Power Supply; Using The Prototyping Board - Rabbit RabbitCore RCM2200 User Manual

B.3 Power Supply
The RCM2200 requires a regulated 5 V ± 0.25 V DC power source to operate. Depending
on the amount of current required by the application, different regulators can be used to
supply this voltage.
The Prototyping Board has an onboard 7805 or equivalent linear regulator that is easy to
use. Its major drawback is its inefficiency, which is directly proportional to the voltage
drop across it. The voltage drop creates heat and wastes power.
A switching power supply may be used in applications where better efficiency is desir-
able. The LM2575 is an example of an easy-to-use switcher. This part greatly reduces the
heat dissipation of the regulator. The drawback in using a switcher is the increased cost.
The Prototyping Board itself is protected against reverse polarity by a Shottky diode at D2
as shown in Figure B-3.
J5
B.4 Using the Prototyping Board
The Prototyping Board is actually both a demonstration board and a prototyping board. As
a demonstration board, it can be used to demonstrate the functionality of the RCM2200
right out of the box without any modifications to either board. There are no jumpers or dip
switches to configure or misconfigure on the Prototyping Board so that the initial setup is
very straightforward.
The Prototyping Board comes with the basic components necessary to demonstrate the
operation of the RCM2200. Two LEDs (DS2 and DS3) are connected to PE1 and PE7, and
two switches (S2 and S3) are connected to PB2 and PB3 to demonstrate the interface to
the Rabbit 2000 microprocessor. Reset switch S1 is the hardware reset for the RCM2200.
66
1
D2
DCIN
+RAW
2
1N5819
3
C1
10 mF
Figure B-3. Prototyping Board Power Supply
LINEAR POWER SUPPLY
Vcc
7805
U1
3
1
C2
2
100 nF
RabbitCore RCM2200