UM11083
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© NXP B.V. 2018. All rights reserved.
User Manual
Rev. 1.1 — 24 September 2018
10 of 16
NXP Semiconductors
LPCXpresso804
User Manual
6. Power supplies and supply current measurement
This section describes available power options for the board, and how current
consumption of the LPC804 can be measured.
6.1 Board powering options
The Board may be powered by the USB connector (CN2), via the Arduino connector (5V
input pin) or by a coin cell battery inserted into the holder on the underside of the board.
When using the coin cell battery switch S4 must be closed to connect the battery.
Protection diodes are provided to prevent any of the possible power sources from back
powering another. Note that the LPC11U3x debug probe can only be powered by USB.
The LPC804 is powered from either a 1.8V or 3.3V (default) regulator, the selection of the
voltage used is made using JP8. The remaining circuitry on the board is always powered
by the 3.3V regulator, with the LPC11U3x debug probe having its own 3.3V regulator.
6.2 LPC804 supply current measurement
JP5 is provided as an insertion point for an ammeter to measure current flow to that MCU.
This jumper is inserted in line between the center pin of JP8 and the VDD supply of the
LPC804. When an ammeter is not being used, a jumper should be installed on JP5.
7. Other board features
This section describes other board features not detailed elsewhere in this document.
7.1 ISP booting and the ISP button
The LPC804 can be forced into ISP boot mode by holding down the ISP button (S2) and
then holding and releasing the Reset button (S3). The ISP button is connected to LPC804
pin PIO0_12, which is also routed to the Arduino expansion connector and to the cathode
of the green user LED3. LPC804 pin PIO0_12 can be reconfigured by software so that the
button can be used by an application as a general purpose button (refer to the LPC804
User Manual).
7.2 User button
The User button (S1) is for general purpose use by LPC804 applications. It is connected
to a 10K ohm pullup to 3.3V, and to the LPC804 PIO0_13 pin. It is also shared with the red
User LED1.
7.3 User LEDs
Three users LEDs are provided on the board, one blue, one green and one red. The
anodes of the LEDs are connected together, then through a zero ohm resistor to the 3.3V
regulator output (each has its own current limit resistor in-line). Each LED has a jumper in
series with it (JP21, JP22 and JP25) to prevent leakage from the LPC804 pins through the
diodes if accurate power measurement measurements are being performed. All the PIOs
used for these LEDs are also shared with the Arduino expansion connector, but those
connections to the expansion connectors are not routed via the jumpers. The LEDs are
connected to the LPC804 as shown in the table below.
