Analog Devices EVAL-AD7715-5EB Manuale utente

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

Tel: 617/329-4700 Fax: 617/326-8703

Evaluation Board for

16-Bit Sigma Delta ADC

EVAL-AD7715-5EB

FEATURES

Operates from a Single +5V Supply

On-Board Reference and Digital Buffers

Various Linking Options

Direct Hook-Up to Printer Port of PC

PC Software for Control and Data Analysis

OPERATING THE AD7715-5 EVALUATION BOARD

Power Supplies

The evaluation board has four power supply input pins: AV

AGND, DV

and DGND. The AD7715-5 is specified with an

of +5V. Therefore, the AV

voltage supplied to the

board must be +5V. This AV

voltage is also used to power the

AD780 reference. The AD7715-5 can be operated from a +5V

or +3V DV

voltage. When using the 9-way D-type connector

to interface to the evaluation board it is possible to apply a

voltage of either +3V or +5V to the DV

input terminal

on the board. However, when using the 36-way Centronics

connector to interface to the board, the voltage applied to the

input terminal must be +5V. This is because the

Centronics connector is intended for connection to the printer

port of a PC with signals driven from +5V supplies. To run the

board from a single +5V supply, simply connect the AV

and

inputs together.

Both AGND and DGND inputs are provided on the board.

AGND connects to the AD7715-5 AGND pin and also con-

nects to the GND pin of the AD780. DGND connects to the

DGND pin of the AD7715 and to the GND of the digital chips

on the board. The AGND and DGND planes are connected at

the AD7715. Therefore, it is recommended not to connect

AGND and DGND elsewhere in the system to avoid ground

loop problems. When using a single supply for both AV

and

, only one ground connection should be made to the

board. This connection should be made to the board's AGND

input terminal.

Both supplies are decoupled to their respective ground plane

with 10µF tantalum and 0.1µF ceramic disc capacitors.

AD7715

ADC

9-WAY D-TYPE CONNECTOR

36-WAY

CENTRONICS

CONNECTOR

AD780

REFERENCE

AIN(+)

AIN(-)

AVDD AGND DVDD DGND

REF IN

BUFFERS

MCLK IN

INTRODUCTION

This Application Note describes the evaluation board for the

AD7715-5, 16-Bit signal conditioning ADC. The AD7715 is a

complete analog front end for low-frequency applications

providing a fully-differential input channel. The device accepts

low-level signals directly from a transducer and outputs a serial

digital word. It employs a sigma delta technique to realize up to

16 bits of no missing codes performance. Full data on the

AD7715-5 is available in the AD7715 data sheet available from

Analog Devices and should be consulted in conjunction with

this Application Note when using the Evaluation Board.

Included on the evaluation board, along with the AD7715-5, are

an AD780, a +2.5 V ultra high precision bandgap reference, a

2.4576MHz crystal and digital buffers to buffer signals to and

from the edge connectors.

Interfacing to this board is provided either through a 36-Way

Centronics Connector or through a 9-way D-type connector.

External sockets are provided for the analog inputs, an external

reference input option and an external master clock option.

FUNCTIONAL BLOCK DIAGRAM

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.

EVAL-AD7715-5EB

REV. A–2–

Link Options

There are a number of link options on the evaluation board which should be set for the required operating setup before using the

board. The functions of these link options are described in detail below.

Link No. Function

LK1 This option selects the master clock option for the AD7715. The master clock source comes from the on-board

crystal or from an external clock source via SKT7. This is a double link and both links must be moved together for

correct operation.

With both links in position A, the external clock option is selected and an externally applied clock to SKT 7 is routed

the MCLK IN pin of the AD7715.

With both links in position B, the on-board crystal is selected and provides the master clock for the AD7715.

LK2 This link option is used to select the reference source for the AD7715's REF IN(-) input.

With this link in position A, the REF IN(-) pin of the AD7715 is connected directly to AGND.

With this link in position B, the REF IN(-) pin of the AD7715 is connected to SKT5. An external voltage connected

to SKT5 can now be used for REF IN(-).

LK3 This link option is used to select the reference source for the AD7715's REF IN(+) input.

With this link in position A, the REF IN (+) pin of the AD7715 is connected directly to the output of the on-board

reference, the AD780.

With this link in position B, the REF IN(+) pin of the AD7715 is connected to SKT6. An external voltage connected

to SKT 6 can now be used for REF IN(+).

LK4 This link option is set depending on the type of reference being used on the evaluation board. Although the board is

equipped with an AD780, a REF-192 +2.5V reference can replace it in the same socket. When a REF-192 reference

is used on the board, the link should be in either position A or position B. In position A, the REF-192's shutdown pin

is connected to DV

, placing the REF-192 in normal mode of operation. In position B, the REF-192's shutdown pin

is connected to DGND, placing the REF-192 in power down mode.

When the AD780 reference is used, the link should be in position C as the AD780 does not have a shutdown pin.

LK5 This link is in series with the AIN (+) analog input.

With this link in place, the analog input on the SKT3 input is connected directly to the AIN(+) input on the part.

This link may be removed so that the input signal at SKT3 can be connected to the component grid for signal

conditioning before being applied to the AIN(+) input of the AD7715.

LK6 This link is in series with the AIN (-) analog input.

With this link in place, the analog input on the SKT4 input is connected directly to the AIN(-) input on the part.

This link may be removed so that the input signal at SKT4 can be connected to the component grid for signal

conditioning before being applied to the AIN(-) input of the AD7715.

EVAL-AD7715-5EB

REV. A –3–

Setup Conditions

Table I shows the position in which all the links are set when the

evaluation board is sent out.

Table I. Initial Link Positions

Link No. Position Function.

LK1 B Both links in position B to select the

on-board crystal oscillator as the master

clock for the board.

LK2 A REF IN(-) connected directly to

AGND.

LK3 A REF IN(+) connected to the output of

the on-board AD780 reference.

LK4 C Selects AD780 as the voltage reference.

LK5 IN Connects input signal from SKT3

directly to the AIN(+) pin of the

AD7715.

LK6 IN Connects input signal from SKT4

directly to the AIN(-) pin of the

AD7715.

Figure 2. SKT1 Pin Configuration

2431 5

6789

Table II. SKT1 Pin Designations

1 SCLK Serial Clock. The signal on this pin is buffered

before being applied to the SCLK pin of the

AD7715.

2DRDY Logic Output. This is a buffered version of the

signal on the AD7715's DRDY pin.

3CS Chip Select. The signal on this pin is buffered

before being applied to the CS pin of the

AD7715.

4RESET Reset Input. The signal on this pin is buffered

before being applied to the RESET pin of the

AD7715.

5 DIN Serial Data Input. Data applied to this pin is

buffered before being applied to the AD7715's

DIN pin.

6 DGND Ground reference point for digital circuitry.

Connects to the DGND plane on the evaluation

board.

7 DOUT Serial Data Output. This is a buffered version of

the signal on the AD7715's DOUT pin.

8DV

Digital Supply Voltage. The DV

voltage for

the evaluation board can be supplied via this pin

provided no voltage is applied to the main DV

terminal.

9 NC No Connect. This pin is not connected on the

evaluation board.

NOTE

An explanation of the AD7715 functions mentioned here is given in Table III as

part of the SKT2 pin designations description.

EVALUATION BOARD INTERFACING

Interfacing to the evaluation board is either via a 9-way D-Type

connector, SKT1, or a 36-way Centronics connector, SKT2.

The pinout for the SKT1 connector is given in Figure 1 and its

corresponding pin designations are given in Table II. The

pinout for this SKT2 connector is shown in Figure 2 and its pin

designations are given in Table III. The evaluation board should

be powered up before a cable is connected to either of the

connectors.

SKT2 is used to connect the evaluation board to the printer

port (parallel port) of a PC. Connection between the two is

direct via a standard parallel printer port cable. SKT1 is used to

connect the evaluation board to any other system.

EVAL-AD7715-5EB

REV. A–4–

118

1936

Figure 3. SKT2 Pin Configuration

Table III. SKT2 Pin Designations

1 NC No Connect. This pin is not connected on the evaluation board.

2 DIN Serial Data Input. Data applied to this pin is buffered before being applied to the AD7715's DIN pin. The

serial data applied to the DIN pin is written to the input shift register on the part. Data from this input shift

bits of the Communications Register.

3RESET Reset Input. The signal on this pin is buffered before being applied to the RESET pin of the AD7715.

RESET is an active low input which resets the control logic, interface logic, calibration coefficients, digital

filter and analog modulator of the part to power-on status.

4CS Chip Select. The signal on this pin is buffered before being applied to the CS pin of the AD7715. CS is an

active low logic input used to select the AD7715. With this input hard-wired low, the AD7715 operates in its

three-wire interface mode with SCLK, DIN and DOUT used to interface to the device. CS can be used to

select the device in systems with more than one device on the serial bus or as a frame synchronisation signal

in communicating with the AD7715.

5 SCLK Serial Clock. The signal on this pin is buffered before being applied to the SCLK pin of the AD7715. An

external serial clock is applied to this input to access serial data from the AD7715. This serial clock can be a

continuous clock with all data transmitted in a continuous train of pulses. Alternatively, it can be a non-con-

tinuous clock with the information being transmitted to the AD7715 in smaller batches of data.

6-8 NC No Connect. These pins are not connected on the evaluation board.

9DV

Digital Supply Voltage. This provides the supply voltage for IC4, the buffer chip which buffers the output

signals from the AD7715 before they are applied to SKT2.

10 DRDY Logic output. This is a buffered version of the signal on the AD7715's DRDY pin. A logic low on the DRDY

output indicates that a new output word is available from the AD7715 data register. The DRDY pin will

return high upon completion of a read operation of a full output word. If no data read has taken place, after

an output update, the DRDY line will return high for 500* t

CLK IN

cycles prior to the next output update.

This gives an indication of when a read operation should not be attempted to avoid reading from the data

calibration sequence.

11-12 NC No Connect. These pins are not connected on the evaluation board.

13 DOUT Serial Data Output. This is a buffered version of the signal on the AD7715's DOUT pin. Serial data from

the output shift register on the part is clocked out on this pin. This output shift register can contain informa-

tion from the communications register, setup register or data register depending on the register selection bits

of the Communications Register.

14-18 NC No Connect. These pins are not connected on the evaluation board.

19-30 DGND Ground reference point for digital circuitry. Connects to the DGND plane on the evaluation board.

31-36 NC No Connect. These pins are not connected on the evaluation board.

EVAL-AD7715-5EB

REV. A –5–

SOCKETS

There are seven sockets on the AD7715-5 evaluation board.

The function of these sockets is outlined in Table IV.

Table IV. Socket Functions

Socket Function

SKT1 9-Way D-Type Connector which can be used for

digital interfacing to the evaluation board.

SKT2 36-Way Centronics Connector which can be used

for digital interfacing to the evaluation board. This

connector should be used when connecting the

board to the parallel printer port of the PC to use

the evaluation software.

SKT3 Sub-Minature BNC Connector. The analog input

signal for the AIN(+) input of the AD7715 is

applied to this socket.

SKT4 Sub-Minature BNC Connector. The analog input

signal for the AIN(-) input of the AD7715 is

applied to this socket.

SKT5 Sub-Minature BNC Connector. The reference

voltage for the REF IN(-) input of the AD7715 is

applied to this socket when the board is configured

for an externally-applied reference voltage.

SKT6 Sub-Minature BNC Connector. The reference

voltage for the REF IN(+) input of the AD7715 is

applied to this socket when the board is configured

for an externally-applied reference voltage.

SKT7 Sub-Minature BNC Connector. The master clock

signal for the MCLK IN input of the AD7715 is

applied to this socket when the board is configured

for an externally-applied master clock.

RUNNING THE AD7715 INTERFACE SOFTWARE

Included in the evaluation board package is a PC-compatible

disk which contains software for controlling and evaluating the

performance of the AD7715 using the printer port of a PC.

There are a total of thirteen files on the distribution disk.

To use the software, the user must have an IBM-compatible PC

and Windows 3.1 must be installed. Start Windows and, using

either the RUN command or the file manager, start the program

called SETUP.EXE on the distribution disk. This automatically

installs the application and sets up a window called ANALOG

DEVICES. The application ICON is found here. To start the

application, double click on the ICON.

When the program stsrts, the user is asked to select a printer

port. The correct selection depends on what type of computer is

being used (Desktop, Laptop etc). LPT1 works for most

machines. When using a Compaq laptop, select PRN. A

different port can be selected at any time from the MAIN

MENU.

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

application is quit.

EVAL-AD7715-5EB

REV. A–6–

SCLK

DGND

AGND

AIN(+)

AIN (-)

AV DD

DVDD

REF IN(+) 9

LK3

SKT6

AD780/

IC2

REF IN(-) 10 BA

SKT5

AD7715

IC1

MCLK OUT 3

LK1

MCLK IN 2AB

SKT7

XTAL1

DRDY

DIN 14

13 4

DOUT

IC3

74HC4050

10µF C6

0.1µF

10µF C4

0.1µF

10µF C2

0.1µF

AVDD

C12

0.1µF

SW 1 RESET

R6 10kΩ

SKT1

SCLK

DOUT

DIN

DRDY

DGND

RESET

DV DD

11 12

14 15

C10

0.1µF

C14 C13

LK4

REF-192

DIN 3

RESET

SCLK

36 PIN CENTRONICS CONNECTOR

ACK

DRDY

10 SLCT

DOUT

GND

19 - 30

DGND DVDD

IC4

74LS08

1213

IC5

74LS244

811

914

16 1

C11

0.1µF

R5 10kΩ

R4 3.3kΩ

HP 5082- 2810

SKT 2

0.1µF

LK 6

LK 5

SKT3

SKT4

DGND

AGND

HP 5082- 2810

DVDD

LK2

Figure 3. AD7715-5 Evaluation Board Circuit Diagram

EVAL-AD7715-5EB

REV. A –7–

COMPONENT LISTING AND MANUFACTURERS

Intergrated Circuits

Component Location Vendor

AD7715 IC1 Analog Devices

AD780 IC2 Analog Devices

74HC4050 IC3 Philips

74LS08 IC4 Texas Instruments

74LS244 IC5 Texas Instruments

HP 5082-2810 D1 & D2 Hewlett Packard

Capacitors

Component Location Vendor

10µF ±20% Tantalum (16 V) C1, C3, C5 AVX- Kyocera

Mftrs No TAG106MO16

0.1µF Ceramic(X7R ±20%) C2, C4, C6, C9, Philips

C10, C11 Mftrs No. CW20C 104M

33pF ±2% Ceramic C13, C14 Philips

Mftrs No. 683 34339

Open Circuit C7, C8,

Resistors

Component Location Vendor

10kΩ±5% 0.25W

Carbon Film Resistor R5, R6 Bourns

3.3kΩ±5% 0.25W

Carbon Film Resistor R4 Bourns

1MΩ±5% 0.25W

Carbon Film Resistor R3 Bourns

Short Circuits R1, R2

Link Options

Component Location Vendor

Pin Headers Lk1 (4x2 way) Harwin

Lk2, Lk3 Mftrs No. M20-9993606

( 2x2 way)

Lk4

(3x2 way)

Lk5, Lk16

(1x2 way)

Shorting Plugs Pin Headers Harwin

(7 required) Mftrs No. M7571-05

EVAL-AD7715-5EB

REV. A–8–

Switch

Component Location Vendor

Push Button Switch SW1 Omron

Mftrs No. B3F1000

Sockets

Component Location Vendor

Miniature BNC Connectors SKT3 - SKT 7 M/A - Com Greenpar

Mftrs No. C65N07G999X99

9-Way D-Type Connector SKT1 McMurdo

Mftrs No. SDE9PNTD

36 Way Centronics Connector SKT 2 Fujitsu

Mftrs No. FCN785J036G0

16-Pin IC Socket IC1 Harwin

8 Pin IC Socket IC2 Mftrs No. D28xx-01

16-Pin IC Socket IC3 xx = No. of Pins

14- Pin IC Socket IC4

20-Pin IC Socket IC5

Wire Wrap Pins DGND, AGND, AVDD, Bicc Vero

DVDD Mftrs No. 663472C

Crystal Oscillator

Component Identification Location Vendor

2.4576MHz Oscillator Xtal 1 IQD

Mftrs No. A166C

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