User`s manual

User’s Manual 57
B.3 Power Supply
The RCM2000 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 LM340-T5 or equivalent. The LM340-T5 is an
inexpensive 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.
Figure B-3. Prototyping Board Power Supply
Capacitor C1 provides surge current protection for the voltage regulator, and allows the
external power supply to be located some distance away.
LINEAR POWER SUPPLY
POWER
IN
J1
100 nF
7805
U1
+RAW
DCIN
Vcc
C2
C1
1
2
3
1
2
3
1N5819
D2