Datasheet
AD7280A
Rev. 0 | Page 18 of 48
VIN6
V
DD
V
SS
MASTER
PDhi
CShi
SCLKhi
SDOhi
CNVSThi
SDIhi
ALERThi
V
DD
PDhi
CShi
SCLKhi
SDOhi
CNVSThi
SDIhi
ALERThi
PD
CS
SCLK
SDI
CNVST
SDOlo
ALERTlo
V
REG
1µF
1µF
0.1µF
0.1µF
VIN5
VIN4
VIN3
VIN2
VIN1
VIN0
V
SS
DV
CC
AV
CC
ALERT
CNVST
PD
SDO
SCLK
SDI
CS
V
DRIVE
V
REG
DV
CC
AV
CC
ALERT
SDO
MASTER
V
REF
C
REF
V
DRIVE
C
REF
V
REF
SDOlo
ALERTlo
AD7280A
AD7280A
10kΩ
10kΩ
10kΩ
1kΩ
100nF
100nF
10kΩ
10kΩ
100nF
100nF
10kΩ
10kΩ
FERRITE
100nF
10kΩ
100nF
100nF
VIN6
VIN5
VIN4
VIN3
VIN2
VIN1
VIN0
10kΩ
10kΩ
100nF
10kΩ
10kΩ
1kΩ
1kΩ
10kΩ
100nF
100nF
10kΩ
10kΩ
100nF
10kΩ
100nF
100nF
100nF
10µF
OPTIONAL INTERFACE PINS
4-WIRE SPI INTERFACE
1µF
1µF
0.1µF
0.1µF
22pF
22pF
22pF
22pF
22pF
22pF
22pF
22pF
22pF
22pF
22pF
22pF
22pF
22pF
100nF
100nF10µF
V
DD
0
100nF
100nF10µF
V
DD
(n – 1)
V
DD
n
V
DD
1
V
DD
0
V
SS
0
V
DD
0
V
SS
V
DD
PDhi
CShi
SCLKhi
SDOhi
CNVSThi
SDIhi
ALERThi
PD
CS
SCLK
SDI
CNVST
SDOlo
ALERTlo
V
REG
DV
CC
AV
CC
ALERT
SDO
MASTER
V
REF
C
REF
V
DRIVE
VIN6
VIN5
VIN4
VIN3
VIN2
VIN1
VIN0
10kΩ
10kΩ
100nF
10kΩ
10kΩ
1kΩ
1kΩ
10kΩ
100nF
100nF
10kΩ
10kΩ
100nF
10kΩ
100nF
100nF
1µF
1µF
0.1µF
0.1µF
V
DD
(n – 1)
V
DD
n
1k
Ω
AD7280A
NOTES
ALL AD7280A DEVICES ON THE DAISY CHAIN
SHOULD BE LOCATED ON THE SAME PCB.
PLACE 22pF DAISY-CHAIN CAPACITORS
AS CLOSE AS POSSIBLE TO THEIR
TERMINATING PINS, THAT IS, CLOSE TO
THE PIN THAT HAS THE ARROW POINTING
TO IT ON THE DIAGRAM.
ROUTE V
DD
AND V
SS
TRACES TO ENSURE
A LOW IMPEDANCE CONNECTION BETWEEN THEM.
ROUTE DAISY-CHAIN TRACKS ON AN INNER
PCB LAYER.
ADD A V
SS
PLANE FROM THE UPPER SLAVE
DEVICE EXTENDED DOWN OVER AND UNDER
THE DAISY CHAIN TO ACT AS A SHIELD FOR
THE DAISY CHAIN.
PLACE AD7280A PARTS AS CLOSE TOGETHER
AS POSSIBLE ON THE BOARD TO MINIMIZE
THE LENGTH OF THE DAISY-CHAIN TRACKS.
FERRITES ON THE V
DD
LINES CAN BE REPLACED
WITH 20Ω RESISTORS EXCEPT IN THE CASE OF THE
V
SS
0 CONNECTION. IN THIS CASE, THE 20Ω RESISTOR
SHOULD BE REPLACED WITH A 0Ω RESISTOR.
1
2
3
4
5
6
7
2
3
4
5
6
7
DSP/MICRO-
PROCESSOR
09435-011
Figure 29. AD7280A Daisy-Chain Configuration