AD7225LP Analog Devices Inc, AD7225LP Datasheet - Page 14
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AD7225LP
Manufacturer Part Number
AD7225LP
Description
IC DAC 8BIT QUAD W/AMP 28-PLCC
Manufacturer
Analog Devices Inc
Datasheet
1.AD7225CRSZ.pdf
(24 pages)
Specifications of AD7225LP
Rohs Status
RoHS non-compliant
Settling Time
4µs
Number Of Bits
8
Number Of Converters
4
Voltage Supply Source
Dual ±
Power Dissipation (max)
500mW
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
28-LCC (J-Lead)
Data Interface
-
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AD7225
BIPOLAR OUTPUT OPERATION
Each of the DACs of the AD7225 can be individually confi-
gured to provide bipolar output operation. This is possible
using one external amplifier and two resistors per channel.
Figure 17 shows a circuit used to implement offset binary
coding (bipolar operation) with DAC A (DAC Channel A)
of the AD7225. In this case,
With R1 = R2
where D
Latch A (0 ≤ D
Mismatch between R1 and R2 causes gain and offset errors and,
therefore, these resistors must match and track over tempera-
ture. The AD7225 can be operated in single supply or from
positive/negative supplies. Table 8 shows the digital code vs.
output voltage relationship for the circuit of Figure 17 with
R1 = R2.
V
V
OUT
OUT
A
is a fractional representation of the digital word in
=
=
+
(
2
1
D
A
≤ 255/256).
A
R2
R1
−
1
)
×
×
(
D
(
V
A
REF
V
REF
)
)
−
R2
R
1
×
(
V
REF
)
Rev. C | Page 14 of 24
Table 8. Bipolar (Offset Binary) Code Table
MSB
1111
1000
1000
0111
0000
0000
V
AD7225*
REF
DAC Latch Contents
V
SS
DAC A
V
Figure 17. Bipolar Output Circuit
AGND
LSB
1111
0001
0000
1111
0001
0000
REF
A
V
DGND
DD
V
R1, R2 = 10kΩ ± 0.1%.
*DIGITAL INPUTS OMITTED
OUT
FOR CLARITY.
Analog Output
0 V
+
+
−
−
−
A
V
V
V
V
V
R1
REF
REF
REF
REF
REF
( )
( )
( )
( )
( )
127
128
128
127
128
+15V
128
128
128
–15V
1
1
R2
=
1
−
V
V
OUT
REF