EVAL-SDP-CB1Z View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-SDP-CB1Z' PDF : 28 Pages View PDF
TRUE 16-BIT ISOLATED APPLICATION EXAMPLE
In applications where high accuracy and isolation are required,
for example, power monitoring, motor control, and some
medical equipment, the circuit given in Figure 48, using the
AD7685 and the ADuM1402C digital isolator, provides a
compact and high performance solution.
±10V INPUT
5V REF
10µF
4kΩ
1kΩ
5V
100nF
5V
2V REF
1/4 AD8618
REF VDD VIOSDO
IN+
AD7685
SCK
CNV
IN– GND
SDI
±10V INPUT
5V REF
10µF
4kΩ
1kΩ
5V
100nF
5V
2V REF
1/4 AD8618
REF VDD VIOSDO
IN+
AD7685
SCK
CNV
IN– GND
SDI
AD7685
Multiple AD7685s are daisy-chained to reduce the number of
signals to isolate. Note that the SCKOUT, which is a readback of
the AD7685’s clock, has a very short skew with the DATA
signal. This skew is the channel-to-channel matching
propagation delay of the digital isolator (tPSKCD). This allows
running the serial interface at the maximum speed of the digital
isolator (45 Mbps for the ADuM1402C), which would have
been otherwise limited by the cascade of the propagation delays
of the digital isolator.
The complete analog chain runs on a 5 V single supply using
the ADR391 low dropout reference voltage and the rail-to-rail
CMOS AD8618 amplifier while offering true bipolar input range.
5V
100nF
VDD1, VE1
GND1
VIA
VIB
VOC
VOD
VDD2, VE2
GND2
VOA
VOB
VIC
VID
2.7V TO 5V
100nF
DATA
SCKOUT
SCKIN
CONVERT
ADuM1402C
±10V INPUT
5V REF
10µF
4kΩ
1kΩ
5V
100nF
5V
2V REF
1/4 AD8618
REF VDD VIOSDO
IN+
AD7685
SCK
CNV
IN– GND
SDI
±10V INPUT
5V REF
10µF
4kΩ
1kΩ
5V
100nF
5V
2V REF
1/4 AD8618
REF VDD VIOSDO
IN+
AD7685
SCK
CNV
IN– GND
SDI
1kΩ
1kΩ
5V
ADR391
1kΩ
5V IN OUT
GND
5V REF
2V REF
4kΩ
10µF 100nF
Figure 48. A True 16-Bit Isolated Simultaneous Sampling Acquisition System
Rev. C | Page 25 of 28
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