Datasheet

AD7225
Rev. C | Page 13 of 24
UNIPOLAR OUTPUT OPERATION
This is the basic mode of operation for each channel of the
AD7225, with the output voltage having the same positive
polarity as V
REF
x. The AD7225 can be operated single supply
(V
SS
= AGND) or with positive/negative supplies (see the Op
Amp Section, which outlines the advantages of having negative
V
SS
). Connections for the unipolar output operation are shown
in Figure 16. The voltage at any of the reference inputs must
never be negative with respect to DGND. Failure to observe this
precaution may cause parasitic transistor action and possible
device destruction. The code table for unipolar output
operation is shown in Table 7.
Note,
( )
( )






==
−
256
1
21
8
REFREF
VVLSB
V
REF
A V
REF
B V
REF
C V
REF
D V
DD
V
SS
AGND DGND
V
OUT
A
DAC A
V
OUT
B
DAC B
V
OUT
C
DAC C
V
OUT
D
DAC D
DB7
(MSB)
DB0
(LSB)
A1
A2
WR
LDAC
AD7225
00986-016
Figure 16. Unipolar Output Circuit
Table 7. Unipolar Code Table
DAC Latch Contents
Analog Output
MSB LSB
1111 1111
( )
256
255
REF
V+
1000 0001
( )
256
129
REF
V+
1000 0000
( )
2
256
128
REF
REF
V
V +=+
0111 1111
( )
256
127
REF
V+
0000 0001
( )
256
1
REF
V+
0000 0000 0 V