DAC8222 Analog Devices, DAC8222 Datasheet - Page 10

• Manufacturer Part Number: DAC8222
• Description: Dual 12-Bit Double-Buffered Multiplying CMOS D/A Converter
• Manufacturer: Analog Devices

Specifications of DAC8222

• Resolution (bits): 12bit
• Dac Update Rate: 1MSPS
• Dac Settling Time: 1µs
• Max Pos Supply (v): +15.75V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: Par

DAC8222
APPLICATIONS INFORMATION
UNIPOLAR OPERATION
Figure 24 shows a simple unipolar (2-quadrant multiplication)
circuit using the DAC8222 and OP270 dual op amp (use two
OP42s for higher speeds), and Table II the corresponding code
table. Resistors R1, R2, and R3, R4 are used only if full-scale
gain adjustments are required. Low temperature coefficient
(approximately 50 ppm/°C) resistors or trimmers should be
used. Maximum full-scale error without these resistors for the
top grade device and V
the low grade. C1 and C2 provide phase compensation to help
reduce overshoot and ringing when high speed op amps are used.
Full-scale adjustment is accomplished by loading the digital
inputs with all 1s and adjusting R1 (or R3) so that
Full-scale can also be adjusted by varying V
eliminating R1, R2, R3 and R4. Zero adjustment is performed
by setting the DAC’s digital inputs to all 0s and adjusting the op
amp’s offset adjust so that V
ity and minimize gain and linearity errors, it is recommended
that the op amp offset voltage be adjusted to less than 10% of
1 LSB (244 µV) over the operating temperature range of interest.
V
OUT
REF
= V
= ± 10 V is 0.024% and 0.097% for
OUT
REF
= 0 V. To maintain monotonic-
×


4096
4095


REF
voltage, thus
** REGISTERS AND CONTROL CIRCUITRY OMITTED FOR SIMPLICITY.
* RESISTORS R1 THROUGH R4 ARE ONLY NECESSARY TO TRIM FOR
ABSOLUTE ACCURACY BETTER THAN
COMPLETE DETAILS.
BIPOLAR OPERATION
The bipolar (offset binary) four-quadrant operation configura-
tion using the DAC8222 is shown in Figure 25 and the corre-
sponding code in Table III. The circuit makes use of the OP470
a quad op amp (use four OP42s for higher speeds).
Resistors R1, R2, R3, and R4 may be omitted and full-scale
output voltage may be adjusted by varying V
of R5 and R8. If resistors R1, R2, R3, and R4 are omitted,
Binary Number in
DAC Register
MSB
1111 1111 1111
1000 0000 0000
0000 0000 0001
0000 0000 0000
NOTE
1 LSB = (2
Table II. Unipolar Binary Code Table (Refer to Figure 24)
–12
) (V
REF
LSB
) =
4096
1
(V
REF
0.01%, SEE TEXT FOR
Analog Output, V
(DAC A or DAC B)
–V
–V
–V
0 V
)
REF
REF
REF






4095
4096
2048
4096
4096
1






= –1/2 V
REF
OUT
or the value
REF