ANALOG DEVICES EVAL-AD7891-2CB Service Manual

查询EVAL-AD7891-2CB供应商

Evaluation Board for Single Supply,

a

FEATURES
Full-Featured Evaluation Board for the AD7891-2
EVAL-CONTROL BOARD Compatible
Stand Alone Capability
On-Board Analog Buffering and Reference
Various Linking Options
PC Software for Control and Data Analysis when used

with EVAL-CONTROL BOARD

INTRODUCTION

This Application Note describes the evaluation board for the
AD7891-2 12-Bit A/D converter. The AD7891-2 is an eight
channel data acquisition system that operates from a single +5 V
supply and accepts input signals in the ranges 0 to +5 V , 0 to
+2.5 V or ±2.5 V. It incorporates an input multiplexer, an on
chip track/hold amplifier, an internal +2.5 V reference and on­chip versatile interface structures that allow both serial and
parallel connection to a microprocessor. This flexible serial
interface allows the AD7891-2 to connect directly to Digital
Signal Processors (ADSP-2101, DSP56001, etc.) and Micro­controllers (8XC51, 68HC11, etc.). Full data on the AD7891­2 is available in the AD7891 data sheet available from Analog
Devices and should be consulted in conjunction with this
Application Note when using the Evaluation Board.

On-board components include an AD780 which is a pin
programmable +2.5 V or +3V ultra high precision bandgap
reference, a buffer amplifier to buffer the reference when using
inputs in the ± 2.5 V range and two AD713 quad op-amps to
buffer the analog inputs.

FUNCTIONAL BLOCK DIAGRAM

12-Bit 500 kSPS ADC

EVAL-AD7891-2CB

Interfacing to this board is through a 9-way D-type connector
and a 96-way connector. This 96-way connector is compatible
with the EVAL-CONTROL BOARD which is also available
from Analog Devices. External sockets are provided for the
conversion start input, analog inputs and an external reference
input option.

OPERATING THE AD7891-2 EVALUATION BOARD
Power Supplies

This evaluation board has four analog power supply inputs:

, DGND, +12 V and -12 V. The VDD supply is nominally

V

DD

+5 V and is used to power the AD7891-2 and the on-board
digital integrated circuits. The +12 V and -12 V supplies are
used to power the AD713 quad op-amps and the AD780 voltage
reference and the reference buffer. The DGND connection is to
the digital ground plane. This DGND ground plane connects to
the AGND ground plane at the AD7891-2. Therefore, it is
recommended not to connect AGND and DGND elsewhere in
the system. The various analog and digital supplies are provided
through the power-supply terminals on the board. When using
the AD7891-2 evaluation board with the EVAL-CONTROL
BOARD, all supplies are provided by the EVAL-CONTROL
BOARD.

All supplies are decoupled to ground with 10µF tantalum and

0.1µF ceramic disc capacitors. The +12 V and -12 V supplies
for the amplifiers are decoupled to the AGND plane while the

supply for the AD7891 is decoupled to the AGND plane

AV

DD

through a 10 µF capacitor and to the DGND plane through a

0.1 µF capacitor.

AIN 8

OP467

Prototyping Area

Range

Selection

Jumpers

OP467

Reference

Input

(+2.5 V)

AIN 1

Analog

Inputs

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.

Conversion

Start Input

AD7891-2

ADC

AD7891-1

Evaluation

Board

AD780

Reference

+12 V

-12 V

V

DGND

DD

One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: [phone] Fax: [phone]

9-Way

D-Type

Connector

96-Way Connecter

12

EVAL-AD7891-2CB

Link Options

There are thirty one link options on the evaluation board which must be set for the required operating setup before use. The func­tions of these options are outlined below.

Link No. Function
LK1 - LK8 LK1 to LK8 select the voltages applied to the inputs of the quad op-amp buffers. LK1 selects the voltage for

channel 1, LK2 selects the voltage for channel 2 etc.
In position A, the input is connected to the SMB connector.
In position B, the input is connected to AGND. If no voltage is present at the SMB connector then the link

should be in position B.

LK9 - LK16 LK9 to LK16 are used to select the voltages applied to the V

that is applied to V

, LK10 selects the voltage applied to V

IN1A

In position A the buffered input voltage from AINx is connected to V
In position B, V

is connected to AGND.

INXA

LK17 - LK24 LK17 to LK24 are used to select the voltage applied to the V

voltage that is applied to V

, LK18 selects the voltage that is applied to V

IN1B

In position A, the buffered reference voltage is applied to V
In position B, the buffered input voltage from AINx is connected to V
In position C, V

is connected to AGND.

INXB

LK25 This link option selects the reference source for the AD7891 REF OUT/REF IN pin.

With this link in position A, the reference connects to the SMB socket, SKT9.
In position B, the AD780 +2.5V reference is selected as the reference for the AD7891-2.
With this link out, the REF OUT/REF IN pin remains open-circuited, thus the reference source is the AD7891-2's

internal reference.

LK26 This link selects the V

In position A, the V
In position B, the V

source.

DD

supply is taken from the external VDD connector.

DD

supply is taken from the 96 way connector.

DD

LK27 This link selects the +12V source.

In position A, the +12V supply is taken from the external +12 V connector.
In position B, the +12V supply is taken from the 96 way connector.

LK28 This link selects the -12 V source.

In position A, the -12 V supply is taken from the external -12 V connector.
In position B, the -12 V supply is taken from the 96 way connector.

LK29 This link option selects the voltage applied to the STANDBY pin of the AD7891-2. The voltage applied to the

STANDBY pin can also be controlled from pin 9 of the 9-way D-type socket. If pin 9 of the 9-way D-type socket
is used to control the voltage applied to the STANDBY pin then LK29 should be left unconnected.

In position A, the STANDBY pin is connected to V

DD.

In position B, the STANDBY pin is connected to DGND.

LK30 This link option selects the source for the

In position A, the

CONVST pin is connected to the FL0 pin on the 96-way connector. When using the evaluation

CONVST input of the AD7891-2.

board with the EVAL-CONTROL BOARD, there are two program options, one where the
generated from the EVAL-CONTROL BOARD; the second where the
When the internal

CONVST program is used, this link must be in position A.

In position B, the signal applied to the SMB connector, SKT10 provides the

LK31 This link option selects the voltage applied to the MODE pin of the AD7891-2 and hence selects the interface

mode used for the part.
In position A, the MODE pin is connected to DGND, which selects the serial interface mode.
In position B, the MODE pin is connected to V

, which selects the parallel interface mode.

DD

inputs of the AD7891-2. LK9 selects the voltage

INXA

etc.

IN2A

.

INXA

inputs of the AD7891-2. LK17 selects the

INXB

INXB

.

INXB

etc.

IN2B

.

CONVST signal is

CONVST signal is externally supplied.

CONVST signal for the AD7891-2.

–2–

REV. A

EVAL-AD7891-2CB

SET-UP CONDITIONS

Care should be taken before applying power and signals to the
evaluation board to ensure that all link positions are as per the
required operating mode. Table I shows the position in which
all the links are set when the evaluation board is sent out.

Table I. Initial Link and Switch Positions

Link No. Position Function.

LK1 A Input to buffer 1 comes from V

IN1

SMB

connector.

LK2 - LK8 B Inputs to buffers 2 to 8 connected to

AGND.

LK9 - LK16 A V

inputs are connected to relevant

INXA

AINx buffers
LK17 - LK24 C V
LK25 B Connects the AD780's V

inputs are connected to AGND

INXB

pin to the

OUT

AD7891-2's REF OUT/REF IN pin

and thus selects the AD780 as the

reference source for the AD7891-2
LK26 B V

is supplied from the 96-way

DD

connector.
LK27 B +12 V is supplied from the 96-way

connector.
LK28 B -12 V is supplied from the 96-way

connector.
LK29 A

STANDBY pin is connected to V

AD7891-2 does not go into

STANDBY

DD

and

mode.
LK30 B Connects the AD7891-2's

CONVST

pin to the FL0 pin of the edge

connector.
LK31 B MODE pin is connected to VDD and

part is configured for its parallel

operating mode.

EVALUATION BOARD INTERFACING

Interfacing to the evaluation board is either via a 96-way
connector, J1 or a 9-way D-Type connector, J2. J1 is used to
connect the evaluation board to the EVAL-CONTROL
BOARD. It can also be used for parallel interface connections to
the evaluation board when operating the AD7891 in its parallel
interface mode without the EVAL-CONTROL BOARD. J2 is
used for serial interface connections when operating the
AD7891-2 in its serial interface mode. The pinout for the J1
connector is shown in Figure 1 and its pin designations are
given in Table II. The pinout for the J2 connector is given in
Figure 2 and its corresponding pin designations are given in
Table III.

1

A
B
C

1

32

32

Figure 1. Pin Configuration for the 96-Way
Connector, J1

96-Way Connector Pin Description

D0-D11 Data Bit 0 to Data Bit 11. These are three-

state TTL-compatible outputs from the
AD7891-2. Parallel data from the part is
obtained at these pins.

DGND Digital Ground. These lines are connected to

the digital ground plane on the evaluation
board. It allows the user to provide the digital
supply via the connector along with the other
digital signals.

RD Read. This is an active low logic input which

is used in conjunction with

CS low to enable

the data outputs.

CS Chip Select. This is an active low logic input

which is used in conjunction with
enable the data outputs and with

RD low to

WR to allow

input data to be written to the part.

WR Write Input. This is an active low logic input

used in conjunction with

CS to latch the
multiplexer address and software control
information.

FL0 Flag zero. This is a logic input and is con-

nected to the

CONVST logic input on the
device via LK17. A low to high transition on
this input puts the track/hold amplifier into its
hold mode and starts a conversion.

IRQ2 Interrupt Request 2. This is a logic output

and is directly connected to the

EOC logic
output on the device. This active low logic
output indicates the converter status. The end
of conversion is signified by a low-going pulse
on this line.

AGND Analog Ground. These lines are connected to

the analog ground plane on the evaluation
board.

AV

DD

Analog +5V Supply. These lines are con­nected to the V

supply line on the board.

DD

+12 V +12 V supply used to power op-amps and

voltage reference.

-12 V -12 V supply used to power op-amps.

REV. A

–3–

EVAL-AD7891-2CB

Table II. 96-Way Connector Pin Functions.

ROW PIN NO. MNEMONIC

B2D0
B3D1
A 4 DGND
B 4 DGND
C 4 DGND
B5D2
B6D3
B7D4
A9
B9D5
B10D6
C10
B11D7
A 12 DGND
B 12 DGND
C 12 DGND
B13D8
B14D9
B 15 D10
A 16 DGND
B 16 DGND
C 16 DGND
A 17 FL0
B 17 D11
C17
A 20 DGND
B 20 DGND
C 20 DGND
A 22 AGND
A 23 AGND
A 24 AGND
A 25 AGND
A 26 AGND
A 29 AGND
B 29 AGND
C 29 AGND
A31AV
B31AV
C31AV
A32AV
B32AV
C32AV

Note : The remainder of the pins on the 96-way connector are no connects.

RD

CS

IRQ2

SS

SS

SS

DD

DD

DD

1234

678

5

9

Figure 2. Pin Configuration for D-Type Connector, J2

Table III. J2 Pin Functions

PIN NO. MNEMONIC

1 SCLK
2
3
4

EOC

RFS

TFS

5 DATA IN
6 DGND
7 DATA OUT
8V

DD

9 STANDBY

9-Way D-Type Connector Pin Description

SCLK Serial Clock Input. When the device is in its serial

mode, an external serial clock is applied through this
input to obtain serial data from the part.

EOC End-of-Conversion. This output indicates the status of

conversion. A low going pulse on this line signifies the
end of a conversion.

RFS Receive Frame Synchronisation. When the device is in

its serial mode, an external

RFS signal is applied to this

input to obtain serial data from the part.

TFS Transmit Frame Synchronisation. When the part is in

serial mode, an external

TFS signal is applied to this

input when serial data is being written to the part

DATA IN Serial Data Input. Serial data to the part is

applied this input. The serial data should be valid on
the falling edge of SCLK for six edges after

TFS goes

low.

DGND Digital Ground. This line is connected to the digital

ground plane on the evaluation board. It allows the
user to provide the digital supply via the connector
along with the other digital signals.

DATA OUT Serial Data Output. Serial data from the part

is obtained at this output. The serial data is clocked
out by the rising edge of SCLK and is valid on the
falling edge of SCLK for sixteen edges after

RFS goes

low.

DD

+5 V Supply. This line is connected to the VDD supply

V

line on the evaluation board. It allows the user to
provide the digital supply via the connector along with
the other digital signals.

STANDBY Standby Input. When this input is at a logic

zero, the AD7891-2 is put into standby mode. Normal
operation of the part takes place when

STANDBY is

high.

–4–

REV. A