herunterladen
AN-893
APPLICATION NOTE
One Technology Way • P. O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel : 781.329.4700 • Fax: 781.461.3113 • www.analog.com
Configuring the AD7656/AD7657/AD7658 for
Serial and Daisy-Chain Interface Modes of Operation
by Claire Croke
Rev. 0 | Page 1 of 8
INTRODUCTION
The AD7656/AD7657/AD7658 can be configured to operate in
three interface modes: parallel interface mode, serial interface
mode, or daisy-chain interface mode. The parallel mode of
operation is covered extensively in the
AD7656/AD7657/AD7658
data sheet. In addition to the information provided in the data
sheet, this application note further describes how to configure
the
AD7656 for the serial and daisy-chain interface modes.
FUNCTIONAL BLOCK DIAGRAM
V
SS
DGND
V
DD
REF
CONVST
A
CONVST B CONVST C
OUTPUT
DRIVERS
OUTPUT
DRIVERS
OUTPUT
DRIVERS
OUTPUT
DRIVERS
CONTROL
LOGIC
BUF
BUF
BUF
AGND
T/H
T/H
T/H
T/H
T/H
T/H
CLK
OSC
AV
CC
DV
CC
V
1
V
2
V
3
V
4
V
5
V
6
SER/PAR
CS
V
DRIVE
STBY
DOUT A
DOUT B
DOUT C
SCLK
RD
WR
DATA/
CONTROL
LINES
06509-001
AD7656/AD7657/AD7658
16-/14-/12-BIT SAR
16-/14-/12-BIT SAR
16-/14-/12-BIT SAR
16-/14-/12-BIT SAR
16-/14-/12-BIT SAR
16-/14-/12-BIT SAR
Figure 1.
CONFIGURING THE AD7656, AD7657, AND
AD7658 FOR SERIAL INTERFACE MODE
The SER/
PAR
/SEL pin on the AD7656 is used to select between
the parallel interface mode and the serial interface mode. To select
the serial interface mode, this pin must be tied to logic high. When
in serial interface mode, the
AD7656 should be configured for
the hardware select mode of operation and
H
/S SEL should be tied
to a logic low. In serial interface mode, the
AD7656 cannot be
configured for the software mode of operation.
When operating in serial interface mode, the
AD7656 must be
configured to select the number of serial DOUT lines required
by the application. SEL A, SEL B, and SEL C are used to enable
data output lines DOUT A, DOUT B, and DOUT C,
respectively. If only one DOUT line is required for the serial
interface, DOUT A should be used. To enable DOUT A, the SEL A
pin should be tied to logic high, and the SEL B and SEL C pins
should be tied to logic low. To configure the serial interface to
have two data output lines, DOUT A and DOUT B should be
used. To enable DOUT A and DOUT B, the SEL A and SEL B
pins should be tied to logic high, and SEL C should be tied to a
logic low. To configure the serial interface to operate with all three
data output lines, DOUT A, DOUT B, and DOUT C should be
enabled. To enable all three DOUT lines, the SEL A, SEL B, and
SEL C lines should be to tied to logic high (see
Figure 2, Figure 3,
and
Figure 4).
If only one or two DOUT lines are used for the serial interface, the
unused DOUT lines should be left unconnected. These unused
DOUT lines should have their respective SEL pin tied to logic low.
06509-002
SEL A
SER/PAR
V
DRIVE
DOUT A
SEL B
DOUT B NC
SEL C DOUT C NC
NC = NO CONNECT
AD7656
V
DRIVE
HS
Figure 2. AD7656 with One DOUT Line
06509-003
SEL A
SER/PAR
DOUT A
SEL B DOUT B
SEL C DOUT C NC
AD7656
V
DRIVE
NC = NO CONNECT
V
DRIVE
HS
Figure 3.
AD7656 with Two DOUT Lines
06509-004
SEL A
SER/PAR
DOUT A
HS
SEL B DOUT B
SEL C DOUT C
AD7656
V
DRIVE
NC = NO CONNECT
V
DRIVE
Figure 4.
AD7656 with Three DOUT Lines
