 1.8V or 3.3V is made at JP7, with 3.3V set as the default.
SWD
Dual
Supply
Voltage
buffer
Link
+2.5V
LDO (U19)
Target
+3.3V
LDO (U18)
Arduino
connector
Bridge
SPI / I2C
Link USB
Micro-B
(J6)
Target
External
+5V
Micro-B
(J4)
Vbus
External_VIN
P3
Link section
of board
FTDI
Header
(J5)
+5V
LPC54102
Tri-color
LED
Target
+1.8V
LDO (U17)
Target section
of board
+2.5V
I
VDD_NIOBE
VDD_NIOBE
JP7
+5V
+3.3V
Figure 3 - Board Power block diagram
5.1
LPCXpresso54102 current measurement
The LPC54102 current can be measured by measuring the voltage across a sense
resistor in series with the supply, a current meter or using the on board current
measurement circuit. Each of these methods will be described in subsections below.
There is no current monitoring of the Link section circuits on the board. The Target side
power going to LEDs and support ICs is not monitored by the current measurement
circuit. The LPC54102 LQFP package has the core and IO power both sourced from the
same VDD pins.
When a shield board, such as the Sensor Shield Board in the Sensor Processing/Motion
Solution (OM13078) is attached, attempting to measure the lowest possible power the
LPC54102 IO pins must be configured according to how the software has configured the
sensors on the Sensor shield board to ensure there is no extra current from the
LPC54102 IO ports that have external pull-up or pull-down resistors enabled. JS17
should be opened to ensure no leakage through the tri-color LED and +3.3V supply.