User manual

LPCXpresso Experiment Kit - User’s Guide
Page 25
Copyright 2013 © Embedded Artists AB
5 Powering Options
There are a couple of different options how to power the experiments. Below is a short list,
summarizing the options:
Controller
R2
Power option #1
Power via external +5V
supply (J1 or J17)
LPCXpresso board
Do not mount R2
Power via USB
connector on
LPCXpresso board
Yes, can also be done
LPC1114 in DIL28
Mount R2
-
Yes
mbed
Do not mount R2
Power via mbed USB
connector
Yes, can also be done
If the servo interface, USB Host interface and/or RF module are used the board MUST be powered
via an external +5V supply. Powering via the USB connectors of the LPCXpresso/mbed module is
typically not enough.
Below is a more details description. Read through all different options to determine which powering
option fits your needs.
 The simplest and most common way is to let the LPCXpresso board generate the +3.3V
supply that is needed. This voltage is available on pin 29 on the LPCXpresso expansion
connector (see schematic for details). R2 should not be mounted in this case.
- The LPCXpresso board can supply up to about 100 mA on the +3.3V supply.
Note that by turning on all LEDs and activating all features on the board it is possible
to consume more than 100 mA.
- Note that the voltage is not exactly 3.3V, but a Schottky diode forward voltage drop
less, so around 3.15V.
 In case the LPCXpresso board is not powered via its USB connector an external +5V DC
supply is needed. Connect the external supply to J1 or J17 (as described below).
- If the internal +3.3V voltage regulator on the LPCXpresso board is used, R2 shall not
be mounted. Else R2 shall be mounted (and U1 is the +3.3V regulator in use).
 If current consumption on the +3.3V supply is higher that the LPCXpresso board can provide
an external +5V DC supply is needed. This is typically true when working with wireless/RF
modules and/or with the USB Host interface (J10 connector). When working with servo
motors an external +5V supply is absolutely needed.
- An external +5V DC supply can connect to J1, which is a 2.1mm power jack with
positive center pin. Note that there is no overvoltage protection in the design. Make
sure that the connected power supply does not supply more than +5V DC. The
current capability of the external +5V DC supply should be in the region of 1-2
Ampere.
- Connector J17 (mini-B USB connector on the back side of the pcb) can also be used
to supply an external +5V DC supply via the USB Host port on a PC/laptop/USB hub.
 When using the LPC1114 in DIL28 package an external +5V DC supply is needed. Feed the
+5V via J1 or J17 (as described above) and mount R2 (in order to let U1 be the +3.3V
regulator in use).