MCP4821T-E/P MICROCHIP [Microchip Technology], MCP4821T-E/P Datasheet - Page 23

• Manufacturer Part Number: MCP4821T-E/P
• Manufacturer: MICROCHIP [Microchip Technology]

6.7
In some applications, precision digital control of the
output range is desirable. Example 6-4 illustrates how
to use the MCP482X family to achieve this in a bipolar
or single-supply application.
EXAMPLE 6-4:
© 2005 Microchip Technology Inc.
Thevenin
Equivalent
Selectable Gain and Offset Bipolar
Voltage Output Using A Dual DAC
SPI™
V
OUTB
V
IN+
V
O
3
=
=
=
MCP482X
MCP482X
V
V
V
Offset Adjust Gain Adjust
V
----------------------------------------------- -
V
V
IN+
DD
DD
2.048V G
45
OUTB
IN+
Bipolar Voltage Source with Selectable Gain and Offset.
=
=
⎛
⎝
R
1
R
V
---------------------------------------------- -
V
------------------------------------------- -
DAC
DAC
3
+
4
OUTB
CC+
+
R
----- -
R
+
R
2
1
B
V
V
V
⎞
⎠
R
R
4
R
A
B
OUTA
OUTB
CC-
D
-------
2
–
4
3
R
4
(Gain Adjust)
(Offset Adjust)
12
+
+
45
B
V
+
R
OUTA
R
R
V
+
3
Bipolar “Window” DAC using R
5
45
CC-
V
45
R
R
R
⎛
⎝
R
1
3
R
----- -
R
5
3
2
1
⎞
⎠
V
OUTA
V
V
CC
CC
R
V
45
R
O
R
–
+
=
4
5
=
=
2.048V G
Offset Adjust Gain Adjust
------------------
R
V
0.1 µF
R
4
IN+
4
+
R
⎛
⎝
R
5
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
1
5
+
R
----- -
R
MCP4821/MCP4822
A
2
1
⎞
⎠
-------
2
D
12
–
A
4
V
V
V
G = Gain select (1x or 2x)
and R
CC
D = Digital value of DAC (0 – 4096)
AV
R
CC
OUTA
2
+
–
SS
3
, R
= GND
5
⎛
⎝
R
----- -
R
4
2
1
⎞
⎠
and R
5
are populated.
V
O
DS21953A-page 23