MCP4822 Microchip Technology, MCP4822 Datasheet - Page 29

• Manufacturer Part Number: MCP4822
• Description: 8/10/12-Bit Dual Voltage Output Digital-to-Analog Converter
• Manufacturer: Microchip Technology

6.7
In some applications, precision digital control of the
output range is desirable.
to use the MCP4802/4812/4822 family of devices to
achieve this in a bipolar or single-supply application.
EXAMPLE 6-4:
 2010 Microchip Technology Inc.
Dual Output DAC:
Thevenin
Equivalent
Selectable Gain and
Offset Bipolar Voltage Output
Using a Dual Output DAC
V
V
MCP4802
MCP4812
MCP4822
OUTB
OUTA
V
IN+
V
O
=
=
=
=
V
SPI
V
IN+
2.048 G
2.048 G
V
------------------------------------------------ -
Offset Adjust Gain Adjust
V
45
OUTB
IN+
BIPOLAR VOLTAGE SOURCE WITH SELECTABLE GAIN AND OFFSET
=
=




R
1
3
V
----------------------------------------------- -
Example 6-4
R
V
-------------------------------------------- -
3
+
OUTB
V
V
CC+
4
B
A
+
DAC
DAC
DD
DD
+
R
----- -
R


R
2
1
D
------
R
R
D
------
2
2
V
R


4
N
N
4
3
n
R
n
CC-
4
A
–
B
+
+
+
45
V
R
R
R
V
OUTA
+
Bipolar “Window” DAC using R
3
5
45
CC-
V
(DAC
(DAC
illustrates how
45
V
V
R


OUTA
OUTB
R
5
R
----- -
R
3
2
1
A
B


for Gain Adjust)
for Offset Adjust)
R
V
45
O
=
=
D
A ,
Offset Adjust Gain Adjust
------------------ -
R
V
R
4
IN+
R
D
4
R
+
G
N
B
3
R
1


R
5
1
This circuit is typically used for linearizing a sensor
whose slope and offset varies.
The equation to design a bipolar “window” DAC would
be utilized if R
5
=
=
=
=
=
+
V
MCP4802/4812/4822
CC
R
----- -
R
Gain selection (1x or 2x)
DAC bit resolution
Digital value of DAC (0-255) for MCP4802
Digital value of DAC (0-1023) for MCP4812
Digital value of DAC (0-4095) for MCP4822
2
1
–


V
4
–
CC
R
R
and R
V
4
5
+
OUTA
V
IN
0.1 µF
3
+
, R
5


R
----- -
R
4
2
1


and R
5
V
V
are populated.
CC
R
CC
2
+
–
DS22249A-page 29
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V
O