User`s manual

User’s Manual 37

B.2 Power Supply

The RabbitCore 2000 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-2.

Figure B-2. 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.

B.3 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

Rabbit-

Core 2000

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 RabbitCore 2000. Two LEDs (DS2 and DS3) are connected to PA0 and

PA1, 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

RabbitCore 2000.

To maximize the availability of RabbitCore 2000 resources, the demonstration hardware

(LEDs and switches) on the Prototyping Board may be disconnected. This is done by cut-

ting the traces below the silk-screen outline of header JP1 on the bottom side of the Proto-

LINEAR POWER SUPPLY

POWER

10 µF

100 nF

7805

+RAW

DCIN

Vcc

1N5819