MiniCom (OP6800) User's Manual

> ## Appendix C. Demonstration Board

> Appendix C describes the features and accessories of the Demonstration Board, and explains the use of the Demonstration Board to demonstrate the OP6800 and to build prototypes of your own circuits.

> ### C.1 Mechanical Dimensions and Layout

> Figure C-1 shows the mechanical dimensions and layout for the OP6800 Demonstration Board.

> Figure C-1. OP6800 Demonstration Board Dimensions

> Table C-1 lists the electrical, mechanical, and environmental specifications for the Demonstration Board.

> Table C-1. Demonstration Board Specifications
> Parameter | Specification
> Board Size | 3.40" × 4.20" × 1.19" (87 mm × 107 mm × 30 mm)
> Operating Temperature | -40°C to +70°C
> Humidity | 5% to 95%, noncondensing
> Input Voltage | 7.5 V to 25 V DC
> Maximum Current Draw (including user-added circuits) | 140 mA at 12 V and 25°C, 100 mA at 12 V and 70ºC
> Prototyping Area | 1.7" × 2.1" (43 mm × 53 mm) through hole, 0.1" spacing
> Standoffs/Spacers | 4, accept 4-40 x 11/8 screws

> ### C.2 Power Supply

> The OP6800 requires an unregulated +RAW power input of 9 V to 36 V DC, which can be supplied from the Demonstration Board through the ribbon cable connection. The OP6800 has its own switching voltage regulator.

> Figure C-2 shows the distribution of the +RAW input power to the OP6800 through the Demonstration Board. The reference grounds on the OP6800, GND, and on the Demonstration Board, 0 V, are tied together at one connection point only to avoid creating a ground loop, which could lead to considerable electromagnetic interference.

> Figure C-2. Power Distribution to OP6800 and Demonstration Board

> The Demonstration Board has an onboard LM7805 linear regulator for the circuits on the Demonstration Board only. Its major drawback is its inefficiency, which is directly proportional to the voltage drop across it. The voltage drop creates heat and wastes power.

> You may wish to use a switching power supply in your applications where better efficiency is desirable. The LM2575 is an example of an easy-to-use switching voltage regulator. This part greatly reduces the heat dissipation of the regulator. The drawback in using a switching voltage regulator is its higher cost.

> Figure C-3. Demonstration 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.

> Be careful to limit the current draw in any prototype circuits you build on the prototyping area of the Demonstration Board to avoid operating the linear regulator outside its recommended limits. The LEDs and buzzer together can draw up to 70 mA, which still leaves some current capacity for your own circuits (see Table C-1) if you plan to use them with the LEDs and the buzzer.

> If you need additional current from the linear regulator beyond that specified in Table C-1, consider adding a heat sink to the linear regulator (remember to use silicone grease between the tab and the heat sink), or use a lower voltage power supply.

> ### C.3 Using the Demonstration Board

> The Demonstration 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 OP6800 right out of the box without any modifications to either board. There are no jumpers or dip switches to configure or misconfigure on the Demonstration Board so that the initial setup is very straightforward.

> The Demonstration Board comes with the basic components necessary to demonstrate the operation of the OP6800. Four LEDs (DS1-DS4) are connected to OUT07-OUT10, and four switches (S1-S4) are connected to IN00-IN03 to demonstrate the interface to the OP6800.

> The Demonstration Board has a buzzer that is normally off. The buzzer can be enabled to be on by setting the jumper across pins 1-2 on header JP1 on the Demonstration Board as shown in Figure C-4. When enabled on, the buzzer will sound whenever the OUT0 digital output on the OP6800 is on.

> Figure C-4. Demonstration Board Header JP1
> (Buzzer On/Off)

> The Demonstration Board provides the user with OP6800 connection points brought out conveniently to labeled points at headers J4, J5, J6, and J8 on the Demonstration Board. Small to medium circuits can be prototyped using point-to-point wiring with 20 to 30 AWG wire on the prototyping area. The holes are spaced at 0.1" (2.5 mm). The pinouts for headers J4, J5, J6, and J8 are shown in Figure C-5.

> Figure C-5. OP6800 Demonstration Board Pinout

> The Demonstration Board can then be rotated and mounted behind the OP6800 as shown in Figure C-6 to allow the Demonstration Board and the OP6800 to be used together.

> Figure C-6. Mounting Demonstration Board on OP6800

> NOTE | Remove the standoffs behind the OP6800 before attempting to mount the Demonstration Board.

> The OP6800 may also be panel-mounted with the Demonstration Board attached. Follow the instructions in Chapter 6, "Installation and Mounting Guidelines." Use 4-40 screws that are l 3/16" (plus the thickness of the panel) in length. Note that the Demonstration Board and the OP6800 end up on opposite sides of the panel as shown in Figure C-7.

> Figure C-7. OP6800 with Demonstration Board Mounted in Panel (rear view)

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