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MicroController Pros Corporation
PIC-P40-28 User Manual 6/ 12 February 2008
3.2. Power Supply Requirements
Power input to the board is supplied via a barrel connector with 5.5mm outer and 2.5mm inner diameter.
An on-board bridge rectifier provides polarity reversal protection and allows you to use both AC or DC
input voltages.
An on-board LM317 adjustable output voltage regulator can be set via a jumper to provide the board with
either 5.0V or 3.3V DC operating voltage. In the open position of jumper 3.3V, the output voltage is 5.0V.
In the jumper-closed position, the output voltage is 3.3V
Jumper 3.3V Board Operating Voltage (BOV)
Open 5.0V DC
Closed 3.3V DC
The input voltage supplied to the board should be at least 3.5V above the desired board operating voltage
(BOV) if you use a DC power supply, and 2.5V above BOV if you use an AC power supply.
5.0V Board Operating Voltage 3.3V Board Operation Voltage
Minimum AC input voltage 7.5V AC 5.8V AC
Minimum DC input voltage 8.5V DC 6.8V DC
The following maximum input voltages should not be exceeded by your power supply, otherwise you risk
damaging the board:
Maximum AC input voltage 10.5V AC
Maximum DC input voltage 15V DC
The current rating of your power supply is uncritical, as this board requires less than 100mA to operate.
Therefore, any power supply with a current rating of 100mA or higher can be used. A higher current rating
is not a problem, as the board will only draw as much current from the supply as is needed for operation.
In general, you should use voltages close to the minimum required input voltage. It reduces stress on the
voltage regulator, as a smaller voltage differential has to be dissipated into heat.
A word of caution, however: Many cheap transformer-based wall-plug power supplies provide an
unregulated output voltage that under no load is usually much higher than the rated output voltage printed
on the supply. This high output voltage then “collapses” under load and can be lower than the rated
output voltage. To avoid damage to your board, verify with a multi-meter that the true voltage of your
power supply is within the above stated limits before connecting it to this board.
3.3. 28- and 40-pin MCU sockets
Caution: Only populate one socket at a time. Do not insert microcontrollers into more than one socket
at a time, or you may damage the microcontroller chips.
Caution: Check the pin orientation of the sockets before inserting a chip. The 28- pin socket is
rotated by 180 degrees in relation to the 40-pin socket (see ). This means that the pin 1
location for the 28-pin socket is in the lower right hand corner, whereas the pin 1 position for the 40-pin
socket is in the upper left hand corner of the socket. Make sure you align pin 1 of your microcontroller
with pin 1 of the socket. Inserting a microcontroller chip incorrectly can damage it.
Figure 3-1
