EVAL-AD421EB Analog Devices Inc, EVAL-AD421EB Datasheet

EVAL-AD421EB

Manufacturer Part Number

EVAL-AD421EB

Description

BOARD EVAL FOR AD421

Manufacturer

Analog Devices Inc

Datasheets

1.EVAL-AD421EB.pdf (14 pages)

2.EVAL-AD421EB.pdf (7 pages)

Specifications of EVAL-AD421EB

Rohs Status

RoHS non-compliant

Module/board Type

Evaluation Board

For Use With/related Products

AD421

Lead Free Status / RoHS Status

Not Compliant

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INTRODUCTION

This Application Note describes the evaluation board for the

AD421, loop powered 4-20mA DAC. The AD421 is a

complete, loop-powered, digital to 4-20mA converter, designed

to meet the needs of smart transmitter manufacturers in the

Industrial Control industry. It provides a high precision, fully

integrated, low cost solution in a compact 16-pin package. The

AD421 is ideal for extending the resolution of smart 4-20mA

transmitters at very low cost.

The AD421 includes a selectable regulator which can be used to

power all other devices in the transmitter. This regulator

provides either a +5 V, +3.3 V or +3 V regulated output

voltage. The part also contains +1.25 V and +2.5 V precision

references. The AD421 thus eliminates the need for a discrete

regulator and voltage reference. The only external components

required are a number of passive components and a pass

transistor to span large loop voltages. Full data on the AD421 is

available in the AD421 data sheet available from Analog

Devices and should be consulted in conjunction with this

Application Note when using the Evaluation Board.

REV. A

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

FEATURES

Loop Powered

5V, 3.3V and 3V Modes of Operation

Direct Hook-Up to Printer Port of PC

PC Software for Control of Loop Current

36-WAY

CENTRONICS

CONNECTOR

FUNCTIONAL BLOCK DIAGRAM

LEVEL

SHIFTERS/

BUFFERS

GND

V CC

Included on the evaluation board, along with the AD421, are a

DN2535/DN2540, an N-Channel depletion mode FET which is

used as part of the regulator loop to regulate the supply for the

board from the externally supplied loop voltage applied between

the loop(+) and loop (-) inputs, digital buffers to buffer and

level shift the input signals from the printer port edge connector

and a number of passive components required to achieve

optimum performance from the AD421.

Interfacing to the AD421 board is provided via a 36-Pin

Centronics Connector.

OPERATING THE AD421 EVALUATION BOARD

Power Supplies

The evaluation board operates from a single power supply

connected between the LOOP PLUS and LOOP MINUS

terminals on the board. This loop power supply must be floating

with respect to the computer ground and have a minimum limit

of V

the external pass transistor. The pass transistor used on this

board is a DN2535/DN2540, N-Channel Depletion mode

transistor available from Supertex inc.., this facilitates the use of

loop voltages up to 350V. This pass transistor in association

with the regulator loop of the AD421 regulates the supply

voltage for the AD421 itself and for the digital buffers on the

board. The regulated voltage is referenced to the COM pin on

the AD421. A link option on the board selects the operating

mode for the board to be either 5V, 3.3V or 3V.

The regulated voltage on the AD421 V

10 F tantalum and 0.1 F ceramic disc capacitors.

The loop current can be measured in either the LOOP PLUS or

LOOP MINUS lines.

One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.

Tel: 617/329-4700

AD421

COM

+2 V and a maximum limit of the breakdown voltage of

DN2535/

DN2540

DRIVE

LOOP

RTN

Loop Powered 4-20mA DAC

Evaluation Board for

LOOP

MINUS

LOOP

PLUS

EVAL-AD421EB

pin is decoupled with

Fax: 617/326-8703

Related parts for EVAL-AD421EB

EVAL-AD421EB Summary of contents

Page 1

... LOOP MINUS lines. FUNCTIONAL BLOCK DIAGRAM DN2535/ DN2540 DRIVE LEVEL AD421 SHIFTERS/ BUFFERS LOOP GND RTN COM One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A. Tel: 617/329-4700 Evaluation Board for EVAL-AD421EB pin is decoupled with CC LOOP PLUS LOOP MINUS Fax: 617/326-8703 ...

Page 2

... EVAL-AD421EB Link Options There is one link option on the evaluation board which should be set for the required operating setup before using the board. The function of this link option is described below. LK1 Function This option is used to control the selectable regulator on the AD421 that is used to power the AD421 itself and the digital buffers on the board ...

Page 3

... Laptop etc). LPT1 works for most machines and is the default selection. When using a Compaq laptop, select PRN. A different port can be selected at any time from the MAIN MENU. REV. A Figure 2. Parallel Port Selection. Figure 3. Main Window. –3– EVAL-AD421EB ...

Page 4

... EVAL-AD421EB The evaluation software does not allow another application running under Windows to access the printer port while it is running. Control of the printer port is returned when the AD421 application program is quit. MAIN MENU WINDOW Once the OK button of the port selection window has been pressed the user is presented with the Main Menu Window for the application ...

Page 5

... REV. A –5– EVAL-AD421EB ...

Page 6

... EVAL-AD421EB Intergrated Circuits Component Location AD421 U1 DN2535/DN2540 U2 74HC4050 U3 Capacitors Component Location 0.01 F Ceramic C1, C2 0.0033 F Ceramic C3 4.7 F 20% Tantalum (16 V) C4, C5 0.01 F Ceramic(X7R 20%) C6, C10 10 F 20% Tantalum ( 0.1 F Ceramic(X7R 20%) C8, C11 1000pF Ceramic C9 Resistors Component Location 1k 5% 0.25W Carbon Film Resistor ...

Page 7

... Further development work on the AD421 evaluation board is being planned to see if the above performance can be improved upon. –7– EVAL-AD421EB ...

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