AD7225KP-REEL Analog Devices Inc, AD7225KP-REEL Datasheet - Page 14

• Manufacturer Part Number: AD7225KP-REEL
• Description: IC DAC 8BIT QUAD W/AMP 28-PLCC
• Manufacturer: Analog Devices Inc

Specifications of AD7225KP-REEL

• 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: -

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