MCP4822 Microchip Technology, MCP4822 Datasheet - Page 27

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

6.5.1.2
When calibrating a set point or threshold of a sensor,
typically only a small portion of the DAC output range is
utilized. If the LSb size is adequate enough to meet the
application’s accuracy needs, the unused range is
sacrificed without consequences. If greater accuracy is
needed, then the output range will need to be reduced
to increase the resolution around the desired threshold.
EXAMPLE 6-2:
 2010 Microchip Technology Inc.
(a) Single Output DAC:
(b) Dual Output DAC:
V OUT
Thevenin
Equivalent
D
G
N
n
=
=
=
=
=
=
2.048 G
Gain selection (1x or 2x)
Digital value of DAC (0-255) for MCP4801/MCP4802
Digital value of DAC (0-1023) for MCP4811/MCP4812
Digital value of DAC (0-4095) for MCP4821/MCP4822
DAC bit resolution
Building a “Window” DAC
MCP4801
MCP4811
MCP4821
MCP4802
MCP4812
MCP4822

SPI
R
V
V

23
23
trip
SINGLE-SUPPLY “WINDOW” DAC
D
------
2
N
n
=
=
=
3-wire
------------------ -
R

------------------------------------------------------
V
V
-------------------------------------------- -
R
2
CC+
OUT
2
+
V
R
R
DD
3
R
DAC
R
3
R
R
1
2
23
2
+

+
+
+
R
R

23
V
V
3
23
CC-
V
R
OUT
1
R
3

R
1
R
R
2
3
V
V
V
CC+
OUT
CC-
If the threshold is not near V
creating a “window” around the threshold has several
advantages. One simple method to create this
“window” is to use a voltage divider network with a pull-
up and pull-down resistor.
concept.
MCP4802/4812/4822
R
R
SENSE
1
V
23
R
23
V
O
0.1 µF
V
TRIP
Example 6-2
REF
, 2V
Comparator
DS22249A-page 27
V
www.DataSheet4U.com
REF
V
CC+
CC-
or V
shows this
SS
, then